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cap01
04-10-2012, 07:49 PM
I agree with dorsal , the addition of left and right mag toggle switches in parallel with the key switch is well worth the time .

Av8r3400
04-10-2012, 08:19 PM
The guys from both LEAF and Lockwood say repeatedly that the ACS ignition switch (Off-Left-Right-Both-Start) should not be used with the 912 engines. These switches are not designed to handle the ac voltage that the ignition system sends through them, they are designed to ground magnetos.

According to LEAF these switches are responsible for more ignition box failures than anything.

(I'm still running one, too, so this should be warning to me as well... :eek:)

Dorsal
04-11-2012, 03:50 AM
I agree with dorsal , the addition of left and right mag toggle switches in parallel with the key switch is well worth the time .

Actually I only added a start button, still use the key for L-R-Both, not sure if that helps with the issues identified by LEAF and Lockwood.

jtpitkin06
04-11-2012, 08:16 AM
Re: Magneto switch and Rotax

Larry,

I wouldn't worry about your mag switch.

There are some sites that say a “standard” mag switch cannot handle AC current from the ignition shorting wire on the Rotax 912. This is probably not correct.


In fact, any switch designed for DC can handle a much higher voltage and current when used in AC. The limiting factor on switches is arcing of the contacts. When a DC switch opens the current continues to flow across the gap until the air resistance is high enough to break the connection. It is the continued arc that causes switch contacts to burn or pit.



In AC circuits the current is constantly reversing. Each time the current reverses the voltage drops to zero. When the voltage drops the arc is temporarily stopped. Restarting the arc takes a much higher voltage for a given air gap, thus the arc is broken sooner than it would be with a DC circuit. Less burning and less pitting with AC.


A switch can often handle 10 times the voltage and 50 percent higher amperage on AC that it could on DC. Many switches have voltage rating printed on them. A typical rating might be AC 250 volts at 6 amps and DC 28 volts at 4 amps.


The Rotax “kill” wire shorts the low voltage input side of the ignition module, not the high voltage output. That voltage is about 40 volts at maximum which is comparable to a magneto P lead voltage.


The Magneto ignition P lead is not pure DC either. It is pulsed, starting at zero and rising to peak then falling back to zero on each opening of the points.



The contacts in a “standard” magneto key switch are very robust and can handle AC voltages far in excess of anything put out by the Rotax dynamo. If you install toggle switches, you may actually end up with a switch that is less reliable than what you have now.



I would continue to use your magneto key switch with confidence.


John Pitkin
Greenville, Tx

jiott
04-11-2012, 10:00 AM
What is the key switch that Kitfox sells in their parts catalog? I assume it is fully compatible with the Rotax 912.

Jim

Av8r3400
04-11-2012, 10:48 AM
John - with all due respect, the information I passed on was from several people I have heard speak and have spoken to directly, not random "internet experts". People like Phil Lockwood and Brian Moyerhauser from LEAF, who I have heard address this directly, are far more expert on this subject than you or I.

Both of these gentlemen have stated that the ac voltage is sufficient to erode the contacts in these switches which causes a feedback through the Ducati ignition boxes which can cause damage. Both of them recommend individual, heavy duty, 250v ac switches for the ignitions. A security, keyed switch can be used elsewhere for the start and/or master functions.

Your Corvair automotive ignition is most likely different and this may not apply. As to the 912 ignition system I plan to head this advise.

jtpitkin06
04-12-2012, 11:12 PM
My local airport is KGVT, Greenville, Texas. It is home to the defense contractor L3 – Mission Integration Systems. L3 employs thousands of engineers. I am fortunate to rub shoulders with many of these engineers both active and retired.

I spent much of the day with a pilot/electrical engineer who has over 35 years designing and specifying aircraft electrical systems. We discussed the magneto switch when used with the Rotax Ducati ignition system. He agreed the notion of a magneto switch causing a failure of the solid state module with some type of "feedback" was poppycock. He also agreed the AC voltage on the Ducati kill circuit was less damaging to a switch than the P lead circuit on a magneto ignition.

Let’s look at the facts, how the system operates, and possible failure modes.

The Rotax Ducati ignition uses a shorting wire to “kill” the ignition. It is only grounded on engine shutdown and during ignition checks. The shorting wire is grounded through the “mag” switch. If the shorting wire is disconnected or breaks, the engine continues to run. The only electrical things that could damage the ignition module are overvoltage and improper or shorted wiring.

