Electrical Issue

[Clarkie]

Ok. Here's one that is stumping us. New panel in the -6. Had some battery/alternator issues that have been resolved.

Yesterday, my buddy went to fly the airplane after it sat for a day and half and the battery was dead. No, the master wasn't left on, but what he found with the master off, he could throw other switches such as lights and they would power up. Not good. Installed freshly charged battery this morning to troubleshoot and we had the same issue. We figured the master relay or master switch itself was bad or some sort of bad wiring. Fast forward a few hours, he flew the airplane to the installer and when he went to demonstrate the problem, he could not replicate the problem. Ops check good as they say. Anyone have any ideas what the deal is here? We are still replacing the master relay and checking all connections.

[rv9av8tr]

I have seen on occasion that my master doesn't kill the buss until the engine is stopped. Only happens once in awhile, and it always drops off once the engine is down. I've assumed the Master Solenoid is hanging up for whatever reason, but haven't changed it out yet. Just another data point for a similar observation.

[SteinAir]

Do you have an independent backup battery in this plane (like an IBBS) or something similar? Also any "hot battery leads" that don't go through the master relay? Both of those things if not done correctly right can be vampires on your battery. Aside from the master relay not functioning properly (which should be very easy to figure out - and also very rare), there must be another 'leak' in your system somewhere.....

Cheers,
Stein

[Jesse]

How is he battery connected to the bus? It should be battery + directly to the master solenoid and then everything else on the other side of the master solenoid. Also, the master solenoid should use a ground connection to complete the circuit. When you flip the master Switch, do you hear it click? Check voltage on the bus side of the solenoid with the master switch off and it should read nothing.

Do you have a diode on the master solenoid? Is it installed correctly?

Was the engine running? As rv9av8tr said, sometimes the alternator will power the bus even without the battery connected. This is not a good thing. Never try that.

My guess is that there is some kind of E-bus setup that bypasses the master solenoid and that was not disconnected or turned off. If the master solenoid is, in fact, bad, then this would cause what you are seeing. Just the alt field will draw 3-5 amps even with the engine not running, which will drain your battery overnight.

[Clarkie]

There is an independent battery back up and a hot battery lead wired directly to a 12V "cig lighter." I do hear the "thump" when turning the master on. The engine was not running.

[Jesse]

What is the backup battery wired to? Disconnect it and the hot lead and see if this fixes it. If so, the. You can ring out those 2 items and find your problem. Assuming the solenoid isn't bad, which is rare, as Stein said.