Main 50 amp Circuit Breaker Poppig

[JWE]

Shortly after we bought our aircraft the main 50 am circuit breaker started popping. 60 amp alternator with an external voltage regulator. We thought maybe the CB was bad so replaced it. Several flights with no issues then the CB popped again. We installed a CGR 30. Voltage read rock steady at 14.4, but amps were jumping erratically no matter what the electrical load. I/A checked and tightened several electrical connectors and the erratic amperage fluctuations reduced a bit but continued. CB continued to pop. Took it back to I/A last week. He checked the OHMs on the alternator and said they were out of tolerance. He replaced the alternator. We picked the airplane up yesterday from the shop and have only flown about 45 minutes since. The CB hasn't popped (yet - fingers crossed), but the amps continue to fluctuate although not nearly as much. With the new alternator the voltage reads steady at 14.2. It's my understanding he hooked the CGR 30 up so that the readings are from the alternator, not the battery. When the weather permits we'll fly some more and see if the CB pops again. In the meantime, any suggestions?

 

[wireweinie]

Something isn't right here. Check for any kind of short on the alternator output wires. All the way from the alternator, to the shunt, and on to the output circuit breaker. If there were problems with the regulator or field, the voltage should fluctuate with the current.

Web

 

[JWE]

Thanks, Web. We'll start checking the wires.

 

[DENNY]

Check all the terminal crimps by both pushing and pulling. I had a gremlin for two years that came and went. Turned out to be a crimped ring terminal. The wire would vibrate loose and move toward the ring and loose contact, when you would do the usual tug test it would reseat the wire and be good for 3-12 weeks before it would move again. Once I did a push pull test on everything it was easy to spot. DENNY

 

[JWE]

Denny, we'll check the crimps when we check the wiring. Thanks for the reply.

 

[wireweinie]

Let us know what you find.

Web

 

[JWE]

Will do.

 

[skywagon8a]

In addition to all of the above ...... what is your amperage consumption? You may be drawing at or more than 50 amps. Particularly if your battery is low on charge. (like after starting with an old battery) If your system is as I described and you have a piece of equipment which is intermittent such as flashing landing lights, that could answer your jumping amps question.

 

[JWE]

Skywagon8a, the max draw with everything on is around 30 amps, and that's with the taxi lights on which they almost never are. The landing lights are LED. Fairly new battery. Amps jump is continuous no matter how little or how much the draw and no matter which systems are on. I would expect some fluctuation with flashing lights, but the amperage jump is erratic not like you'd expect with a wig wag. At this point I'm leaning toward a short of some kind. Now we just need to find it.

 

[jrussl]

A friend had this exact same issue and found that his ground wire from the battery to the airframe was not rock solid. As I understand it, the battery acts as a shock absorber to the whole electrical system. If the connection to the battery is intermittent, the regulator can lose its reference and do some weird stuff. Check connections on both sides of the battery and and the ground wire to the airframe.


Sent from my iPad using SuperCub.Org

 

[BC12D-4-85]

Sometimes batteries can get bad and do weird things internally. Make sure yours is ok - maybe short swap to test just eliminate that as a source.

Gary

 

[JWE]

jrussl, I've checked all the connections in the battery area and found nothing obviously amiss.

BC12D-4-85, this was happening before the battery was swapped out for a new one.

 

[BC12D-4-85]

Is there any radio/intercom audio noise associated with the amp jumps? Maybe not similar but I rode with a fried in his PA-18 that would intermittently jump amps and make a brief tone audio interference breaking squelch. He took it in and they fixed it. Not sure what but I can ask when he's around. His ammeter (in a combination gauge) was initially wired in reverse (it showed - amps when charging) they found is all he said later.

Gary

 

[skywagon8a]

amps were jumping erratically no matter what the electrical load.

I just remembered another fix I was advised to do. Solder a capacitor across one of the relays in the regulator. I forget which one, but it solved the issue. Perhaps Web has the answer?

 

[frequent_flyer]

Not quite the same problem but I had an intermittent electrical fault on my PA-28 that I eventually traced to the main output lead of the alternator. It had chafed in a clamp, the clamp padding had worn through, and the alternator output was intermittently shorting to the engine.

Easy to fix but not so easy to find.

 

[akavidflyer]

sounds like an arcing wire to me.

 

[wireweinie]

I just remembered another fix I was advised to do. Solder a capacitor across one of the relays in the regulator. I forget which one, but it solved the issue. Perhaps Web has the answer?

This would work if the system was functioning normally and just had some noise. Or replace the reg with a solid state type.

The thing that catches my eye here, is the steady voltage but erratic current flow. I've seen this before when one of the rectifier diodes came loose from its mounting plate. But as the OP has already replaced the alternator I think that it is an intermittent short somewhere on the alternator output lead.

Web

 

[JWE]

Still checking, guys. Thanks for all the recommendations...

 

[BC12D-4-85]

Friend with the Cub in #13 replied they had to replace the voltage regulator to fix his radio noise and breaker going off line. Not necessarily the same source of problem of course.

Gary