The Rotax engine dynamo supplies power to the modules. Voltage is limited by engine rpm. Current is physically limited by the size of the dynamo coils. It is impossible for the dynamo to supply excessive voltage or current to the modules. The vast majority of Ducati ignition module failures are wires breaking inside the insulation close to the module due to vibration.

The premise that AC voltage present on the grounding circuit is too high for a magneto switch is unfounded. The voltage involved when grounding a Ducati module is similar to the voltage present on the P lead of most magnetos. The internal arcing with AC voltage is less than what would be present with a pulsed DC signal from a magneto. There is no reason to assume one or more toggle switches will last any longer than a standard magneto switch.

While we have no doubt some standard type magneto switches have failed while in service on the Rotax engines, we do not believe they are the cause of ignition module failures. If the contacts on the magneto switch were to corrode or burn to the point where they no longer make continuity, the respective module would simply not shut down with the switch in the off position. I don’t think LEAF, Lockwood or anyone else can explain how an open kill circuit due to a bad switch is the cause of ignition module failure.

Advising aircraft owners to change the magneto switch to toggle switches is questionable. The magneto switches are aircraft quality devices with large contacts capable of handling high voltage and current loads either AC or DC. Magneto switches are used successfully on many Rotax 912 equipped aircraft without incident. The replacement toggle switches are largely unspecified. A 250 volt toggle switch can be a totally inadequate miniature device capable of only 0.5 amps. with quality or origin unknown.

In summary, the Rotax Ducati ignition module kill circuit is not likely to damage a magneto switch or a replacement toggle switch. Nor is any switch, magneto or toggle likely to cause a failure of the ignition module.

John Pitkin








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cap01
04-13-2012, 07:45 AM
Thanks John for clearing that up , I was having a hard time understanding how the open contacts of a mag switch could cause problems with the module . The rotax installation manual does give a 250 volt .5 amp spec for the mag switches . Granted there are quality issues out there with so much crap from china . Thankfully there is some mil spec stuff still available.
There are advantages to having both the toggle switches and the keyed switch . For the times that require motering the engine without starting it ,such a purging the oil system also no chance of bumping the starter while doing a mag check using the toggle switches

wwillyard
04-13-2012, 04:38 PM
I used the ACS switch for a number of years with no problem until about a year ago. The ACS switch failed when I was trying to start my 912ul by erratically grounding the ignition modules while cranking causing the propeller to stop dead in it's tracks. The first time this occurred I suspected that the battery was getting weak, so I replaced it. The next time this problem occurred I was unable to obtain an engine start. Determined cause to be ACS switch by leaving it in the "Both" position and jumping the start circuit beyond the ACS switch, instant start with smooth operation. I have since replaced with 250V toggle switches and a momentary push button for the starter. Now all starts are quick and smooth.
I originally thought that there is no reason the ACS switch shouldn't work just fine as it appears to be constructed with heavy duty contacts. I disassembled the switch after failure and it looks like new inside, but there is definitely a problem when used with the Rotax ignition modules.

Av8r3400
04-13-2012, 07:25 PM
I consider LEAF and Lockwood experts on Rotax engines. They have years (decades) of experience with these engines in particular. I have added the switches on my plane and replaced the ACS switch per their advise. This thread has brought it to the front burner for me, so I did the conversion.

Everyone has the free choice to do this or not.

jiott
04-13-2012, 10:41 PM
I am still wondering about the Kitfox supplied ignition switch in their catalog as a asked a little ways back in this thread. It doesn't give any specs. I keep hoping John McBean will reply about it. Also wondering what Kitfox uses in their SLSA?

Jim

av8rps
04-17-2012, 05:25 PM
I have two friends with Just Aircraft 912s powered Highlanders that had rough running engines that NOTHING fixed. Finally Brian from Leading Edge told one of them to get rid of that ACS switch, and like magic, the problem was cured. So my other friend did the same to his Highlander, and saw the same result.

Ironically, I purchased a Highlander last year that has a little over 200 hours on it, and it runs much rougher than does the 912ul in my Kitfox. I initially blew it off as probably being caused by my 2 blade sensenich prop, but after trying a Warp on it I got the same roughness. I haven't replaced the ACS switch yet with toggle switches, but will be doing so as my next step. Both of my buddies are insistent that is the thing to do since it did so much for their 912's.

