A185F - charging system gremlin.

[Steve's Aircraft (Brian)]

Customer aircraft. Hoping someone here might of had the same issue and know the “fix”

1979 model with 24 volt system.

Here is what it’s doing:

Intermittently the alternator will go “off line” either right after take off and also during flight. Flight my customer did from Idaho to my shop if went off one time. Cycled the field switch and it came right back on. Previous flight he said it did it three times

Has new battery, new alternator, new Lamar voltage regulator. I have checked the wiring to the switch and breakers and find nothing wrong. All tight and no visible burnt crimp ends.

Flight home it went off once.

We are at a loss..

—Brian

[Gordon Misch]

I had overvoltage issues that were resolved by Web's suggestion to run an independent ground wire from alternator to ground buss. Maybe a possibility?????

[stewartb]

My 180 had a similar condition for about three years. Several experts and lots of hours chasing a problem I couldn’t recreate reliably. When I stripped my interior my mechanic friend re-wired the airplane from spinner to tail and installed a B&C alternator. I’ve never had a problem since. I figure there was a broken wire or cracked insulation somewhere.

[akmarty]

Any engine monitor data to look at?


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[Steve Pierce]

Many years ago I had a customer with a new Piper Saratoga that the alternator would shut down in flight. He would turn it off for a while and then it would start working again. He got mad and wanted me to replace everything. The alternator was $2400 in 1998 money all because it was clock different than the same thing for $100s. After going over the wiring schematic several times I determined the over voltage relay was about the only thing that could be doing this. I replaced it and no more issues. These intermittent problems can make you want to pull your hair out. I know that is not an option for you.

[LMartin]

Same on a 185F last year, and then lost the alternator that only had about 25 hours on it. At the advise of many, and a wiring harness with all new switches and breakers sent from Web to us in Michigan, and a new alternator and regulator….there have been no more problems.


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[SuperCub MD]

Had the same issue. Found the original Cessna main breaker would intermittently open without actually popping. Try a different breaker.

[wireweinie]

Check your master switch with an ohm meter. See if the continuity varies when you wiggle the switch. Then check the field and output breakers for any measurable resistance. Just to verify; these symptoms were present before the alternator was changed?

Web

[Steve's Aircraft (Brian)]

Check your master switch with an ohm meter. See if the continuity varies when you wiggle the switch. Then check the field and output breakers for any measurable resistance. Just to verify; these symptoms were present before the alternator was changed?

Web

Yes.. changed the alternator and regulator trying to solve the problem. Will have to double check the switch and breakers. This bird has the double Plastic Cessna switch in it. Has good grounds from engine and alternator.

—Brian

[Cub Builder]

I think Steve Pierce nailed it. Resetting the field also resets your over voltage protection. In all likelihood, the over voltage is getting triggered and taking the regulator down, either due to actual over voltage spikes or due to a failing overvoltage sense value, and that is shutting down the field until you cycle it. If you have a separate over voltage relay, you can either disable or replace it. If your overvoltage is integral to the regulator, then it becomes a regulator problem.

-Cub Builder

[BC12D-4-85]

I experienced similar events in a C-185---OV relay tripping. The A&P that examined it also found a bad diode in the alternator that was intermittently allowing AC into the system. The alternator would slowly get loud could be heard on both the com radios and radio tracking receiver. Fixed by replacing parts but it happened more than once. Another suspected a bouncing alternator belt was causing problems....pulleys and belt worn.

Gary

[beezerboy]

my vote would be to replace the breaker first