hot headlight switch!

[jayhawk]

Well, my evening cruise was foiled again!-- About a mile into our ride around the boulevards of Kansas City on a nice night-- started sniffing that "electrical" smell and stopped at a little shopping area-- felt around under the dash and got a little burn on my finger-- the back of the light switch and wire on the dash were burning hot...

tried to feel (its dark) if anything was touching around the dash area but no (more finger burns). Drove it home quickly and check with the flashlight to see a hot slightly melted wire from the ignition to the light switch but nothing obvious.. Anyone had similar prob-- where to start? I've started looking at wiring diagrams, will check the switch, the dimmer switch, etc for bad connections, etc.


Thanks in advance, Pete

 

[Geo Hahn]

I have had this occur on the TR4 when the internal contacts got dirty, increasing resistance w/i the switch. Switch still worked but got really hot. I was able to take it apart and clean the contacts... have never had the TR3 switch apart... you might get away with cleaning the connections on the back and assuring they are nice and tight, if the resistance is internal then *maybe* spraying some WD40 in there and working the switch vigorously will help.

Check resistance before and after to see if you have done some good.

 

[jayhawk]

Thanks again Geo. As usual, you're probably right on track. Dunno yet about the internal contacts but the switch itself was a little loose in its mounting and the wire from the ignition switch to the headlight switch was not tightly secured and showed damage from the heat/arcing-- (arc-ing is that a word? arc definitely is, but never used that tense in a sentence!)
Thanks, Pete

 

[waltesefalcon]

I'd say Geo nailed this one, those old switches are actually pretty notorious about this kind of behavior, as they start to get dirty.

 

[jayhawk]

As it turned out, the switch was not only dirty but the lobe that connects the hot wire from the ignition was actually broken-- I tried cleaning it up and gluing it back together but it didin't work. Part of the plastic back holding the connector/set screw was missing so I can't get a good tight connection. On to the task of finding a new switch.

Pete

 

[jayhawk]

Re: hot headlight switch! follow up

I know it's a small thing, but I sure like it when something I do makes things work better. I put in the new headlight switch and everything works better than before--brighter lights, brighter dashboard lights and no hot wires or switch. I suspect the old switch has been broken with poor contacts the entire time I've owned the car (1.3 years). I previously had to wiggle it sometimes to get the lights to come on. If a hot switch or weak,intermittant lights are a problem, cleaning it or checking it for wear/cracks, etc is a good fix.
Pete

 

[dklawson]

Re: hot headlight switch! follow up

FWIW, most Lucas headlamp switches have trouble eventually. One way to extend their life is to add headlamp relays. The dash switch and dimmer only have to supply a minimal amount of current to the relay(s) in that situation so your switch and dash wiring experience less wear and tear.

I'm glad your new switch resolved so many issues!