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## Re: Hot Light Switch

 To: mgs@Autox.Team.Net Re: Hot Light Switch rdonahue@holli.com (Robert J. Donahue) Tue, 1 Jul 1997 01:18:46 -0600 (MDT)
 ```>Mark Moburg wrote: >> In any event, when you run any current through a >> wire, it will heat up. How much it heats up is a factor of how much current >> you put through it. Your lighting switch carries all the current for the >> head lights, front marker lights, side lights (if you have them), tail >> lights, licence plate lights and dash lights. No wonder the poor thing is >> sweating. > > Sure. Just to extend this, the heat is caused by current through >a resistance. > > Every wire, every join, and every connection is a resistance, >and could develop some heat. I know that the contacts in the >switch are probably a fairly high resistance, so some heat is >to be expected. > > I guess my roundabout question is really asking if my switch >is making a poorer connection than it should, leaving a larger >resistance and a greater source of heat. > >-- >Trevor Boicey >Ottawa, Canada >tboicey@brit.ca >http://www.brit.ca/~tboicey/ > > I noticed that the light switch on my TD runs warm. A little investigation revealed that the hot part was a flat metal strip on the back. I believe this to be a fusable link and the heat is probably normal. Off hand I would say that a plain switch should not have enough resistance to run "hot" but a fuse has a deliberate amount of resistance and will be quite warm when running near it's rated current. Even though there is no distinct fuse in the headlight circuit, I bet something was designed to give in case of a hard short. Something you could do is measure the voltage across the switch. If it is something over about a half a volt, it has too much resistance even if it has a built in fuse. (I'm just guessing at this half a volt, has anybody measured this on a known good switch?) Bob Donahue, Still Stuck in the '50s rdonahue@holli.com 53 MG-TD #17639 under DIY restoration, NEMGTR #11470 71 MGB still in shop, 17 months and counting  ```
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