Alternator problem?!

[chris_01]

Hi There,
yesterday, I experienced something strange.

I did the following:
- sat int the plane to do some avionics checks on ground before flight
- switched on the doubleswitch (master/alt)
- turned on avionics to play with the EDM on ground
- EDM showed me 12.0V on the battery - so fine, monitored this during playing for around 10 minutes.

- After these 10min, I tuned off Avionics bus (left on the red doubleswitch), primed, cranked up the engine.
- all good so far - didn't check much on the voltage as it still managed to run the starter sufficiently

I took off in the usual way. After initial climb, I got a voltage warning on the EDM 830 showing 11.8V. I turned off the landing light and nav lights and it went back to 12V.

Got some altitude, 12V were kind of stable. Turning off Alt for 2 seconds, turning on again - two cycles like this. -> No change in voltage and/or amp-meter. BTW - the amp meter was slightly left of middle. It went more left of middle when I tuned on the lights and EDM then alerted again 11.8V.
Whatever - It didn't go down below 11.7V in total. When most stuff was turned off, it was stable at 12V. Flew an hour and landed back home.

Now - what was this?? Usually when I fly, I have voltage readings about 13.5V or so on the EDM and Amperemeter in the middle. Didn't have time to let things cool down and make it from fresh and not waiting 10-15min between turn on the red switches and the actual start of the engine. Might try it out in a week time or so.

Does anyone have an idea what could be the reason? What should I check? Have I made a mistake?
Any idea welcome..
Thanks a lot & Stay Healthy,
Chris

[andy]

I don't think you mentioned whether or not your alternator warning light (low voltage light) was on. Check the connection from the inline fuse holder between the alternator control unit and the field post on the alternator. Some of us have had the wire from the fuse holder break at the lug on the alternator due to vibration fatigue over time. If no current is flowing through the alternator field, the alternator won't produce any output voltage and you'll be running off the battery. It makes sense that the ammeter would show a discharge in flight that would decrease when you switch off the heavy load items. I don't know if you have an alternator warning light or if it's working. Normally, the alternator warning light would come on when this happens. Recycling the alternator switch won't solve this problem.

[chris_01]

Thanks for the hint, Andy!
I'll check next time I get to the airport.
you mention the Alt warning light - upon purchase, they told me that they had covered that light already since years because it was always on. I didn't think much about it and used the amp-meter instead and now after installation also the EDM830 - which should be sufficient. Reading up the forum about these topics, I see that also others had a similar topic with that light and just disabled it.

Maybe the light was correct and announced some 'proper' malfunction. I'll only know once I have to time to troubleshoot again.
I'll keep you posted. Thanks!

[chris_01]

just to close the topic...
There was a loose cable crimp at the field current cable going to the charge controller. Fixed it, all good now!

off topic - but just to ask before I order the stuff.
I'm planning to change the oil next week. Currently, there is a Tempest AA48110-2 oil filter installed. I still have 3 Champion CH48110-1 around. Is it true that they are interchangeable and I don't need to order the -2 from Tempest?

Further - is it OK to re-use the existing gasket at the oil screen (GASKET, 1.00 I.D. x 1-1/4 O.D. x 3/32 annular - 06E19769-1.00) of the O360 C4F or do I have to put a new new one?