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Wiring details of headlight switch?


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I have fuse blowing issues with the wire that goes from the fuse box to the headlight switch and then to the gauge lights. There is a short somewhere and I'm trying to figure out the wiring. The factory manual is no use as the wiring details in the switch are not really shown. The wiring diagrams show the switch but the wiring within the switch are shown so light that it's impossible to see what goes where and there are a lot of wires coming out of that switch.


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Guest Anonymous

Year - model - # of fuses - modifications?

Do you own, know how to use a VOM?

Here's some 12 fuse info -

Headlight switch -


Schematic front -


Schematic rear -


Key -


Also - try a search - these same symptoms have appeared here recently.

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Thanks, it's a 1973 with the 12 fuse system. No mods. Yes, being a lifelong Fiat nut I have spent much quality time playing with VOMs. Headlights and side marker lights work fine but if I plug in the wire wire that goes from the fuse box to the gauge lights it pops when lights turned on. And that's with the dash gang plug not even plugged in. Maybe a bad switch?


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I think I may know the answer...there's an extra wire attached to that fuse that isn't on the factory wiring diagram--it goes to the seat belt warning light and that circuit contains the switch in the front seats that causes the light to stay on if you don't fasten your seat belt.

I had the same problem as you did with my '73, and finally traced it down to this mystery wire--the seat belt switch in the seat itself was shorting out. If you'll drop me an e-mail, I'll dig out the column I wrote on this problem (with the wire identified) and send you a copy. This problem was a real puzzler until I discovered that extra wire and what it did.



'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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