Oh, and both of them use the ACS switch for operating the starter. They've just eliminated the mag leads from the R and L positions and replaced them with high quality toggle switches.

I can understand where an electrical engineer might not agree with the voltage statement discussed earlier in this thread. I could be wrong, but I think the problem with the ACS switch is a poor quality contact causing intermittent contact for the mags, essentially causing an erratic on-off-on-off situation for the mags (and therefore rough running engines too). I wouldn't think that would be any too good for these rather sensitve (and did I mention EXPENSIVE) 912 electronic ignition boxes.

So John and Larry, I think you are both right :)

jdmcbean
04-17-2012, 07:05 PM
OK.. I tried staying out of this one.

We (Kitfox) and I personally have years and decades of OPERATIONAL use of the key switch. Any switch can and has failed, be it a toggle switch or a key switch. The wiring and or connector that is used is most likely the issue.

Our S-LSA aircraft use this same switch without issue and one of them is operating in a training environment with over 1400 hours in the last 2 years. Along with 1000's of other aircraft including ours personally.
I recently changed our aircraft to using toggles and a push button start because I like that setup not for any other reason.

Specifically, regardless of the style of switch the Rotax "mag" is simply going to ground. If it grounds it's off.. if it doesn't it's hot. The switch specs required according to Rotax are Min 250V .5A which the ACS switch meets.

While I personally consider LEAF and Lockwood professionals and I'm sure they have seen switch failures. I would challenge them or anyone regarding this issue. While anything can happen, it is unlikely that a switched "mag" wire to ground is going to cause a module failure.

I suspect that some may have had switch failures.. while others may have had a wire or connector issue (more likely).

On that note: We are looking at other alternatives... the ACS keyswitch is simply expensive.

Slyfox
04-18-2012, 06:45 AM
good response John. I have the same thing. throw switches for the mag. there is no way I would do differently. allows me to turn the engine over with mags off. Good for many things, like getting oil pressure after oil change, making sure there is good oil pressure before the start, getting a good choke before first start. I have a key switch for starting and that switch is from 95. If that goes out I will do the push button. I have that setup on the RV and love it.

jiott
04-18-2012, 11:27 AM
Could someone post a simple wiring sketch for the setup with toggle for mags and keyswitch for starting. This is probably a dumb question, but I am not very confident in electrical issues and need to start learning real soon since my panel build is coming up.

Jim

Dorsal
04-18-2012, 04:38 PM
Whether you use the key for starting with switches for the mags or use the key for the mags and a push button for starting I do like having a key (that can be removed) somewhere in the system. As others have said I also like being able to turn the engine over with the mags off so I can use the Slyfox starting method :D among other things.

cap01
04-18-2012, 07:33 PM
I don't have a picture handy but the rotax installation manual has all the diagrahams you'll need also specs for wire and switches . Only the wire sizes are in mm not awg .

jtpitkin06
04-19-2012, 06:04 PM
The discussion of the ACS switch with other engineers put me in contact with an owner of a homebuilt (not a Kitfox) with a Rotax 912. He had experienced an ignition switch failure and replaced it with toggles. Did he still have the bad ACS switch?

Yes! was the answer.

Great! Let’s have a look inside to see what happened.

The first picture is of the switch as removed. It is an ACS products A-510-2 manufactured on Jan 31, 2001. It has off-right-left-both-start positions.

Upon opening the switch we found a burned contact. But the evidence shows the contact was burned from arcing in the start circuit, not from the ignition grounding circuit.

The next two photos show the burned contact on the rotor and the switch plate.

Seeing the location of the burn in the start circuit I suspected emf surge may be the culprit. I asked, “Do you have a diode across the starter solenoid?”

“A what?” was the reply.

A diode across the start solenoid prevents a surge of current from the starter solenoid (relay) from racing backwards through your electrical system. A diode is like a check valve. When the starter switch is activated the electrical energy goes through the coil inside the solenoid creating a magnetic field. The magnetic field closes the high current contacts for the start motor. When you release the start switch the magnetic field in the solenoid collapses and stored electrical energy races backwards toward the switch. (If this sounds familiar, it is how an automotive ignition coil works.)
A diode allows the stored energy to bleed off harmlessly instead of frying your starter switch.

