My green gear down and yellow gear up lights in my PA30C recently stopped working. The white in-transit light works fine. In tracing the wiring against the schematic in the maint manual (Fig 11-63b), I found what appears to be a regulator (probably a Darlington circuit with a control and power transistor) wired to the dimmer rheostat.

Two questions:

1) Has anyone ever seen this regulator before? Looks like it might have been added to allow more lights (more power consumption).

2) Does anyone know the actual schematic diagram of the dimmer rheostat/switch? The Figure in the manual just shows two square boxes with NO internal wiring.

Frank,

I'd suggest contacting Mat Kurke at http://www.comanchegear.com/gear%20problems.php I view him as an authoritative source. Below is simply my thoughts and may or may not be your problem.

IIRC the gear down light operates when all three gear micro-switches are closed and the up light operates off the up-limit switch. I believe the in-transit light works when the motor runs. Since my Twin did a belly slide when the micro-switches were improperly adjusted to show a false positive green gear light by a seasoned Comanche mechanic, I am concerned for you - especially if they quit working after a maintenance event.

Please post the resolutions so we can all learn. Thanks.

Frank,

Found this page which may also have some helpful thoughts. http://www.comanchegear.com/discussions.php

Ask Matt! That does not look factory to me.

Thanks Kristin and Pat. I have talked to Matt briefly, and he doesn't have a colored diagram for the PA30 (just the PA24). Gave me the suggestions as he has posted on his website.

I have the rheostat and "regulator" out, and am now tracing the PLUS voltage on each light, as well as the ground for the gear-down light (haven't put the plane on jacks yet to test the gear up ground, but it seems fairly straight forward.

Since neither light works, it suggests to me it's in the PLUS voltage side of things. With the regulator remove, I need to trace things back to the raw voltage at the bus bar. Something to keep an olde retired electrical engineer busy on non-flying days! I'll let you know what I find.

That regulator is definitely not in the wiring diagram for the PA-30 and there was no such in my aircraft which is also a PA-30C. I am assuming you ruled out a common ground for both lights. The grounding in my aircraft was a nightmare until I redid it. There was one long screw with 27 ground terminals on it. Most regrettable!

I'll check the common ground issue; could be a faulty insulating washer.

The "regulator" has a S/N on it, but no manufacturer, so I figured it wasn't PMA'd. There is a landing light flasher unit installed, but it wouldn't have anything to do with the dimmer circuit.

So onto my back and under the panel again.

Being an EE is sort of 'cheating' isn't it? Just kidding. So glad you have those skills. Don't envy you working behind the panel but good flying weather is coming ...

The lights are working again!

By removing the mystery regulator and dimmer rheostat/switch from the circuit, and connecting the Dimmer input wire to the Dimmer output wire, all is well. Though I can't dim the lights, that's not a problem with the landing gear lights, as I prefer to ALWAYS have those at full brightness.

Thus, the problem is in the mystery regulator, which didn't belong there in the first place!

Frank, glad to hear the lights are working again. For me, I'd want the dimmer in there somewhere - perhaps it is not a factor for you.

Hi Frank,

Glad you got it working. As an aside I have always felt the best thing about Matt's landing light kit is the option to take the lights out of the dimmer circuit. No more panic on a day flight after a night flight.

Don

PS The lights in the kit can be dimmed manually although I have never done it. I don't find them distracting at night.

I agree Don. I choose NOT to dim the landing gear lights, after all the horror stories of gear-up landings, or thinking the gear didn't come down, when in fact, it was the dim lights all along. And since the landing gear lights are buried down by your knees, they don't bother me a bit.