Voltage Regulator Grimmlin

ARFlyer

ARFlyer

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ARFlyer
So we’ve gone through 3 voltage regulators in less then 200 hours in our 172N.

We’ve checked all the voltages and connections and have found nothing abnormal. Only abnormal item is our amp gauge on the JPI has always been +/- 10 amps randomly with the engine running. Could that be frying the regulator or is there another larger issue?
 
Check the wire that runs out of the alternator circuit breaker and feeds your main buss. We had one that was avionics cycling on and off. Looked under the dash and the insulation had melted off the wire. They had a STC higher amp alternator and replaced all the wires with a bigger gauge except that one
 
ARFlyer said:
Myself, my A&P, and his partner.
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Do you still have the original Cessna alternator/regulator or is it a different 3rd party system? What troubleshooting chart(s) did your AP use: Cessna, 3rd party, or ? The common reasons one might see multiple regulator failures is an internal alternator issue like mentioned by Dan T in previous threads or a wire issue that grounds a regulator wire even if its momentary. However, if following a standard T/S tree those issues usually are found. Regardless, with the system indicating a 20 amp swing I definitely wouldn't put another regulator on it until some more checks are done. Once I see where you are at on the T/S route might be able to recommend a few more things.
 
Some of the hybrid regulators (combination of mechanical relay and electronic voltage control) didn't like the alternator being switched off and on when under load. Don't do that in the runup to check the alternator with everything turned on. Just look at the ammeter. The alternator rotor's field winding generates a sharp voltage spike when it is shut off. Voltage spikes are deadly to equipment not designed to shunt them.

If your airplane has an ACU, it can be tricked into shutting down when the PTT switch is keyed. RF escaping from corroded antenna coax connections will do that by generating spurious high voltages in the ACU's sense line, triggering its overvolt function.
 
I think theoretically there is also a considerable NEGATIVE voltage spike generated on any devices including a solid state regulator, that are not seeing the battery as a ballast. For example, if alternator is generating a substantial current when the battery somehow disconnected including via a popped output circuit breaker. As a minimum electronics should be disconnected before any shutdowns.

Maybe someone can confirm?
 
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