Electrical Circuit Overheat?

[carolinaflying]

Curious for your thoughts since the mechanic is closed today. Last night I took my 68 M20C out for the first night flight. I wanted to be by myself since I've already found a number of things that need to be fixed in daylight hours! Everything pre-flighted fine and off I went. On my second approach to landing, all three of my light toggle switches simultaneously flipped off on short final. I was only on the yoke and throttle at the time. Safe landing and tried to pop the landing light back on the runway to no avail. During taxi back to tie down I was able to get all of the lights back on and they stayed on until shut down. My radios and transponder worked normal and the electric fuel pump worked fine as well. No over voltage light (but it's never illuminated so it could be burned out) and amps were fine once I was able to get light on the instrument. No popping, crackling, or electrical burning smell.

The flight lasted a total of 25 minutes from crank up to shut down. It was a warm summer evening but nothing ridiculous. As I research online and play the scenario back in my head, I'm almost wondering if the lights overheating would cause this problem? No circuit breakers blew but I understand these toggle switches act as a circuit breaker as well. The fact they would not switch back on immediately but did within a few minutes of failure prior to shutdown leads me to believe whatever that was too hot had cooled enough. If I had an overloaded circuit I imagine I would have experienced the issue sooner than 20 minutes, loose wire or ground would show intermittent issues instead of all 3 immediately shutting down?

I had left my landing light on the entire flight due to staying in the pattern. I had not been adjusting anything electrical after my run up, just power adjustments. Since my landing light is old school, my initial guess is it got too hot and blew my circuit but I am open to hearing your opinions as my electrical expertise usually involves shocking myself. Needless to say, no more night flights until this gremlin is fixed!

Thanks

[Yetti]

old weak breaker switches.  get an led landing light

 

[Yetti]

There is a bus behind the switches.  The panel may have shifted.   Can happen with old vibration mounts.  Put cell phone behind panel and take lots of pictures

[carusoam]

+1 on circuit breakers wearing out...

+1 on panel bolts/vibration dampers allowing sag...

how much space is there between the CB in The on position and the bottom of the plastic panel cover?

The world is moving towards LED landing lights.

Best regards,

-a-

[rakesb]

We fly a 1966 M20C. Four years ago, we had the generator cleaned and bench tested after the battery went dead. Brushes had 50% of useful life remaining. Continued to have partial and complete power losses and circuit breakers pop in flight. Finally, at annual two years ago, I asked Don Maxwell to install the PlanePower alternator conversion kit that I purchased at Airventure. Electrical problems solved!

[tony]

Your switches (Circuit breakers) are corroded inside from age and nonuse.  They just need to be replaced.  They are a bit pricey.  Google "Klixon 7270 Series Aircraft Circuit Breakers"

[Guitarmaster]

Ditto on the circuit Breakers. When they get old like that one will get hot and can trip the adjacent Breakers as well.
The fact that everything worked after you turn it back on, essentially giving it it cool down period, is a dead giveaway.

Sent from my XT1585 using Tapatalk

[Hank]

Had trouble keeping my landing light on one time, and it took the radios out with it the second and third times it tripped. . . Reset them to 120.0 in the pattern. Made a good no-light landing wearing my prescription sunglasses, since i had left my regular glasses in the car.    Turned out the landing light wire had chafed against the cowl and worn through the insulation. Fixed that and everything was OK. 

When that bulb finally blew, i went LED and have not looked back. But keeping it on does make my Nav 2 (KY97) hard to read . . .

[pinerunner]

On 8/20/2017 at 5:05 PM, Yetti said:

There is a bus behind the switches.  The panel may have shifted.   Can happen with old vibration mounts.  Put cell phone behind panel and take lots of pictures

My old E model kept turning off toggle switches until I got new vibration mounts installed at my first annual. The instrument panel was just drooping too much. I would think that if you were over loading one circuit that would be the only one to trip off. Maybe when you set up for landing you set up a harmonic with panel that makes it just barely knock the switches off. I'm just guessing but what Yetti said rang a bell with me.

[Yetti]

In other news Amazon has Wheelen led tractor light bulbs in PAR 46 or PAR 36