C4 Engine Cooling Fan

[sirfixalot]

Does any one know if when a C4 starts up when cold should the cooling fan run. It is driven via a relay from the Powertrain Control Module. The Powertrain Module has an input from Coolant Temp Sensor which I assume drives the fan via the Control Module. The Temp Sensor reads 71.5 ohms when cold.

[87Z51]

If the A/c is turned on fan will run any time regardless of engine temp.
If A/c is off and fan runs ; key on; is generally a indication of a PCM fault and the PCM is in limp home mode

[sirfixalot]

Any one else got any ideas on this problem. I assume I am looking at the correct sensor.  Sensor is located on R/hand side of motor at the front.

[gtc]

I assume I am looking at the correct sensor.  Sensor is located on R/hand side of motor at the front.

Dunno what year model you're working on, but some posts in this thread about an '86 might help:

http://forums.corvetteforum.com/c4-tech-performance/761685-second-cooling-fan-infront-of-radiator.html

[sirfixalot]

Car is an 86

[87Z51]

Any one else got any ideas on this problem. I assume I am looking at the correct sensor.  Sensor is located on R/hand side of motor at the front.

86 ;
Main fan is controlled by ECM from the temp reading from the CTS which is located under the throttle body at front.
The Aux fan  in  front of the radiator ( if fitted ) is controlled by a mech switch in the head between #  1 and 3 plugs
The sensor in the RH head is for temp gauge
If you have a faulty CTS then you will have more than fan problems because the ECM uses the engine temp reading to control all engine functions
Is the connector on the pressure switch on the A/c hard  line?
If it is disconnected or faulty the ECM will think the A/c is on and run the fans full time