Master and starter solenoid diodes

[Frontier Fox]

I know that this topic has been reviewed several times and I have read all the posts, however I still need a little clarification. Someone posted a link that had all the info on this topic but it is no longer available. The FWF did not include diodes or a schematic. So can someone help me out with exactly what diodes are needed and how they are installed. Some pics would be nice.

Thanks in advance.:confused:

[Shadowrider]

Joe the diodes I used came with the Vertical Power install kit and how to install them is illustrated in the installation manual. I am no electrical expert but I think they are like a check valve for electricity and I think its to help protect against voltage spikes...but that is just a guess?

[4Hummer]

Post #19 in this thread has some pictures and discussion on what I did
https://teamkitfox.com/Forums/threads/10277-Mike-s-Kitfox-IV-rebuild

[Frontier Fox]

Thank you for the replies. Dustin, I understand what their purpose is but the way you describe the way a diode works is spot on.

4hummer, that’s a great pic and I like the way you put shrink wrap on, good idea.

i will need to put a diode on the starter solenoid also. The hard part is the way the solenoid is made. It doesn’t have a threaded stud on it for the actuator wire. It is a spade end. So I need to figure out how to address that without cutting the Rotax harness.

The rest of the wiring is pretty much complete. Next up is fitting the cowl. I’m sure I will be doing a nightly forum search before I’m finished with that step.

Thank you again.

[Delta Whisky]

Well this is a timely post - as I installed mine today. And, by the way, a diode came with the key switch in my SS7 kit; it mounts across the coil in the starter solenoid. Be aware that the diode on the starter relay attaches differently than the one on the master solenoid. On my master solenoid (relay), it looked like this:
24095

I bought 1N4001 diodes (Amazon, usually they come 5 or more to an order, $3 - $4 total) but now believe that may not have been the best choice. After a little more reading I found several posts that say you should use a diode rated for 10 times the system voltage (12 x 10 = 120V) and a current rating equal to the current thru the coil (from 1.3 to 1.5 A). So the 1N4001 might be a little weak (50V, 1A) but, then again, folks I found at several sites have been using them with good results. The band on the diode goes to the plus side of the coil. The unmarked end of the diode goes to the other end of the coil or ground. Quite often the wire to the master solenoid grounds it and the wire to the starter solenoid powers it so, again, where you make the connections are slightly different between the two devices.

[jrevens]

Hi Joe,

I just saw this thread... don't know if you still need any clarification or not. Arc suppression diodes are a good idea for any inductive load, like a relay coil. Not only master & start "solenoids", but other relays also, to protect the switch contacts in those circuits from excessive wear & tear or damage from the induced high voltage spike that can occur when the coil is de-energized and the high voltage arc jumps the gap in the opening switch contacts, like a miniature lightning bolt. Some relays do come with built-in arc suppression diodes, so you should check that before adding them to your circuits. Any number of common diodes could be used, but a popular choice is one of the 1N540X series (like a 1N5400). Diodes have an anode (+) and a cathode (-), and on many diodes the cathode (-) is identified by a band on one end. When used for this purpose, the anode (+) connects to the negative (-) terminal of the coil, and the cathode (-) connects to the positive (+) terminal. Don't reverse that or you'll make some smoke & destroy the diode. These diodes normally have solid wires, which isn't real good in a high vibration environment, so encasing the diode & wires in heat shrink tubing is a good idea - just be sure you can identify which wire is which. You could use clear tubing, or they could be tested with an ohm meter of course, but I like to cut the solid wire off a bit and solder stranded red & black pigtail wires, and then encase the diode & solder joints in heat shrink. The stranded wire is better for vibration flexibility & for installing ring or faston terminals also. You shouldn't use crimp-on terminals on solid wire - that's poor practice. You could combine the stranded wire on a diode with another wire inserted in the barrel of the proper size crimped faston terminal if you have "spade" (male faston) connections on your relay. Or you could use the little terminal adapters that connect on the one spade, giving you 2 (or more). There are also faston adapters that will give you a screw connection.

[jrevens]

I started writing my previous response, then got distracted with something else. After I came back and posted it I saw Darrel's post. Sorry for some of the duplication.