I have INTERMITTENT Fuse Blowings

[Bruce Adams]

I have had an in-line 30-Amp fuse between my 6 volt Alternator and the horn for fifty thousand miles without problems UNTIL LATELY.
Lately it blows while either driving or with the battery switch off, or maybe just prior to the switching off. It is independent of engaged hi or lo headlights, parking lights or horn. I note that I have a small coolant leak at the rubber hoses which I will address tomorrow in case it finds the fuse or wire.
This evening while driving, it blew with the lights on, and I saw them just turn off without a flare beforehand.
Yesterday it blew, I think when parked, on a 90 degree day. It did not blow at night, lights on, on the fifteen mile trip home, 75 degrees.
Sunday it DID NOT blow on a twenty mile drive in heavy traffic on a 90 degree day,
Last week it blew twice.
I had some body shop work on the R/F Fender two weeks ago, requiring its removal.

The 30 amp fuse at the starter has never blown.
I would appreciate your considered thoughts.
Thanks for your thoughts.

[Gary WA]

Why not remove all together? Or check to see if it blows while braking?

[Synchro909]

Hmmm, so the mudguard has been off and refitted, then the fuse started to blow. (That sucks!) When the mudguard was refitted, was a wire pinched somewhere. I suggest following each wire in that part of the car from end to end to check it out.

[Dave Slater]

Remove the fuse, solder two wires to a working headlight globe, attach the two wires where the fuse was. Keep an eye on the globe and when it lights up start looking for the short. Dave

[Synchro909]

Originally Posted by Dave Slater

Remove the fuse, solder two wires to a working headlight globe, attach the two wires where the fuse was. Keep an eye on the globe and when it lights up start looking for the short. Dave

If the short happens at night, you've got it licked!!

[KGBnut]

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Originally Posted by Dave Slater

Remove the fuse, solder two wires to a working headlight globe, attach the two wires where the fuse was. Keep an eye on the globe and when it lights up start looking for the short. Dave

I've never thought of doing that. That's a great way to hunt down an intermittent short (without eating up all my fuses).

Ken

[Big hammer]

Originally Posted by Synchro909

Hmmm, so the mudguard has been off and refitted, then the fuse started to blow. (That sucks!) When the mudguard was refitted, was a wire pinched somewhere. I suggest following each wire in that part of the car from end to end to check it out.

My thoughts of the dreaded head light connections, never thought about a pinched wire! When I was working in general aviation we came on a problem with an aircraft that the landing gear would not work unless the anti collision lights were on :-( The owner took it back to the people who caused this, they had drilled into a wiring harness.

[Kurt in NJ]

Most likely they had the headlight bar off---take the horn cover off and see if the cover or wire installation is on correect -if the conduit is in the proper place, or is it hanging by the wire---look at the headlight connecters ---is all the wiring stock and original parts --or has it been modified, whenever there is a problem start with whatever has been modified from original

[BILL WILLIAMSON]

I got my horn cover on crookedy & caused an intermittent SHORT.
Bill W.

[Bruce Adams]

THANK YOU FOR ALL THE GREAT IDEAS !
I will investigate the brake switch circuit and will do the head lamp trick prior to pulling things apart.
I will advise when solved.
Bruce