radiator fan works on high, but no low-speed

On our first 70 degree day my 1995 850 turbo wagon coolant the coolant at stop lights. I had a shop install a new coolant temp sensor and thermostat and radiator hoses for good measure and asked for electrical troubleshooting on the fan not coming on. They said the fan doesn't work on low speed, will need new one at ~$500. I'm confused as to how the unit can be bad if it the high-speed still works.

I read-up here and after a bit of testing, it turns out my 5-year-old aftermarket fan only turns on with 12v applied to the high-speed female lead from the fan assy. Nothing happens when 12v is applied to other female lead instead. I suspect this means my fan assy. is still good and I should fix it, not throw it away, but I need some suggestions on where to go from here. I have yet to cut into the wiring harnesses but I can only suspect that I have a broken wire on the low-speed circuit, yes? Are there other things to consider/test? I am a beginner at this kind of thing so any advice on theory as well as test strategies would be greatly helpful. Thanks all.

Reply to
Kurt
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No, it most likely means the fan assembly has failed. If it hasn't failed, and is supposed to have 12V applied for low speed, it should run when power is applied.

An easy test would be to swap the high and low connections, so that when the low speed should be active, the fan should come on at high, then slow down as the car warms up. Verify that the fan should have

12V applied to the low speed terminal first.

A safer test would be to use a couple of cheap multimeters attached to the high and low speed wires; start the car and see if voltage is indicated when the fan should be at low speed on the low-speed wire; if you see anything there, then it drops to zero and the other meter shows voltage on the high-speed wire, it's confirmation your fan assembly is bad.

$500 seems a lot for a fan and swap, though.

This one looks like it'll fit; at $141, they want $359 for labor.

Gary

Reply to
Gary Heston

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