Fog light switch-512 tr

Probably dirty contacts...not uncommon with age. I would suggest removing them, disassemble and clean the contact points with a mild abrasive and then flush with some electrical contact cleaner or which with an alcohol prep pad. Then reassemble. Had to do that with the window switches on my 78 308 GTS.

BTW, the problem could also be the relays that those switches activate, so you may need to check them as well. I had a problem not long ago with the hazard lights on my 355. After replacing the switch, it ended up being a bad cold solder joint on the circuit board inside the hazard light relay. I opened it up, touched up the bad solder joint (had to use an 8X lupe to find it) and all good. If I had to buy the relay, the thing was over $200. Takes your breath away...

 

Those switches are a miserable engineering design at best. Take them apart VERY CAREFULLY. There are tiny springs and a flexible triangle metal contact that will fly off and be gone forever in an instant. Take care to re-assemble EXACTLY how they come apart or they will not work.
BTW, I think you are referring to the front fog lights and the rear defroster switches?

Good luck.

 

+1 -- they are an active latching switch that automatically turns "off" when you turn the key "off" (so they can't be left "on"). Here are some photos of the internals that others had previously posted:
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I don't want to bog anyone down in engineer speak, but these switch are hamster poo.

They require a hard push and its difficult to tell if you've engaged or disengaged them. I took my hazard switch apart since it stuck in the first time I tried it. Upon disassembly, things tried to escape. Be careful. Got it back together, but am not looking forward to messing with these switches either.

That photo is super valuable. Thanks Steve.

 

I agree that these switches are miserable. Both fog lamps, front or rear, are the devil to activate. On three occasions when having the car serviced, I moaned about the problem and was told that it was because these switches don't get used much.

I think some of the other explantions in this thread are probably closer to the truth, i.e. dirt or poor relays. Still, I do now try to switch them on and off more frequently, hoping that they will become accustomed to my touch. A bit like a pet.