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I have a 2002 c5 only one fan is turning on and can’t run the ac does anyone know where I should start checking for problems. Checked the relays they seem to to be ok
need help asap it’s hot as hell in H town
Last edited by Dwhaynie; Jul 11, 2019 at 06:56 PM.
You need to provide more details: which fan, what happens in low and high modes, coolant temperature, what happens when a/c is turned on, etc.
In each speed setting both fans are supposed to run at the same time.
There are 2 fan circuits:
Low Speed (½ the speed) - fans configured in a Series Circuit where ½ the voltage is applied to each fan.
High Speed (full speed) - fans configured in a Parallel Circuit with full voltage to each fan.
These are the schematics with the current path superimposed for each speed setting to help you troubleshoot your problems.
Since the Low Speed mode is configured as a Series Circuit, any interruption along the current path should affect both fans.
On the other hand, in a Parallel Circuit it's possible to have none, both or either one.
I'm including here a description of how fans are commanded, so you can compare it to your car.
NORMAL fan operation on a C5 is as follows:
Low Speed - Triggered when coolant temperature reaches 226°F. When the coolant temperature drops to 219°F then the fans are turned OFF.
High Speed - Triggered if the coolant temperature rises to 235°F during low speed operation. When the coolant temperature drops to 226°F then the fans drop back to low speed.
With AC turned ON the cooling fans come ON in low speed mode when the coolant temperature is about 185°F. The fans remain ON in low speed mode until coolant temperature reaches 235°F, then they go into high speed mode.
If the vehicle speed exceeds 35MPH the PCM turns OFF the fans regardless of the coolant temperature. Air flow through the free-wheeling fans should be enough to keep temperatures within parameters, as long as the radiator fins are not plugged up. If they are plugged up, then the coolant temperature will rise and the fans will NOT come ON unless the car goes below 35MPH.
Cooling isseues
