Shadrach Posted October 6, 2015 Report Posted October 6, 2015 I have an odd issue with my nav lights. The Klixon Breaker/toggle switch pops inside of 15 minutes of departure. If a reach underneath the switch panel and touch the switch after it has popped, it is very warm to the touch. What's odd about it is that I can not duplicate it on the ground with just the battery. I left the nav light on for about 45min (battery power only) after landing...no issue. I readily admit that electronics are not my strongest subject. Is there anyone here with a stronger rasp hat might be able to help? This started right after annual. Thanks! Quote
Hank Posted October 6, 2015 Report Posted October 6, 2015 What breakers are right beside it, running in the air that weren't turned on in your ground test? You could simply be picking up heat from the next switch over and tripping the small Nav Light breaker Quote
Shadrach Posted October 6, 2015 Author Report Posted October 6, 2015 (edited) The rotating beacon is on one side and the landing light is on the other. That's smart thinking, but I ran it solo in the air and it still pops... Edited October 6, 2015 by Shadrach Quote
Mooneymite Posted October 6, 2015 Report Posted October 6, 2015 Based on doing the easy things first, check for/clean corrosion on the nav bulbs and in the bulb sockets. Quote
Jerry 5TJ Posted October 6, 2015 Report Posted October 6, 2015 (edited) Increased resistance in the bulb or socket won't cause this: That would reduce heat in the breaker. Increased resistance inside the Klixon circuit breaker will increase heat as you've seen. Dont forget your ground test with battery is different than airborne in two ways - vibration and higher bus voltage. Check all the cheap stuff then buy a replacement Klixon. That's where the trouble lies, most likely. Edited October 6, 2015 by jerry-N5911Q Quote
N201MKTurbo Posted October 6, 2015 Report Posted October 6, 2015 Ideally, you should do a current measurement. It is the only way to determine if it is the breaker or something else. Most handheld meters will measure up to 10 amps, I don't recall what the rating of that breaker is. If it is more then 10 amps it is more difficult. To do the current measurement you will need to remove the non-bussbar lead from the breaker, connect one lead from the meter to the breaker and the other to the lead you removed. make sure to connect the red meter lead to the 10 amp connection on the meter. Turn on the nav lights and read the current. Start the engine and run it up and read the current. if it is lower then the breaker rating then it is the breaker that is bad. If it is higher then the breaker rating then it is something else. 1 Quote
N201MKTurbo Posted October 6, 2015 Report Posted October 6, 2015 (edited) If this test shows the breaker is bad, it may be cheaper to switch to LED lights then to replace the breaker. Edited October 6, 2015 by N201MKTurbo Quote
Shadrach Posted October 6, 2015 Author Report Posted October 6, 2015 One other variable I forgot to mention. My system is a 12V system. The rear nav light was replaced with a 28v bulb at some point. I don't know when or who did it. We buy multiple bulbs at a time and all of the extras we have 12s so I'm thinking the 28V bulb was packaged as a 12V. Anyway, my MX noticed the tail light was dim and that's how we discovered the 28. I was replaced it with a 12V. Quote
N201MKTurbo Posted October 6, 2015 Report Posted October 6, 2015 Maybe the 28 V bulb was put in to mitigate the weak breaker. 1 Quote
Shadrach Posted October 6, 2015 Author Report Posted October 6, 2015 Maybe the 28 V bulb was put in to mitigate the weak breaker. Tis' possible with 3 folks flying it that someone did that. Do you have an LED bulb that you'd recommend? Quote
N201MKTurbo Posted October 6, 2015 Report Posted October 6, 2015 No, I still have incandescent bulbs and will until they cause problems. Quote
carusoam Posted October 6, 2015 Report Posted October 6, 2015 Additional data point.... The landing light breaker fails this way with a more common frequency. The way to tell the breaker is wearing can be as simple as the the feel when you turn it on. If it barely clicks into the on position vs. snapping into place like the other good ones it has the same light touch to turn itself off. The mechanical resistance seems to change with age and or use. Also check if something is lightly bumping the switch. When the instrument panel bumps around in flight, it would turn off my C's landing light. New shock mounts cured that issue. My landing light switch had a plastic sleeve added to help identify it. It would get bumped before the others... Best regards, -a- Quote
geoffb Posted October 6, 2015 Report Posted October 6, 2015 Breaker is getting old. The reason it trips in flight is because on battery power the system is running at 11.8-ish volts (depending on total load) and with the generator on line the system is probably running at 13.5-14.0 volts so the nav light circuit is getting 15-20% more current with the engine running. Quote
