What causes the fan to turn on???????????? Mine wont!!!!!!!

[rivera]

1991 chevy corsica 3.1 L V6:

Radiator Fan will not turn on unless I disconnect the coolant temperature sensor plug (replaced sensor with a new one). It will also turn on when I ground any of the 2 wires going to the CTS and then turn off within a minute. I do not want to leave the sensor unplugged and have the fan running continuosly unless i might have a problem with doing that. Any inputs as to this problem greatly appreciated.

CR

[sharkey]

your ecm turns the fan on. it sounds like your relay is working. when you unplug your tempeture sensor, the ecm thinks the engine is at max temp so it turns the fan on.

what is it showing for temp on the gauge??? is it getting real hot??? in cold weather, the fan may not turno on at all. usualy fan turn on is at over 200 degrees, and in cooler weather, you may not see those temps.

[rivera]

Sharkey:

Thanks for that. The temp gauge goes to the extreme right (past the red) and no fan. Is there sometning that can be check on the ECM?

Thanks again.

[TheProfessor]

you could always hook up a switch to the inside of your car that when turned on would trip the relay and turn on the fan

im going go guess that what is wrong with it is in the relay to ground circut
maybe a bad ground
thats where i would look first

[xtremesunfire]

its probley your thermostat is junk or your cooling sensor is bad

[Rhedalert]

yeah there's 2 coolant sensors: 1 for the ECM and 1 for the gage. Maybe your gage one is bad (screws into the back head)

[Syn]

yeah there's 2 coolant sensors: 1 for the ECM and 1 for the gage. Maybe your gage one is bad (screws into the back head)

he said the gauge goes to hot when the fan isn't on, sounds like it work the gauge is saying the engine is hottt as a result of no fan

hook a switch up and ground the fan relay and see it that will turn the fan on, its a green wire with a white stripe iirc. if it works that way you could leave it (ghetto) but it would fix the problem

[Juglenaut]

Redundancy turns on the gauge if the sensor is unplugged, shorting the sensor will make the ecm think the engine is hot.

The ECM doesn't govern the fans operation as far as if it is running or not. It also may only detect if the current to the fan relay trigger is to high and faults a code. However this is not a OBD-II so It may just trigger and internal fault.

I would replace both relays for the fans first then the CTS sensor, if that doesn't work replace the ETS and the T-stat. At worse the ECM may have burned up a trace associated with the fan control portion. A PAC-2000 would take the place of the control in the ECM which can be calibrated to any sender.

[xtremesunfire]

its either your theromstat is junk or your cooling sensor is junk or u just didnt plug it back in