Have been chasing down an overheating issue, only at idle and under acceleration. I believe I've finally narrowed it down to the AC Condenser fan, which makes sense because the AC stopped blowing cold about the same time I noticed the overheating.

I can put power directly to the fan and it blows fine, but when I turn on the AC the fan will not come on. I checked all of the fuses and relays under the hood, they all check out fine.

Any ideas what might be causing this to not work?

Thanks for any help.

-Tim

 

The A/C fan is not meant to come on with the A/C. It's programmed to work only in certain conditions as per RAVE:-

"Engine cooling fan control
While the A/C system is on, operation of the electric engine cooling fan, to assist refrigerant condenser operation, is determined by a combination of vehicle speed and external air temperature. When cooling fan operation is required, the ATC ECU outputs a cooling fan request to the ECM, which then energises the cooling fan relay. The cooling fan
request is output if vehicle speed is 50mph (80 km/h) or less while the external air temperature is 28 °C (82 °F) or more. The request is cancelled, and the cooling fan switched off, if either the vehicle speed increases to 62mph (100 km/h), or the external air temperature decreases to 25 °C (77 °F)".

The fact that your fan works at all is good, many owners here find that the fan has seized and they need to source a new one.

Your over heating is not caused by this fan not working, though the ECU can signal for it to assist with cooling if there is any over heating.

 

Thanks for the input. I thought it was supposed to kick on at idle or under acceleration when the engine got too warm. Obviously I can't check that under load, but the motor does get up to about 206-207 at idle, and the fan does not come on.

Does anyone happen to know what the threshold is for fan coming on at idle?

So temps going down the road are typically around 197, but if the truck downshifts to pass or go up a hill the temps climb pretty quickly. They go back down to the 195-197 range very quickly if I turn the heater on. At idle it takes a while, but will eventually creep back up to 205-206.

I've already replaced water pump, has new thermostat, flushed/bled the coolant system (even peeked inside the radiator with a scope, looks clean as a whistle), and I've swapped out the fan clutch with a known good one.

All indicators seemed to point to this fan not coming on when it needs to, but I'm open to any other leads you guys might have.

-Tim

 

So found more info on the fan, guess it doesn't come on until 225 degrees or so. I just get really nervous that I'm hitting 207 degrees in fairly cool weather, it's never happened before.

Again, any ideas you guys have would be greatly appreciated. Might start another thread specifically for the overheating issue, but I've researched the heck out of it and addressed every problem I've read about. Can't imagine another thread on the same topic would uncover any new information.

-Tim

 

Isnt it 210

 

It is exactly 212
Also if ambient is above 82f the fan should come on with Ac