Electrical Problem

[APM]

I've just joined the forum. I live in New Jersey and own a 3000 MK1 BT7 which is in running order but certainly not concours condition. I like to work on it but am not an expert.

I posted the the following problem on the introductory board and was advised to open it up to the wisdom and experience of the group.

I recently ran into a problem: I switched on the headlights and was met with a burning smell and smoke from under the dash - I quickly turned off! On inspection I find that the red wire going into the headlight switch on the dash has burned out (melted insulation). I'm concerned that this goes into the harness but everything else still seems to run fine! What are my options? Any advice would be much appreciated, many thanks.

 

[GregW]

That red wire actually comes out of the switch (at least the flow does :cz). That wire goes in a couple directions. One is to the panel light switch. The other direction is to the running/ turn signal lights at the four corners of the car. I would start at the bulbs and look for faults and frayed wires back towards the dash. Hopefully it will be obvious, might need to run a new red wire though.

 

[APM]

Thanks GregW, that actually gives me some encouragement, I'll take a look to see if I can pin point it. I'm hoping that I don't have to replace the whole harness.

 

[Ed_K]

I think it also feeds the license plate light who's wire has a habit of shorting out to the edge of the hole in the shroud.
But I don't have the diagram available now as I am still at work.

 

[Patrick67BJ8]

Thanks GregW, that actually gives me some encouragement, I'll take a look to see if I can pin point it. I'm hoping that I don't have to replace the whole harness.

And I bet the fuse didn't blow either!! Sometimes I wonder if the red wire was meant to be the fuse. I've never had a fuse blow in my Healey since 1971, but I'm on my second harness. Most of the time the "short" in the wiring is not enough to blow the fuse, but the red wire(located in the center of the bundle), will heat up enough and slightly melt but not enough to smoke. A "smoke" is more than likely a hard direct short. I have trouble shot the Healeys best with a ohm meter by completely unplugging all the circuits first and then checking them that way. You will have to remove the bulbs to check the lighting cicuits and my guess from expeience is you'll find the problem in one of the "lighting circuits".

Take the wiring diagram and have it enlarged by a graphics place to about 24" x 30" or more and then you can mark off every wire and circuit you've checked. Laminate it and use a grease pencil and it'll last you several years.
Patrick

 

[GregW]

And I bet the fuse didn't blow either!! Sometimes I wonder if the red wire was meant to be the fuse. I've never had a fuse blow in my Healey since 1971, but I'm on my second harness.

Yeah Patrick, I've been given a hard time in the past for having 14 some odd fuses (most are smaller ratings).

 

[APM]

Thanks guys, you're absolutely right the fuse didn't blow. I'll check out the numberplate wire for the short. I like the idea of blowing up and laminating the wiring diagram. Thanks for all the good advice and help.

 

[JodyFKerr]

[side topic]

I made a modification in my garage a few years back that's been invaluable. I turned my garage door into a giant whiteboard. (bonus side effect of insulating said door).

What's cool about it.
A) you can make notes/diagrams on it.
B) if you're old school you can photocopy wiring diagrams on to transparancy sheets and use an overhead projector to display it on the whiteboard. (if you're in the technoweenie camp, scan the diagrams and use a proxima type projector to display it)
C) It keeps munchkins occuied drawing pretty pictures while you're out there working.

I've been meaning to write it up for my web site, I'll put it on my to-do list. But, the basics are you go to Home Depot and buy the 4'X8' sheets of whiteboard. Also get insulating styrofoam at the same time. (this applies to garage doors that roll up and are built in horizontal sections). Insert the styrofroam anel into the door section, then cut to fit the whiteboard and screw it to the horizontal door frame section. Rinse, lather and repeat.

Or, if you have a single solid door you can buy the whiteboard material as a roll (akin to contact paper) and put it on the door/wall/dog/etc.

 

[Randy Forbes]

I'm betting it's shorted in one of the front wheel wells.

If the harness isn't clipped properly between parking and headlamps, it rubs on the tire exposing the copper.