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Circuit breaker in line with fan relays failing???

moosomoosoMember
I've been experiencing overheating. I have a new aluminum radiator with a thermal switch that grounds the fan relays to activate the fans after the water heats up.
After overheating yesterday, I opened the hood with the car running and the fans were not running. I shorted across the thermal switch to ground the relays and still...no fans.
I measured the voltage on the pink wires on the fan relays (12V input) and got less than 1 volt. After the car sat for 20 minutes, the fans came on as expectecd. The pink wires were now reading 12V.
It appears there is a circuit breaker between the key and the fan relays. Where would I look for this thing? I have a manual but it doesn't have a wiring diagram. Where can I obtain a full wiring diagram for a pre-L '72?
If anyone is familiar with this circuit breaker, is is "special" or do you think I can obtain a replacement at a good parts store?
Thanks, Mooso.
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R roverltdMember
No circuit breaker that I am aware of. Everything is off the fuse box, so it could be a lose connection in the fuse box those tabs are know to expand and contract. Best to get a wiring diagram and check it out. Was the temp switch wired correctly and turns on at temp and not backwards where it turns off at temp? Also check the two relays, they could be the real root cause.

Chuck has the diagrams online http://geocities.com/provamo72/
moosomoosoMember
Yeah, the thermal switch is OK. It is not on when you start up and comes on when the water reaches about 110 (by the guage).
I thought of the realys, but I would expect them to fail one at a time rather than both at exactly the same time.
The key to this seems to be that the 12V power wires on both relays read less than a volt when the fans were not working, but read 12V just a few minutes later when the fans were.
I found a 20A breaker in the fuse box. I cannot tell for sure, but it kinda looks like an add on. I'm going to replace it with a fuseable link so I can watch it blow.
I'm going to look through my installation guide on the radiator to see if it lists the draw on the fans. 20A seems a little low for two big fans. If the 20A blows, I may try a 25A or 30A.
I'll post what I find. Hell, I don't even know if this breaker is the right one!
Mooso.
moosomoosoMember
Well, it looks like that breaker was the problem. Replaced it with a fuse and the car is running cooler than ever before and the fuse hasn't blown.
The original fans had been replaced with aftermarket cheapies. When I got my new radiator it came with new fans installed.
The original wire insulation was pretty "crispy" when I stripped it to replace the breaker. I'll bet the original fans were shorting and were prone to blowing fuses and a previous owner put in "AutoZone" fans and a breaker.
He's probably the same genius that wired the fans backward and pulled out the thermostat! Sheesh!!

Mooso
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