A couple weeks ago I noticed car was running slightly hot- checked it out and didn't see anything. Last weekend on the highway the tensioner pulley for water pump basically melted. Replaced tensioner and new belt. Noticed that mini relay for cooling fan 1 was blown. It had slightly melted the top of the fuse box. Replaced mini relay #38 with a spare numbered 3604. Pulled fuse box off and checked the module which connects to harness and it was fine. Ran car for around 100 miles no issues, temp was at 200 even. All seemed well....

Today the car was running slightly hot 210... Parked it saw that Fan #1 not running and #38 COOLFAN 1, was blown again. This time top of fuse box was slightly more "melted" and had to pry the relay off. Ordered another used fuse box ( my 3rd but nothing previously related to the fans).

Is there anything which would cause the mini relays to blow?
Is mini relay 3604 the correct one for COOLFAN 1 and COOLFAN2?
What does #39 COOLFAN S/P control?
Anything else to check?

Thanks

A blowing relay is pretty much the same result as a blowing fuse. Higher resistance due to a poor ground or short. So I would start tracing the circuit.

Could be a bad fan, could be bad connections at any connector within that circuit, could be the connections in the fuse block (you mention you've replaced that already).

Yes, 604 is a valid relay.

#39 controls the circuit to ground or to trigger the high speed fan relay if I recall.

_________________


Retired Bonneville Owner and former GM Tech:
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Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
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What is the difference between the mini relay and the maxi fuses for the COOLFAN?

How would i test the fan- it does run when the mini relay was replaced? So how would i know if is at fault?

In tracing this short would the best way to go about it? to take the nose off the car? or is all relevant wiring accessible from underneath the car? Will a mechanic's scan tool help me zero in on the fault?

I have been looking for a wiring diagram but no luck...