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MG TD TF 1500 - driving lights/headlight switch problem

My TF has the typical lucas driving lights. I was driving the car at night a few weeks ago and wanted some more light so I pulled out the driving light switch. The car went dead as if I disconnected the battery. So when I got home I tested it and got a nice plume of smoke from the headlight switch. So I bought and installed a reproduction headlight switch. Headlights worked great. I even disconnected the wire from the driving light switch and connected them together. So then I had driving lights and headlights all working fine. Tested the driving light switch and it was not working. Took it apart and got it working sort of ok. Put it back in turned the headlights and then pulled out the driving light switch and promptly smoked another headlight switch. Before you jump to conclusions, my driving lights are fused and the fuse has held so that would eliminate a short as a cause. I don't get it. The headlights work fine until I add the load from the driving lights via the switch but no problem if I isolate the switch. Weird... what am I missing?
BEW Brett Wright

Only thing that jumps out at me is the possibility you have some high wattage bulbs and the combined draw is more than the switch can handle.
MG LaVerne

I agree with LaVerne, the combined current for both sets of lights is overloading the capacity of the switch. An easy way to correct this situation, is to put each set of lights on separate relays, with the existing light switch controlling the relays. Another thought, if the driving light switch is separate from the headlight switch, then simply change the input for the driving light switch to a different source of power rather than running it through the headlight switch. If you want some help determining how to wire the switches and/or relays, e-mail me at SUfuelpumps@donobi.net Cheers - Dave
D W DuBois

All of the bulbs are normal wattage as far as I know. Also keep in mind that the entire load did not seem to be an issue in the past and when I bypassed the driving light switch.
BEW Brett Wright

I would say that you have a direct short to ground between your fog lamp switch and your fuse. Bud
Bud Krueger

This thread was discussed on 25/08/2014

MG TD TF 1500 index

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