What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Alternator noise

s24789

s24789

Well Known Member
Patron
Just recently on startup we hear a whine that is rpm dependent that normally goes away after 10 or 15 minutes. Turning off the alternator kills the whine. Just started doing this in the last 30 hours and we have 210 hours on the plane. Any thoughts from the experts ?
Thanks in advance
Phelps
 
Do you hear the whine in the intercom /headsets or is it a sound you hear that is mechanically generated?
 
Thanks Walt. The weird thing is that it goes away after 15 minutes or so. Also is this something I can fix or is it a remove and send to plane power.

Phelps
 
I have a similar issue and in my case the whine is related to how much current my alternator is producing. After a start, the alternator generates more current than normal getting the battery charged back up. I have an ammeter installed that measures current going into and out of my battery, and the whine volume is proportional to the amount of charge going into the battery. Also, if I turn on additional loads, landing lights, etc. right after a start I notice an increase in the whine volume. As my battery got older it took more current and longer to charge back up after a start and the whine became more noticeable. Because my battery was 7 years old and getting a bit weak I decided to replace it before it let me down. Now with the new battery the whine is much less noticeable and only lasts a couple minutes after a start.
 
Thanks for info Joe. We also noted this first occurred or was noticed after a night flight some months ago. We will continue to watch it.
Phelps
 
s24789 said:
Thanks Walt. The weird thing is that it goes away after 15 minutes or so. Also is this something I can fix or is it a remove and send to plane power.

Phelps
Click to expand...

The diode pack is not user replaceable, send it back to PP and let them check it, they are good folks and stand behind their stuff.
 
The reason that the noise appears to go away is that the battery is now basically charged up. Pull on the landing lights and the whine will come back. The whine is actually there all the time now it is just at a very low level and you can't here it. As others have said the problem is most likely a bad diode.
 
Spent twenty minutes on the phone with Dick from Plane Power today trying to lead him to say my alternator was causing the noise in my headsets after startup and intermittently in flight. He gave me some things to try and I am fairly convinced now that the Garmin 496 may be the culprit.

It happened about six times tonight and pulling the circuit breaker and waiting for the unit to power down (30 secs) and the noise went away. Pushing the breaker back in and the noise would reappear. Will start delving into the GPS wiring next. Kudos to Dick for,spending the time with a fellow RVer.
Phelps
 
Walt said:
Most likely one of the alternator diodes has failed.
Click to expand...

On doing my annual, I found a broken wire at the alternator. It turned out to be just a wire shield. So I fixed it. Now, I get get noise from my landing light alternator circuit. Funny, no noise before I fixed that broken shield.
Now, today the alternator quit. should I take off the shield?
 
The shield should be grounded at one end, not both. If it is grounded behind the panel, you don't want it grounded at the alternator.
 
You must log in or register to reply here.
Back
Top