Ammeter/Voltage

[Bud Davidson]

Major milestone today. Finished the cowlings so was able to hook up the radiator. A couple quarts of nonalcohol auto fuel for a successful pressure and leak test so engine should run. Started on first compression. Wow, after sitting a couple years. Did pull plugs and scope the cylinders. Also, before final hookup of exhaust pipes I did check interior of exhaust ports, so I was somewhat confident the internals were ok. But... isn't there always a "but"!!

I am getting no charging from the system. Can I some way check power coming from the engine to the rectifier? And can I check output of the rectifier? Ammeter and voltmeter neither are responsive. Oil pressure, oil temp, water pressure and coolant temp good as is egt. All work when master switch is on.

I am totally lost in the electrical system jungle. Help!!

Engine sounds great. Carbs will need a little adjustment, but hooray for now.
Bud

[jrevens]

If you're talking Rotax, Bud, I believe you should be able to measure voltage (AC) across the 2 wires coming from the "magneto". Then, yes, you should be able to measure DC voltage from the regulator/rectifier, as long as both of those wires from the engine have an unbroken connection to it.

[Bud Davidson]

John,
I am running a Rotax 912.
I considered the suggestion you made regarding my earlier thread on electrical wiring. For now was intending to stay as wired be but may now have to reconsider.

If I understand correctly, I should be measuring alternating current across the two shielded wires from the engine to the rectifier.
Then the lead from the rectifier to the buss and on to the battery should be direct current measured across the common ground. Understood so far???

With the engine turning 2000 rpm I got no voltage increase at the battery in comparison to the battery without the engine running. I suspect that means nothing is coming from the rectifier. But first I will determine if any power is going to the rectifier. If not, then I have a connection failure or an inoperative dynamo. I hope it is a poor connection and will not be surprised if the rectifier is not working.
Thank you for your thoughts on this.
Bud

[HighWing]

On my first Model IV build, I got no charging current from the rectifier. I did as you have done and asked the guys. What I had neglected to do is ground the rectifier thinking the two in and the two out was all it needed. I added the ground wire and presto. At least this is what I recall.

[rv9ralph]

Don't forget to add the capacitor to the circuit.

Ralph

[jrevens]

John,
I am running a Rotax 912.
I considered the suggestion you made regarding my earlier thread on electrical wiring. For now was intending to stay as wired be but may now have to reconsider.

If I understand correctly, I should be measuring alternating current across the two shielded wires from the engine to the rectifier.
Then the lead from the rectifier to the buss and on to the battery should be direct current measured across the common ground. Understood so far???

With the engine turning 2000 rpm I got no voltage increase at the battery in comparison to the battery without the engine running. I suspect that means nothing is coming from the rectifier. But first I will determine if any power is going to the rectifier. If not, then I have a connection failure or an inoperative dynamo. I hope it is a poor connection and will not be surprised if the rectifier is not working.
Thank you for your thoughts on this.
Bud

As Lowell stated, be sure the regulator is well grounded to the airframe/electrical system. If you are depending an a wired connection for that, make sure it's at least #12 awg, like the wires coming from the dynamo (I don't know why I said "magneto" earlier - "old-brain syndrome", I guess).

[Bud Davidson]

Problem solved. Circuit check disclosed volt meter and ammeter connected to radio buss instead of master buss.
Wire grounding rectifier is same size as wire to starter from the battery and starter to ground. (6 awg ).
Engine produces 20 Volts AC at 2500 rpm. 12 Volt DC is 13.6 Volts and slightly over 5 Amps.

Now all that is the good news. The bad news will probably stem from the white smoke and brown liquid that poured from the capacitor after about 30 seconds. It sizzled a lot also. I cut both wires and after that everything seems ok. No electronics installed right now fortunately I suspect. Will trace capacitor wiring after I return from Sun n Fun.
Thanks again for all the suggestions.
Bud

[jiott]

Bud, you definitely dont need a #6AWG ground wire to your regulator housing. As John said a #12 is plenty. I think I used a #14 .

[jrevens]

Problem solved. Circuit check disclosed volt meter and ammeter connected to radio buss instead of master buss.
Wire grounding rectifier is same size as wire to starter from the battery and starter to ground. (6 awg ).
Engine produces 20 Volts AC at 2500 rpm. 12 Volt DC is 13.6 Volts and slightly over 5 Amps.

Now all that is the good news. The bad news will probably stem from the white smoke and brown liquid that poured from the capacitor after about 30 seconds. It sizzled a lot also. I cut both wires and after that everything seems ok. No electronics installed right now fortunately I suspect. Will trace capacitor wiring after I return from Sun n Fun.
Thanks again for all the suggestions.
Bud

This issue with the capacitor has come up on this forum before, Bud. It's quite possible you have the capacitor wired backwards - negative to positive and vice versa. Electrolytic capacitors are polarity sensitive.

[Av8r3400]

If the capacitor is wired backward, it will explode.

Don't ask.

[efwd]

Awe Man, hope I remember this when its my turn. Sorry to hear Bud. Hope thats an inexpensive part.
Eddie

[Bud Davidson]

If wired backwards it WILL explode !!!.
Any suggestions about where is the best source for a capacitor of that size?
Bud

[Av8r3400]

I got mine off amazon...

[colospace]

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