Popping NAV and Landing light switches

[Jeev]

Last night when I was getting night current my landing light and nav light rocker switches would just pop off on random times.  I was flying with the nav lights for about an hour with out a problem but as soon as I turned on the landing light and fuel pump near the airport it would happen. 

Any ideas? Thanks.

[Carl S]

I would try to isolate it to the fuel pump or landing light. Dig up your electrical schematic and then try to replicate the results on the ground with just the fuel pump or just the landing light.  If you can isolate one of those in conjunction with the nav lights as the culprit then you can get out the multi meter and try to find the short.  Doing that yourself can save a couple hours of labor charge with the A&P before you take it in. If your mechanic will supervise you at a reduced rate, all the better. You get to learn some of the ins and outs of your machine and get mentoring. If your time is worth more than shop rates you could just take it in.  I would want to suss this out before flying again though, especially at night.

Carl

[Jeev]

Thanks - Flew around this morning for 1.6 and could not replicate the issue

[Stefanovm]

I found that I have about the same problem this morning. My fuel pump does not change what happens. I can use just nav lights and they go off in 2 to 5 minutes. Same with the landing light except time is about 1 to 2 minutes. Adding or subtracting load does not change much and battery voltage is always good at 14 V when it happens. Mine are toggle type switches. I plan to check amp draw on both this weekend. It does not act like a dead short, but may be a short jsut the same. I am hoping that the problem is not bad switches, as getting them and changing them appears to be a complicated process.

[cwalter]

I just isoloated a nav switch tripping in flight and only in flight on my 1979 231. It was isolated to the dimmer circuit that appears to feed the annunciator panel for the purpose of dimming at least the gear down indicator during night ops. I have not investigated deeper yet but disconnected that wire from switch and all seems well.

There are 4 wires on the switch connected by 2 terminal lugs (2 wires each). You can first isolate the pair that runs 2 of the lights, in mine it was left wing and tail on one. Next you can use a fine needle like a sewing needle to pierce the insulation on the other set to find the right wing. The remaining wire is the dimmer wire. Piercing with fine needle will not damage or expose wire.

I also had a landing light trip in flight as well a while back. Not sure your light configuartion but mine is on the nose cowl below the prop. Turns out exposed wire on the scat tubing directly adjacent to the exposed terminals on the landing light was shorting during flight.The scat tubing runs under the engine and detached from a engine mount cross member.

Chris

[bgpilot1]

I had the same issue in my 67 M20F.  I got a new switch for the Nav and the problem went away.  Could it be as simple as that?

Barry

[cwalter]

Very well could be. I figured I would do some troubleshotting before spending $160 without knowing that was the issue.

Chris

[AustinChurch]

When I owned a '67 "C", I had the same issue on my landing lights.  The landing light switch would actually trip and flip off after approximately 1 minute.  I would then have to hold the toggle switch in the on position to keep the lights on.  I replaced said switch and that fixed the problem.  Being mechanical, they do wear out.

[cwalter]

You raise another good troubleshooting point. In my case you could not hold the switch - it was actually a short that was causing the trip. At least in the 231 the switch is also the breaker. It was enough of a voltage disruption to disrupted the auotpilot when engaged. That symptom still could have been the switch. In a 30 year old plane the contacts can get resistive!

[Hank]

My gear light decided to not stay on, resetting itself periodically one night. Twice it reset my COM@ King radio to 120.00 when it went out, and then on base to land, it reset my 430! Turned out to be cracked insulation on the landing light wire intermittently grounding out on the cowl, a quick and cheap fix.