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dwilson

Well Known Member
Flying Sunday from Santa Barbara to Portland. Great weather, smooth air.

Got an intermittent over voltage alarm on my GRT EIS and EFIS. Meter read up to 15.2 V on the main bus. (Dual batt, dual alt setup.)

I switched off the main alt and switched on the cross feed so that the B/U alt was carrying the whole load. Voltage went back to normal.

Flew like that for a few minutes then switched off the cross feed and switched the main alt back on.

Voltage slowly - over 15 min- went back up into the 15V range.

Repeated the cycle and the second time around the voltage remained in the normal range for the rest of the flight. (about 5 hours)

Where do I start looking for the problem?????

have B+C alternators and external regulators.

Thanks,
Duane
 
Connections

The regulator may be getting flaky but the first thing to check is all of the connections for clean and tight, particularly at the battery and the regulator's sense line. A problem there could cause the regulator to think that the system voltage was low (because of voltage drop in the sense circuit) and increase the alternator's output to compensate.

Don't forget to check the grounds, alternator and regulator. Voltage drops can occur there too. Make sure that your ground bonds are secure and tight.
 
Talk to B&C . . .

First check all connections to the regulator - especially the sense lead. If nothing is suspect there, B&C should be able to point you in the right direction.
 
I had that problem. It was my master switch (split cessna type). Replaced switch back to normal.
 
It could possibly be that the regulator has gotten out of adjustment. I have B&C and know that they are adjustable. Is the regulator behind the firewall as directed by B&C? That could be another problem area--too much heat on the reg.

Bob Kelly
 
Need to be sure it isn't a faulty indication - what did the voltage indicate immediately when you shut off the alternator?
 
Found a loose connection

I found the connection from the + side of the battery to the selenoid was loose at the selenoid end. I tightened it. Will put it back together and fly it and see what it does.

I don't think it was an instrumentation error because as soon as I turned of the offending alternator the voltage read normal.

Thanks for the suggestions.

Duane
 
normal

With the alternator off the voltage went to about 12.5. When the backup alternator was switched on it went up to about 14.2

I think those are normal?
 
Yes, normal readings.

You might want to look into overvoltage protection. It can get very expensive, if you don't and the voltage regulator fails again.
 
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