Ignition ON->OFF blows fuse

[Jeff_S]

Helping a neighbor debug an electrical problem with his 2004 Signature 42 Chateau.

The Map Light fuse in the service bay keeps blowing. Turning on the Passenger Side ceiling lights would blow the fuse, and we definately found a short on the Pos. wire between the P/S switch and the ceiling lights. A new wire from the P/S arm rest to the ceiling will be needed, but for now we have isolated the P/S ceiling lights from everything else (it's not part of any circuit).

HERE IS THE BRAIN TEASER: Once we put a new fuse in the Map Light position in the Service Bay, other loads (driver's side ceiling lights, flexible map lights) all work. If the Ignition is turned on, everything is still working. Then, upon turning the Ignition OFF, the Map Light fuse blows.

This Map Light circuit should have no dependancy on the Ignition Switch position, much less cause repeated fuse failures when the Ignition Switch goes from ON to OFF. (Again, the grounded Pos wire on the P/S is no longer part of any circuit.)

Any hints would be appreciated.

Jeff S.

[nodine]

Quote:

Originally Posted by Jeff_S Helping a neighbor debug an electrical problem with his 2004 Signature 42 Chateau. The Map Light fuse in the service bay keeps blowing. Turning on the Passenger Side ceiling lights would blow the fuse, and we definately found a short on the Pos. wire between the P/S switch and the ceiling lights. A new wire from the P/S arm rest to the ceiling will be needed, but for now we have isolated the P/S ceiling lights from everything else (it's not part of any circuit). HERE IS THE BRAIN TEASER: Once we put a new fuse in the Map Light position in the Service Bay, other loads (driver's side ceiling lights, flexible map lights) all work. If the Ignition is turned on, everything is still working. Then, upon turning the Ignition OFF, the Map Light fuse blows. This Map Light circuit should have no dependancy on the Ignition Switch position, much less cause repeated fuse failures when the Ignition Switch goes from ON to OFF. (Again, the grounded Pos wire on the P/S is no longer part of any circuit.) Any hints would be appreciated. Jeff S.

I can't help much but since we are talking about an 04 Sig I bet it has the multiplex system that uses CANbus technologh to control lights and other components all over the coach. Could be that when the ignition is turned off that multiplex system is energizing something that it should not be. I believe the sponsor of this Monaco Owner Forum, Mega Tech of Oregon, produced that system for Monaco.

Bob

[Jeff_S]

Quote:

Originally Posted by nodine ... I bet it has the multiplex system that uses CANbus technology to control lights and other components all over the coach. Could be that when the ignition is turned off that multiplex system is energizing something that it should not be.

So that would be improper programming of the multiplexer. Probably a factory repair then, not little ol' me.

Is there some kind of "exit lighting" that is triggered when the ignition is shut off, and is on for say 1 minute?

That exit lighting fixture could have a short causing the Map Light fuse to blow when turning off the ignition. This coach is new to my neighbor. He knows blowing a fuse is wrong, and there has been something wrong with this circuit since he bought it.

[Jeff_S]

Quote:

Originally Posted by Jeff_S ... Is there some kind of "exit lighting" that is triggered when the ignition is shut off, and is on for say 1 minute?

ANSWER: YES.

Today via help from Monaco, we determined that a relay located in the front service bay (front run box) is providing +12V to the P/S ceiling light for 30 seconds after the ignition is turned off. That is the same wire that seems to be grounded because manual operation of the P/S ceiling lights would also blow the Map Light fuse.

Now the next step is to determine where the short is ocurring, or abandon the wire and completely replace it from the front service bay & P/S armrest to the ceiling above the entry door. (Actually finding the cause of the ground might avoid other problems in the future to nearby wires.)