My 96 Deville heats up(mildly) at redlights or stop signs or heavy slow moving traffic. I am not losing coolant.

I notice that my two rediator fans never come on. What controls them? When are they supposed to run? I assume that they do not run when the car is moving because ofthe natural air flow into the grill.

What is the normal running temperature?

Mike in Wexford PA

PS I just made an 1800 mile trip and did not have to stop for a problem. However I did notice the temp went to 216 at redlights and stop signs. The outside air temperature was from 30 degrees to 60 degrees during the trip.

 

The fans should come on at normal temperature or less. sometimes when u turn on the ac or the heater they come on. if they dont come on then u will need new ones or u might have a short on a wire.

 

What temps were you seeing? Under 227 and no fan normal.

 

Most fan sensors engage the fans at approx 220 degrees. The thermostat is a 195 so the engine runs between 195 and 225. degrees F.

 

Im not very familiar with caddy cooling systems, but theres usually a relay that is turned on by the a/c control head when u turn a/c on. and another relay that is control by the ecm that turns the fans on when the coolant temp sensor reaches a pre set temperature. (likely around 200 degrees) What I recommend u do first is turn the ac on and look at the fan to see if its operating. if its not operating then figure out where the connector nearest to the fans is and disconnect it. now using a jumper wire, jump power from the battery and a ground to the fan. if the fans working then you know that the problem isnt the fan. its somewhere else in the circuit. check relays, the harness where u can, and check the CTS (coolant temp sensor) its an NTC thermistor which means when tempurature goes up resistance of the sensor goes down. so if theres an open in the sensor the ecm is going to see a sensor default of something like -44 degrees. so if the ecm thinks the engine is running at -44 degrees, its never going to send the signal to the fan relay to turn the fans on.
bottom line it could be a number of things. just go from easiest to check to hardest