Without the diode the reverse current enters the start switch and jumps across a gap to the ground terminal creating an arc and burning the points. This is the same surge that loves to fry your radios on engine starting. Your instructor did teach you to have the radios off when starting, right?

So how does this affect the ignition?

The design of the ACS switch uses 3 sliding contacts for multiple functions.

In the start position one slider connects the battery to the starter relay. That same slider is used for grounding the right mag when left mag is selected and it grounds the right mag differently when off is selected.

Due to the construction, the burned contact cannot cause an inadvertent grounding of the mags to off, but it can cause a failure to shut the ignition off leaving the right ignition hot. This type of failure would show no mag drop when selecting left mag during a test. It is also possible the engine would still shut off normally because the slider uses different contact points when off is selected. It is important to remember the switch does not turn the ignition on. It can only turn it off by grounding.

There are several possibilities for those wishing to improve on the system.
First is to ensure you have a diode across the start relay. Be sure to hook it up with “reverse bias” Positive to negative and negative to positive. Put the end with the stripe on the positive terminal. A Radio Shack diode 1N4001 with a 1 Watt rating works well.

If you have a diode installed and everything works fine, you may wish do nothing and fly with the standard mag switch happily ever after; or,

You may chose to replace the ignition/starter switch to a keyed switch without the start function and use a separate starter button. This option allows engine cranking without the ignition; or,

You may retrofit to separate toggle switches for ignition and use a keyed automotive/marine type switch for just the starter. This option also allows engine cranking without the ignition while you still have a key; or,

Eliminate any key switch in the system and just go with toggles for ignition and spring switches or pushbutton for start.

Something for everyone.

This post is a bit long, so… whether you want to flame me or send kudos, (I don’t care which,) please don’t quote the entire message. Trim the post and just quote the part that makes you bubbly happy or boiling mad.

Regards,
John Pitkin

Dorsal
04-19-2012, 06:16 PM
Makes sense to me :)

szicree
04-19-2012, 06:30 PM
Good stuff, John. I built my RV-4 with toggles and a pushbutton (and a diode), figuring that a motivated thief could easily get past the key switch anyway. It occurs to me now that the propellor of an unattended plane with only a pushbutton poses a potentially lethal risk should some bonehead reach in and start pushing buttons. I know it's unlikely, but if some idiot accidentally chops his friend to bits with my prop I know exactly who'll get sued :eek:. I think this build will have a keyed switch somewhere in the system.

av8rps
04-19-2012, 07:17 PM
The discussion of the ACS switch ....snip.... He had experienced an ignition switch failure and replaced it with toggles. Did he still have the bad ACS switch? Yes!..snip...
John Pitkin

John,

That is an EXCELLENT post! And it makes perfect sense with what has been happening. Thank you for sharing that information. I am going to share it with my friends as we all wondered why the problem was happening. Now we know.

Dorsal
04-19-2012, 07:32 PM
Good stuff, John. I built my RV-4 with toggles and a pushbutton (and a diode), figuring that a motivated thief could easily get past the key switch anyway.

More than once I have boosted some big eyed kid into the pilots seat after seeing them watch from the fence. It always puts a big smile on their face (and the grateful parents) but only if I have the key in my pocket.

Esser
04-20-2012, 03:01 AM
Good stuff, John. I built my RV-4 with toggles and a pushbutton (and a diode), figuring that a motivated thief could easily get past the key switch anyway. It occurs to me now that the propellor of an unattended plane with only a pushbutton poses a potentially lethal risk should some bonehead reach in and start pushing buttons. I know it's unlikely, but if some idiot accidentally chops his friend to bits with my prop I know exactly who'll get sued :eek:. I think this build will have a keyed switch somewhere in the system.

Simplest fix for wanting a key some where is if you have easy access to your battery put on a locking master switch on your battery.
http://www.narva.com.au/sitebuilder/pressreleases/knowledge/asset/medium/21/20-march.jpg

Dave S
04-22-2012, 03:55 PM
John P - Regarding the photos of the burned contacts

Were you able to determine exactly what kind of metal the contacts are made of? Almost looks like aluminum??? I know photos often don't show the colors well; but, on the photos of the contacts they certainly don't look like copper, brass or gold to me.

Also - was there any type of lubricant on the contacts when it was originally opened up?

Thanks,

Dave S

jtpitkin06
04-23-2012, 07:48 AM
The contacts in the ACS switch appear to be silver plated brass. The switch shown is notable in that it is one of the later manufacture dates with the identifying red paint in the screw heads. It is not subject to the AD for periodic lubrication but it did have lube inside.

