Overcharging problem

[Jim Smith]

Thanks Herb. I have seen other comments regarding a similar problem and it related to resistance on the field wires. Since it's a parallel system, I'm going to assume since it occurs with each alternator individually or both at the same time it must be at some point after where the field wires connect jointly. Thoughts?

[hharney]

It will depend on which alternator is taking the load, assuming it is not paralleling. It could be either one or both. Start by inspecting the field wires for any suspect connections. Compare resistance on each regulator and determine if it is one. If both are the same it could also be in the control board (I think your model has this).

[B2C2]

Hi Jim

I did an experiment yesterday where I took the battery off the charger for two days then started up the plane. All of the symptoms went away, indicating that in my case it is an effect of a fully charged battery being close to the regulator output voltage. This is consistent with it not showing up with my old beat up battery. I don't think this is much to worry about as it doesn't exceed 30V by much and fixes itself after a few minutes of running even for a fresh off the charger battery. I should mention that in addition to the new regulators and rebuilt alternator, I went through the field wiring with a meter and found that under some circumstances I could see high resistance through the alternator switch when I actuated it repeatedly. so I replaced it. Also there is a jumper lead that goes across that switch to give the regulator access to both alternators. Take a look at this as mine was heavily oxidized (black) and so I replaced it with fresh crimps. Check all the crimps associated with the field wiring for good measure. Also check the connections to the lugs attached to the field terminal on the alternator. My front alternator field lead had one strand left from lots of vibration.

Ben

[Jim Smith]

Ben that sounds like a lot of great things to check and will go through each of those items. Also my battery was pretty much shot and have replaced it but not had a chance to fly and test yet. That could very well be the source.