Radiator Fans only working with A/C on

[Dynomite]

Originally Posted by Franke

Is there really a problem here? Based on what I read in the FSM, it looks like the primary fan should come on at 234 degrees F + if AC is off. Engine oil temp also factors into the fan request as well so if the temps are not as high as the FSM indicates there would be no fans request from ECM.
You indicate the you were able to figure out engine data from A/C system control screen to verify ECM knows engine temp to activate and it does know correct engine temps. Just curious if it met these FSM parameters?

Good question

Originally Posted by MrsMcNastys

Hi Guys,
Thermostat appears to be working correctly, with A/C off reached operating temp and no fans activate, temp hovered at mid gauge range at idle then slowly crept up higher.
Turn on A/C - both fans kick on, quickly brings temp down below half way, cycles on and off - can idle for hours no problem.
Turn A/C off - no fans, let the temp climb quite a bit one time to see if fan activation was delayed - still nothing.
Any suggestions would be greatly appreciated.
Ed

It is not known from the description exactly what the coolant temperature was in degrees F during the testing.

As an aside......... Marc Haibeck's Calibration AYBKG (1990) Turns both of the cooling fans on at 205 degrees F. Both turn off at 200 degrees F.