I have the same switch in my Cessna. It too is a later model and I have a diode in the start circuit. The AD requires that I check the switch is functional in the OFF position. I may open the Cessna switch on the next annual just to have a peek at the contacts.


John Pitkin

jrevens
05-07-2014, 08:27 PM
A recent series of conversations with a friend & fellow builder, have brought this issue to mind again. I'm probably just beating a dead horse at this point, but I have a couple of thoughts/theories on this subject that I'd like to share with the group.

Regarding the possibility of these ACS keyed switches somehow causing the failure of a sensitive ignition module - since these switching contacts are located in the same enclosure & relatively close to each other, I wonder if there is a possibility of the high voltage back emf, produced when a non-diode protected starter solenoid coil is de-energized, "jumping" the gap or perhaps following a slightly conductive "trace" (caused by previous arcing) from the starter coil contact to one of the ignition contacts, effectively "zapping" an ignition module.

The second thing I'd like to present is that having a switch with a high enough current & voltage rating does not always make it an ideal choice for a low voltage, low current application (such as, perhaps, an ignition grounding switch). It is fairly common to have cadmium-silver plated contacts on high quality switches, and these contacts are sometimes not recommended for use with low voltage &/or current. The reason is because there is not enough (or any) arcing that occurs during use, and some arcing has been found to be desirable or necessary to keep these contacts from slightly oxidizing & creating an abnormal amount of resistance when "closed". This is probably not the case with the ACS switches, since they have a sliding contact action... I don't know.

I'm using a small key switch for start, & 2 toggle switches for ignition (similar to the way that Van's does it with the RV-12) on my Kitfox.

GWright6970
12-01-2017, 06:17 PM
Could someone post a simple wiring sketch for the setup with toggle for mags and keyswitch for starting. This is probably a dumb question, but I am not very confident in electrical issues and need to start learning real soon since my panel build is coming up.

Jim

I wish to second Jim's request!

It would be awesome for us NON-ELECTRICAL TYPES to have a diagram showing how to incorporate the two toggle switches into the Kitfox factory diagram using the ACS switch!

I am particularly interested in how and where the shields of the two ignition wires are grounded in such an installation.

HUGE THANK YOU!
Grover

Av8r3400
12-01-2017, 07:52 PM
I'm a little confused by the shielding part of your question.

The brown wire from each module is what is switched (to ground) to turn off the ignition module. From what I can see in the books, these are not shielded wires.

jrevens
12-01-2017, 08:44 PM
Hi Grover,

I think you'd find a lot of useful information about this in the "AeroElectric Connection" by Bob Nuckolls, if you haven't already looked at that. I'll try to explain how he has suggested wiring that circuit. It's probably the simplest circuit on the airplane, so my long explanation will probably be over-kill. You can use single-conductor shielded wire for each ignition module. 16 or 18 gauge would be fine. I used 18 gauge. While shielding isn't necessary on these circuits, and even 18 gauge is bigger than it needs to be, that type/size of wire was suggested for robustness, as well as being able to cleverly use the shielding as the ground conductor. So, a pigtail is attached to the shield on each wire, and each pigtail goes to it's respective common terminal on an ignition switch (toggle, rocker or whatever). Each center conductor attaches to the N.C. terminal of it's switch. At the ignition module on the engine, the center conductors of those 2 shielded wires each goes to it's respective pin on the module connectors (the brown wire mentioned by Larry - refer to Rotax manual). The shields from your 2 wires are then connected to a grounding point ON THE ENGINE, again with pigtails. So, when a switch is "off", contact is made between the common and N.C. terminals, which connects the ignition module pin, through the center conductor to the switch and from there through the shield back to ground at the engine. When a switch is "on", that pin is disconnected from ground as the N.C. contact becomes "open". Again, you don't have to use a single conductor shielded cable - you could use a 2-conductor un-shielded cable for each module (or other combinations of conductors with or without shielding if you wanted to), but the shielded cable is generally a little tougher and more resistant to intolerable damage. It's a nice, clean way to do it, and you've also got shielding, whether it's needed or not.

SS7Flyer
12-02-2017, 12:17 PM
You can run a very simple on-off-start ignition switch when using toggles for the ignition boxes.

jrevens
12-02-2017, 08:28 PM
You can run a very simple on-off-start ignition switch when using toggles for the ignition boxes.

