DC short?

[hoagies_OTR]

Hello,

I'm having trouble getting my battery bank to energize the DC circuits. There is a 'workaround' toggle switch that bypasses a short somewhere in the rear of the coach that affects the rear marker/clearance lights, closing the switch controls the rear clearance lights for when we're in transit, it's open to bypass the short when not. I replaced this switch previously, the short was manifesting when you stepped on the rear bathroom floor, as it has gone bad. Replacing the switch did not alleviate the problem this time.

I can still energize the DC circuits from the tow vehicle and through shore power. Fuses appear to all be good. I'm not an electrician by any stretch of the imagination, but I have a multimeter and can follow direction. Is there somewhere I should start sticking my meter first? Any silly things I may be overlooking? Coach is a 1969 Ambassador. Thanks for any help!

[Rich W]

[QUOTE=hoagies_OTR;1870407]Hello,

There is a 'workaround' toggle switch that bypasses a short somewhere in the rear of the coach that affects the rear marker/clearance lights, closing the switch controls the rear clearance lights for when we're in transit, it's open to bypass the short when not. /QUOTE]

So if the switch is closed and someone steps on the bathroom floor it shorts out and blows a fuse? If the switch wires go to the rear marker lights, it shouldn't be powered unless the TV is hooked up. Correct?

So the short is in a line that comes from the umbilical, passes under the bathroom floor and goes to the rear markers. Some PO has added a switch to that wire to open it, but if the TV isn't hooked up, why is it energized?

Have you taken voltage readings on each side of the switch? (multimeter to ground somewhere, then red probe to each side of the switch.) TV and umbilical hooked up and lights on, then readings with the umbilical disconnected.

Run a continuity check between each side and the ground. Have someone step on the bathroom floor to see if that's still going to ground. You may have burned through the wire so there's no voltage going to your switch any longer.

It would be best to find the short and fix it. If it occurs when you step on the floor it's probably a pinched wire underneath. You're going to have to pull up the floor to get at it, or maybe drop / cut into the belly pan underneath.

Where is the switch and were are the wires coming from?
Take some readings and post the results.

[sgschwend]

Perhaps a tracer could find the path of the wire near where the signal goes away will be the short. Find it and fix it, much better than the risk of a fire.