Expert: Roland Finston - 10/6/2011

Question
2000 plymouth voyager 3.0L cooling fans wont come on.jumped 12v to fans they run. changed ect sensor,fan relay, radiator, thermostat still no luck. have 12v on grey wire at relay plug jumped across to green wire fans run.also temp gauge stays normal mid range even when coolant runs over to reservoir overheating. is the engine temp sending unit and engine cooolant sensor the same? if not where is the engine temp sending unit? tested wiring all ok any suggestions?

Answer
Hi Daniel,
There are two coolant sensors: the one on the side of the thermostat well is for the gauge and has a single wire, the ect for the pcm/fan relay operation is on the top, between the distributor and the thermostat housing and has a 2-wire plug. So maybe you didn't change the correct sensor. The resistance across the ect sensor should be about 700-1,000 ohms at normal operating temp, and should provoke the fans when it goes lower than that. Fluid will enter the reservoir due to expansion of the fluid, and only when it fills that or steams comes out are you overheated. You might not have the thermostat positioned in the well properly in that the bridge across the top of the thermostat should parallel the casting divider in the well, and the air vent should face forward. So check out those possibilities.
Roland
PS Sorry for the delay but I just found your question in the "pool" to which it had been referred by Kevin.