Radiator fan control?

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Old 10-18-09, 06:59 AM
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Radiator fan control?

While flushing the cooling system on my 1990 Plymouth Grand Voyager (3.3 v-6, auto trans, A/C and rear heat), I noticed the radiator fan cycled on and off maybe three times, then the next time it tried to kick on, it only stayed on for a second. I have not heard it run again since. This morning, I tested the fan (jumped the connectors at the relay connector and the fan roared to life) and the relay (grounded the relay terminal that the blue/pink wire goes to and the fan roared to life). My questions are: Where does the fan relay get its ground, through the PCM or from a switch on the engine? If on the engine, where is it? And, what is the single-wire switch threaded into the right side of the front(left) cylinder head (has about a 14-ga. orange wire going to it)? Is this the knock sensor, or would that be in the block somewhere? Hoping to drive to St. Louis next weekend, and don't want to overheat, so any advice is appreciated. Thanks - Chris
 
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Old 10-18-09, 04:02 PM
Join Date: Jul 2009
Location: Washington State
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Temp switches for fan control are usually located near the temp sender for your gauge /temp light some where around the thermo housing on the intake man don't recall if 90 used a switched ground or power but most obd 1 systems did not control this through the ecu it was more a hard wired thing.Id start with a relay replacment first since you can make it work by connecting it directly this elimantes wire or motor issues.
 
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Old 10-20-09, 06:21 AM
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Something has just occurred to me while flushing out the system, there was a LOT of rust that came out. Could the rust have affected the way the temp switch/sender was functioning? And/or, could the system flush additive have harmed the switch/sender? My Chilton's manual and my local O'Reilly parts house only show one temperature sensing device for this van - might it be a combination unit, feeding the gauge, ECU and fan relay all in one? Just thinking out loud, as it were... Chris
 
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