You can run an even simpler momentary contact on-off keyed switch for the start function, along with the ignition switches. That happens to be how they do it in the RV-12s, and that's what I did too. In fact I used the same compact, light weight switch that the RV uses too... pretty much like what is used on many alarm systems. The 2 ignition toggle switches are completely separate from that start switch. Which ever you use, you want to be sure to use an arc-suppressing diode on the start solenoid/contactor coil circuit to protect the contacts in the start switch from a possible large back emf pulse created when the coil is de-energized and the magnetic field collapses.

Flybyjim
12-02-2017, 09:27 PM
I am building the ss7 but have not yet ordered the firewall forward kit, is this not all included with this kit?. I would like to think Kitfox has these answers all worked out with this kit. The last kit I built, not a Kitfox had all the parts supplied with the two toggle switches and a start key switch.

jrevens
12-02-2017, 10:29 PM
I am building the ss7 but have not yet ordered the firewall forward kit, is this not all included with this kit?. I would like to think Kitfox has these answers all worked out with this kit. The last kit I built, not a Kitfox had all the parts supplied with the two toggle switches and a start key switch.


My kit came with a standard ignition/start key switch made by ACS - a copy of the original Bendix switches. Some of us prefer to have separate switches for ignition and start, rather than the combo switch. There are people who claim to have had ignition module failures that they attribute to the combination switches, including at least one well-known Rotax supplier. This has been discussed on this forum in the past, Jim. There are some other advantages to having separate switches also.

GWright6970
12-02-2017, 10:41 PM
John,
I purchased Bob Nuckolls' 12th Edition from him. It REALLY helped me with a lot of things, but I needed a diagram better than his Rotax 912 Figure Z-16; with Notes 2 and 3 not helping much to clarify things. I have no idea what that box is that the ignition module wires go to...I have a guess, but I hate guessing!

I have been blessed by two builders who have allowed me to photograph their flying aircraft. In one of these aircraft the ACS OFF R L BOTH START switch is also installed with two toggle switches. On the other side of the panel, the ACS switch is clearly wired to the R and L contact points with wires appearing to be coming from the two toggle switches next to it. I am guessing that the toggle switches are installed in series between the ACS switch and the ignition modules. I do NOT see shielded wires... Much less the shielding being grounded. This got my curiosity really going to say the least....hence my original question.

I have read and understand both sides of the ACS switch debate. I also have listened to discussions on the benefit of turning over the engine without the modules "on." I wish to therefore use BOTH the toggle switches and the ACS switch. I do have the ACS diode to install on the starter solenoid.

(So I also gather that the shields are to protect the modules from electromagnetic compatibility and electromagnetic interference that can be introduced by the brown ignition wires.)

SUMMARY
From what I now gather from my Rotax 912 Installation Manual and your reply, I can run a shielded wire from each module to it's toggle switch, connecting the shields as described.... The ACS would then be wired as shown in the Kitfox manual except that the two "brown ignition" wires are attached to the toggle switches instead of the ACS switch. I will also install the diode.

Thank you!!!

jrevens
12-02-2017, 11:03 PM
You're welcome, Grover. Just one additional comment - I probably wasn't clear enough, but shielding is probably not needed on the ignition wiring for these Rotax engines. Again, the shielded cable is a little more robust and perhaps less vulnerable to serious damage than un-shielded cable. It's nice to be able to use the shield for the ground path on those particular circuits is all, and additionally you have shielding whether needed or not... (just in case?). FWIW, I wouldn't be a fan of using extra switches in series with the combination switch contacts. You're just introducing another potential failure point in the circuit, with no advantage at all that I can see. You would have 4 sets of contacts that have to be made instead of just 2, in order to make sure your engine is "safe" from accidental ignition. Simpler is better in this instance, IMHO. It sounds like you're not going to do that, and I believe that is what you are saying in your summary... that you will use the ACS switch, but just not use the ignition switching feature of it, only using it as a start switch. Is that correct?

GWright6970
12-02-2017, 11:25 PM
(?... that you will use the ACS switch, but just not use the ignition switching feature of it, only using it as a start switch. Is that correct?)

John,
You are correct. I will NOT be running the module brown wires on to the ACS switch. I will run the module wires to the toggle switches ONLY.

