Destroy the Regulator?

hevansrv7a · #1 07-15-2007, 06:33 AM

"If you open the charging circuit while it is in operation, it will destroy the regulator."

The quote is from Van's web store.

Does this mean that if you turn off the alternator field circuit (in other words open it) while it is doing its job, it will destroy the regulator or does it refer to the output side?

I thought the purpose of a separate alternator switch or of one side of the classic Cessna big red switch was to be able to turn off the alternator if there was an over-voltage condition.

I ask because my alternator (Van's 60A) suddenly stopped working. I don't recall having turned it off while it was working, but I guess I could have. I only have 90 hours on the airplane, same on the alternator. It seems a little early for a sudden and complete failure. Yes, I've checked all the connections and taken it to an auto shop to "test".

I am knowledge-impaired in many areas and this one is near the top of the list. Experts welcome.

Walt · #2 07-15-2007, 06:54 AM

Don't open the output side (battery lead) while the alternator output is on, hence the normal switch shuts off the alternator first and then opens the bat relay.

airguy · #3 07-15-2007, 07:23 AM

Correct. Killing the field current is the proper way to shut down an alternator, and is regulator-friendly. Then open the battery (output).

Kevin Horton · #4 07-15-2007, 07:35 AM

Quote:

Originally Posted by hevansrv7a

I thought the purpose of a separate alternator switch or of one side of the classic Cessna big red switch was to be able to turn off the alternator if there was an over-voltage condition.

If you have a sustained overvoltage, the regulator has almost certainly already failed. So it doesn't matter if turning off the alternator during an overvoltage would destroy the alternator.

Turning the alternator off by stopping power to the field should cause no damage. Removing alternator power by opening its output circuit while it is charging the battery could cause a very high voltage internal to the alternator, and this could damage the regulator.

There seem to have been quite a few cases where the internally regulated alternators that Van sold have killed their regulators when the pilot selected the alternator OFF. I believe Van stopped selling the problematic alternators some time ago.

hevansrv7a · #5 07-15-2007, 08:10 AM

The three of you have educated me and I am now convinced I did not cause the problem. I'm not even sure I could have, since I have the Cessna master switch. There was no overvoltage in my case, just zero output.

For anyone lurking out there, I got these part numbers from this site:
Lester 14684
Beck-Arnley 186-0373
and I got this from the local parts store: Bosch 14824.

I hope this helps someone.

Thanks again.