Bizzare Problem: Autopilot Only Works when Shore Power Is Plugged In

[Fishman_Tx]

Can you hear the Autopilot if it were to come on while you're in the engine compartment or bilge? Try disc shore power, turn on pilot, go fiddle/wiggle all your main ground points 1st. You might get lucky and hear it come on. Use the KISS method first and eliminate the easy points first before getting into the "nitty-gritty". Check main ground points and busbar for boat grounds. If thruhulls are the primary ground, check for an open loop with a meter. Don't use the "Continuity/Diode" function, this won't account for hi-res opens, use the ohms setting. Resistance levels should be near 0 across each leg. Start from the primary ground and work back to the busbar(if you have one). Test thru the connection points not "to" or "at" them.
Ex: Engine block as boat ground: place one lead ON the block on bare metal(unpainted) and test to the busbar itself(not the connection) unless your using bussing strips. You may need to add wire to your test lead to allow you to reach it(alligator clip or some other solid connection). Reading should be very near "0"....

[dana-tenacity]

Am I the only one who thought the title of this thread hilarious?

[Fishman_Tx]

sgtPluck?
Didi you ever figger out the problem? If, so....what was it?

[sgtPluck]

Not yet - I was called out to California for a few weeks of business. But will have a look when I get back and will update this thread if and when I figure it out

[Fishman_Tx]

Ok, Thx!

[sgtPluck]

For the record, this problem was fixed.
The problem was indeed a grounding one... the auto pilot's negative wire was connected to the AC ground.

D'oh!

Thx everyone for the suggestions!

[jkleins]

I guess that is why the ABYC is recommending using yellow wire for all DC ground wires and black for AC. I thought that was pretty dumb when I first heard it as I thought it was so unlikely to happen. Stupid me.

Jim

[cantxsailor]

I'm glad he got it fixed. It sounded like a exorcism was going to be needed. I had a similar electrical anomally years ago and feared I was going to have to call Ghost Busters. I could hear a pump running but when ever I looked it would quit running. It finally quit doing it but we never did find out why it did it in the first place.......m