I started turning on the AC the other day - it is usually cool here. I noticed the running temp of motor will quickly jump 15-20 degrees when I turn on the AC (60mph highway cruising). Turn AC off - temp drops down to 185-190 again.


I wouldn't think that turning on the AC should have such an effect - maybe too much freon charge? Is this normal behavior - outdoor temps were 70-80 degrees???


thanks,


jeff

dont make sense that it should jump that much, but the first thing I can think off is the warm air is being pulled out of the condensor, which mounts in front of the radiator. All that warm air goes right to the radiator. But I doubt thats the complete case.


Does the fan kick on ?

It is normal for the motor to run a bit warmer due to the condenser in front of the radiator like Eric said! The heat has to go somewhere... It is odd that would cause a spike in your temps right away though. Could it be some sort of freak electrical thing that is tied to the switch? I'm guessing there, but this is a wierd one...


Later.

I don't know if the fan is on or not - would it "need it" at 60 mph running down the highway at 60 degrees F?


When I say it changes temps quickly - I'd guess it climbs in temp to a new, higher stable temp in less than 30 seconds. I am surprised by the delta change and don't recall it doing this last summer...


Time for me to do the simple stuff like pop the radiator cap and see if the coolant is full (the reservoir is good).


thanks!,


jeff


Edited by: dmax lover

My engine doesn't blink in winter when I recirculate or in the middle of July up 5 miles of 6% with 10K in tow. This is the first truck I have owned that I could not feel the compressor cycle on and off. I would say at 60 MPH at the ambient temp you were pulling across the radiator the engine was not up to temp until you turned on the A/C. Later! Frank

I thought this too - until I turned off the AC and the engine temp dropped 20 degrees. Cycled the AC on and off again - up 20 degrees and down 20 degrees. Repeatable and spooky...


It didn't do it on the way home - Maybe I was just in the "zone" between the 180 degree thermostat and the 210 degree thermostat... (there are two. right?) It didn't do it on the way home... 85 degrees outside and 205 degree engine temps all the way home - AC on or off...


I will have the AC checked on the next trip to the dealer.


- jeff

I don't know...I towed my 6k trailer this past weekend in 95 deg temps w/ac on, engine temp didn't budge. I think there is something to check. Not sure where to start though.





Bill