carusoam Posted October 6, 2015 Report Posted October 6, 2015 (edited) Ross, Do you have an IR thermometer? Check the temp of the breaker running on the ground, based on battery voltage. Check the temp of the breaker when it trips, based on alternator voltage. A worn circuit breaker increases it's resistance. The ohms may be measurable(?) and the power used P=IV or I2R is increased in the switch. It may be easier to swap out the switch/CB...price and removing the buss bar may be challenges... I would also expect that a worn or pinched wire could be shorting in the tail section. They get tugged a bit when cleaning the annual bird's nest out and things like that... best regards and thanks for the memory boost, -a- Edited October 6, 2015 by carusoam 1 Quote
Shadrach Posted October 6, 2015 Author Report Posted October 6, 2015 Breaker is getting old. The reason it trips in flight is because on battery power the system is running at 11.8-ish volts (depending on total load) and with the generator on line the system is probably running at 13.5-14.0 volts so the nav light circuit is getting 15-20% more current with the engine running. It's not getting old, it is old...as in 47year old OE. You may be right that it's just age. However, I'm not sure that I buy that an additional 3.5 volts is killing it. Quote
N601RX Posted October 6, 2015 Report Posted October 6, 2015 It's either a weak breaker or corrosion on the busbar/terminal. It's marginal and the extra current due to the higher voltage is pushing it over the edge after several minutes. Any kind of short and it would pop immediately. Spruce is proud of these. 1 Quote
carusoam Posted October 6, 2015 Report Posted October 6, 2015 The extra voltage will generate extra heat. The CB operates on heat. It gets warm and springs open... When it wears, it springs at a lower temperature. Best regards, -a- 1 Quote
ArtVandelay Posted October 6, 2015 Report Posted October 6, 2015 I've had a brand new CB go bad, so it's not just old ones. Quote
Mooneymite Posted October 6, 2015 Report Posted October 6, 2015 (edited) I've had a brand new CB go bad, so it's not just old ones. There's nothing new about CB's. Those rascals have been around for years! Oh.....you're talking about Circuit Breakers..... Sorry. Edited October 6, 2015 by Mooneymite 2 Quote
RLCarter Posted October 7, 2015 Report Posted October 7, 2015 Check the resistance across the terminals of the Circuit Breaker, if the resistance is more than a couple of OHM's the CB is not making a good contact internally. High resistance is HEAT, CB's have a bi-metal spring which causes the Breaker to trip 1 Quote
Shadrach Posted October 7, 2015 Author Report Posted October 7, 2015 Check the resistance across the terminals of the Circuit Breaker, if the resistance is more than a couple of OHM's the CB is not making a good contact internally. High resistance is HEAT, CB's have a bi-metal spring which causes the Breaker to trip Can they be serviced? Quote
N201MKTurbo Posted October 7, 2015 Report Posted October 7, 2015 Not really. If it was after the Armageddon and it was the last CB on earth, I would disassemble it and make it work again. But short of that , no. 1 Quote
N601RX Posted October 7, 2015 Report Posted October 7, 2015 I've had a few of the originals go out. Ocasionally you see NOS or a newer model plane on ebay being parted out. I saw someone on ebay parting out a newer model plane a few years ago and sent him a message asking about all the CB. I got all of them for $100, it came out to about $3 each and I replaced all of mine and still have a few spares if I ever need them. 1 Quote
DrBill Posted October 8, 2015 Report Posted October 8, 2015 Measure the current to be sure you don't have a partial short somewhere. Should be about 3A for a 5A breaker (1A per bulb). Bill 1 Quote
Shadrach Posted October 8, 2015 Author Report Posted October 8, 2015 (edited) Ross, Do you have an IR thermometer? Check the temp of the breaker running on the ground, based on battery voltage. Check the temp of the breaker when it trips, based on alternator voltage. A worn circuit breaker increases it's resistance. The ohms may be measurable(?) and the power used P=IV or I2R is increased in the switch. It may be easier to swap out the switch/CB...price and removing the buss bar may be challenges... I would also expect that a worn or pinched wire could be shorting in the tail section. They get tugged a bit when cleaning the annual bird's nest out and things like that... best regards and thanks for the memory boost, -a- IR thermo showed consistent temps with it shut down. I'll try it running when I button it up tomorrow. Oddly the pax side nav light is almost 100df hotter than the other 2. Edited October 8, 2015 by Shadrach Quote
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