Sweptline.ORG

hello,
i own a 1970 d200. we have just replaced the complete turn signal switch in the column with a nos mopar unit to fix the "one brake light" problem. both brake lights work great and my signals both work great. my new problem is that when i want to drive at night and i put the headlights on and press the brake pedal or signal right or left, the front and rear running lights short out, popping the fuse. the headlights themselves still work fine.
thanks a lot for the help!
james veltri
san marcos, california

James to the site , if you just replaced you T swetch & all this started , you eather have a wire crossed or a wire grounding out both the T signiles & brake lights are the same just go back & double check your work

All running lights are a differant system than the signal/brake lights
though they run to the same light buckets.
Got something plugged in wrong or cross wired that should not be.
Need to check all those green and yellow wires to make sure that
everything is were it belongs and make sure your power from the
light switch is using the right power feed.... and the one that
feeds the brake also.

Just had a thought, has this truck ever been wired for
a trailor??

the truck has the new style four prong trailer connector. i just am so frustrated by this . thanks for all of your comments and keep them coming!
james veltri
san marcos, ca

I was trying to think of were the running lights and signals
might be crossed and one of the more common places that
can happen would be at a the wiring at a trailer plug.
Only way to check this is to pull the plug out and remove all
the wires and check to see if it still pops the fuse.
For fuses to blow, you have to have a dead ground and for
it to happen with the brake/signals and the running lights
it needs to involve both, little odd for it to happen when
one system works ok till the other system is on.

I've been mulling this one over as well. It seems odd that both systems operate normally alone, but fuse blows when both operate. Fuse will blow for only one reason; overcurrent. This may be caused by "short" to ground, or by too high a load.
I'll try to find time to print out the diagram and hi-light the paths.

I'm having one of those days, but it makes for creative thinking. If they work good when only one system is on by itself, then there has to be a bridge between the two systems to short them out when one is connected. You turn the lights on and it completes one circuit and runs one feed to the tailights/turn indicators. If you hit the brakes or signal, it completes a different circuit that send a separate signal to the same lights. Could it be possible that one circuit is using the other for ground until that circuit is opened, at which time the fuse blows? If the only thing you changed is the turn signal switch, then it would have to have something to do with that. Could you have pinched a wire or possibly have a broken main connector that is combining circuits?.. I'm kinda just thinking out loud, but maybe it will spark someone that actually knows what they are talking about...