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  #1  
Unread 07-20-20, 09:51 PM
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Jhogan0101 Jhogan0101 is offline
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Help troubleshooting gen field breaker 337B

The gen field breaker is popping once every 30 mins or so when flying.
Trying to get to the bottom of it before going flying again. Also the landing light breaker is popping same interval.

What are the steps to trouble shoot this problem?
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  #2  
Unread 07-21-20, 05:42 AM
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Thumbs up Help troubleshooting gen field breaker 337B

Jhogan0101. Had the same problem. Thought it was my Voltage Regulator, so changed one to a ACU (alternator Control Unit). NOT.
Comes down to adding a 8 gauge wire from rear starter to front starter then to battery ground. I know this sounds strange but I was told, by Dr. Dave, electrical engineer, that the resistance in the airframe, from loose joints and corrosion, needs the extra ground wire and believe it or not that works. Now alternators are producing the correct voltage to the buss which allow for the heavier load of the landing lights. One other thing you might need to do is adjust the voltage regulator output voltage from (Book number) 27.7 volts to 28.7. As Dr. Dave explains it the new battery manufacturers are requiring higher voltages for charging their batteries. Hope this helps.
Regards, BILLS

Last edited by cessnadriver : 07-21-20 at 05:44 AM.
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Unread 07-21-20, 11:42 AM
JAG JAG is offline
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Popped breaker

I would trouble shoot with the easiest first.

Disconnect the wires at both ends and check the resistance of the wire. Given that the trip seems to be time bound, it is probably not a short to ground, but could be high resistance in the wire. If resistance is low (< 0.3 ohm), then that is good. I would go ahead and crimp new connections on both anyway, eliminating any chances of corrosion or poor connection. Don't forget to check the screws are tight at all the connectors as well (breaker to switch, switch to component and component to ground).

Next step would be to change (or swap) the breakers, to see if you have a weak breaker. Easier to just replace the breaker with a new one, considering these breakers have likely done years of service.

Bill mentioned upgrading the ground wires for the electrical system - this is an excellent upgrade (I have done this as well per Dr. Dave's suggestions) that may help.

I always view a breaker popping as telling me something is hot - and the breaker pops before you let the smoke out of the wire. Wires heat up due to excess resistance (poor connections, broken strands) or excess flow of power (short to ground, incorrect wire size, too much draw). Make sure your wire is sized right for the item your are running: has the Alternator been upgraded, is the landing light the right one, etc.

Jeff
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Unread 07-24-20, 09:44 PM
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Jhogan0101 Jhogan0101 is offline
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Thank you everyone. Also a huge thanks to Dr Dave for spending some time on the phone with me today troubleshooting.
Findings:

-#2 Voltage regulator was bad (zeftronics was ordered and will be primary it is replacing regulator installed in 1980, current 2 year old lamar will become backup)
-Wire from field gen breaker to master switch (K-PB10) needed to be replaced wire/connector became stressed from years of circuit breaker panel removal.
-5 amp field gen breaker was replaced, it was original.
-landing & taxi lights were replaced with led https://www.aero-lites.com/products

Some testing was done with a multimeter, so far everything looks good. Im going to do some more testing this weekend for voltage drops on other parts of the field gen circuit.

Hoping to fly it tomorrow, also hoping gen field breaker doesnt trip again.
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