Navlights circuit breaking

[jbh-in-sc]

Hi All,
I think this is my first post, but I enjoy reading the info stored in this huge database.

I have an issue with my navlights (and hence, my ADS-B out). The breaker keeps breaking. I'm not sure how to troubleshoot this, since I'm not an A&P. My '59 PA-22-150 has the rheostat dimmer switch for navlights and ads-b (wingtip from uavionix). I haven't really figured out how long it takes to break, since I just noticed it on the last training flight, but I do know I haven't had any pings to Flightaware in the last 2 flights.

I assume possible causes are:
1- the switch
2- the wiring
3- the navlights fixture on the right wingtip.

It has just spent it's first week outside in years. I think that might be a contributing factor.

What can I do as a student pilot to troubleshoot this? My first idea is to remove the right bulb and see if it still breaks. I wish i could replace the rheostat with a couple toggles to check that, but I assume the faa would serve a no-knock on me if i did that.

Thanks in advance.

 

[jbh-in-sc]

Here’s the circuit breakers and the navlight rheostat

 

[PA-16]

Had tha same thang hapen tu me a few years ago, the current sum of all 3 position lights took its tole on the 30 year old 10amp circuit breaker, so I fixed it by replacing the hi amp incandesant nav light bulbs with LED bulbs https://www.aero-lites.com/product-page/aircraft-tailfin-navigation-light

 

[Steve Pierce]

Systematically remove a bulb from the system and see if the breaker quits popping. If it does then the breaker is overloaded. If it doesn't you have a short somewhere and will need to check each wire to ground. More than likely you have corrosion in one of your nav lights creating high resistance. Clean the light sockets and see if the problem persists.

 

[RRHall]

The old style nav lights pull quit a bit of amperage. With the ADSB it may be too much for the breaker. You can install a larger amp breaker, or get led nav light bulbs. Since you said the plane was outside maybe condensation, dew or rain got into the system and shorted it out. What size is the current breaker? Uavionix says the beacon only pulls about 0.25 amp. Nav lights can draw up to 2 amps per wing and one for the tail, are strobes on the same circuit? I don't see a separate CB for the strobes. A 5 amp CB can quickly get overloaded but I see you have a 10 amp one..

 

[SeanM]

I would start with a current measurement of the circuit while operating. Easy to do with any modern multimeter. With the breaker open, hook up your meter across the terminals of the breaker and turn on the lights on. If the static current is half of the rated breaker, then you probably have a momentary short that is tripping the breaker. If the current is close to the breaker limit, remove one bulb at a time, see if one is drawing excessive current. I would also look at the intensity of each bulb, a dull bulb indicates a wiring issue. Lastly, check the voltage at each component, it should be close to battery voltage with the bulb on. if it's a few volts less, then there is a voltage drop due to resistance. Resistance causes heat, which will draw more current....