I will be using the shielded wire and grounding both ends... Even though I read an EAA Sport article that said to ground only one end.

Again, thank you!

jrevens
12-02-2017, 11:31 PM
(?... that you will use the ACS switch, but just not use the ignition switching feature of it, only using it as a start switch. Is that correct?)

John,
You are correct. I will NOT be running the module brown wires on to the ACS switch. I will run the module wires to the toggle switches ONLY.

I will be using the shielded wire and grounding both ends... Even though I read an EAA Sport article that said to ground only one end.

Again, thank you!

OK, that's good... except- you DON'T ground both ends. The engine end is the only connection to ground. The other end goes to the switch.

GWright6970
12-02-2017, 11:47 PM
John,
Ok... I have a shielded wire. I place a molex connector on one end on the internal wire conductor and slide that pin into the molex 6 pin connector.

I take the other end of this shielded wire, and place a terminal on the internal wire conductor, and then this end is connected to a toggle switch leg.

I then install a pigtail from the shield on the end near the module and land that on a ground near the modules. The shield on the toggle end gets a pigtail attached and the pigtail is grounded to the switch housing.
(That takes care of the wires between the toggle switches and modules.)

I take a different wire, place a terminal end on each end; and connect one end to the other toggle switch leg, and the other end goes to the ground connection.

Does this work?

GWright6970
12-02-2017, 11:52 PM
Only a few more wires to go!

Thank you everyone!! Huge thanks to you John!

jrevens
12-03-2017, 02:10 AM
John,
Ok... I have a shielded wire. I place a molex connector on one end on the internal wire conductor and slide that pin into the molex 6 pin connector.

I take the other end of this shielded wire, and place a terminal on the internal wire conductor, and then this end is connected to a toggle switch leg.

I then install a pigtail from the shield on the end near the module and land that on a ground near the modules. The shield on the toggle end gets a pigtail attached and the pigtail is grounded to the switch housing.
(That takes care of the wires between the toggle switches and modules.)

I take a different wire, place a terminal end on each end; and connect one end to the other toggle switch leg, and the other end goes to the ground connection.

Does this work?

Sorry... no. It works, but not as I described.
OK, here we go... you have two ignition modules and they will both be wired the same way, individually, with 2 separate, shielded single conductor cables. To do it as I described (as per Bob Nuckolls) you are not going to ground anything at the panel on these circuits. You use the shields as a conductor to ground at the engine, not specifically just as a shield grounded at the engine, as you describe. The center conductor goes to the ignition module on one end, and to a switch terminal on the other end. The shield goes to the ground at the engine (like you said) and the other end of it goes to the common terminal on the switch (with a pigtail also). There is no additional wire going to a switch terminal, and again, no grounding at the panel or “switch housing” on these particular circuits. Then of course, the switch needs to open the circuit when it is “on”, and close the circuit when it is “off”. I guess you could say the object of doing it this way is to ground the module remotely at the engine, with a switch at the panel. You could do the same thing with a simple 2 conductor cable, but this way uses the shield as one of the conductors, so that it does “double duty” by acting as a shield, grounded at only one end (the engine), when the switch is “open”.

GWright6970
12-03-2017, 07:51 PM
John,
Ok...now I got it!!

Thank you for your patience... The Rotax drawing shows grounding everywhere... I got caught up in that drawing.... This way is simple!

Cheers!

wiggy
01-14-2018, 10:46 AM
14960

This is a ACS wiring for grounded Bendix mags. I’m working on a Kitfox that is not wired like this. Terminal 3 and 4 were reading ground. Terminal 5 was open.

I’m struggling to understand the Kitfox drawings, the existing wiring in the plane, and the new installation instructions for a 912 ULS.

I’m ok with the L and R mag wires being shorted to ground with the ignition in off position, but are these also the two brown wires that deliver 12v to Module A & B (I think pin 5). I can easily understand pulling the hot signal off of the starter solenoid to supply power to the (violet) wire for Soft start - now called easy start.

Help please?

jrevens
01-14-2018, 11:00 AM
I’m not close to the airplane or my wiring diagrams, but will just say that other than the 12v. signal from the start solenoid coil for the easy start function (which you seem to be clear about), there is no power supply to the modules from the ship’s power at the panel. The modules are powered directly from a dedicated coil section on the engine’s “dynamo”. That wiring is already installed on the engine by Rotax.