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Re: Cooling fan??? Posted by Ari [Email] ![]() ![]() In Reply to: Cooling fan???, Dave, Thu, 19 Jun 2003 05:08:33 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'd have to check a schematic on this one, but I'll bet it's the cooling fan relay.
On some years, the cooling fan relay had a time delay feature. This would keep the fan running for 10 minutes after the car shut off. The relay turns on if the thermo switch on the radiator says the radiator is hot.
Here's the tough part - without a schematic, I'm not sure if the '87 had the time delay relay. There was a service bulletin for '89 900 and later cars to replace the time delay relay with a regular one. But the bulletin mentions that in '89 and later, the time delay relay was directly interchangeable with a non-time delay relay. I'll bet there was a time delay relay earlier (like in your '87), but it just wasn't a driect drop in.
So - two possible problems. First, what Dan said. If the switch on the radiator is faulty, the fan would come on as soon as the car was started, independent of temperature. And the fan would run for 10 minutes after shutting off because of the time-delay relay. Look at the radiator for the switch - it screws in, and would have one wire coming out the back. Make sure the wire isn't shorted to chassis. Pull the wire off, and use an Ohmmeter to check the resistance of the connection to ground. With a cold car, it should be an open circuit. If the switch is a closed circuit (a few ohms) with a cold radiator, the switch is faulty.
It's possible that during the recent radiator work someone damaged the thermoswitch, or somehow screwed up the wire. Or, if it was a brand-new switch, it's faulty.
If the switch checks out OK, it may be a bad time delay relay. Thats the "Fan" relay in the relay box in the engine compartment. This relay isn't cheap, so make sure you troubleshoot the fan switch first.
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