Engine cooling fans always on


#1

My wife’s commuter car is a 1997 Acura CL 4-cyl with 238K plus miles.

After cleaning the IAC valve because of rough idling I noticed that both engine cooling fans are always running when the climate control is set to heat or A/C or something in between. I know with A/C on the fans are running, but I was surprised to see them running when any setting of the climate control is turned on. This is regardless whether or not the engine is cold or hot. With the climate control turned off the fans will also turn off (unless they are running because of a hot engine).

I worked on the car before and don’t recall seeing the fans on at all times. Is this normal?

Btw, cleaning the IAC fixed the rough idling.


#2

The IAC valve is controlled by the engine control module, which will adjust the idle speed according to parameters such as [engine temperature]. I guess its not reading right if you have both fans turning on when they are not suppose to.


#3

Possibly you are right. However, turning the climate control off also turn the fans off and work, as I think, they should. Only come on if the engine temperature is high. Therefor I assume other related sensors work correctly.

I did notice that the RPMs slightly rise when the elctric fans are running.


#4

Some cars do that on purpose, to prevent the engine from slowing down too much and possibly stalling when the fan comes on due to the electrical load on the alternator. Often the same thing happens when the headlights are turned on, the steering wheel is turned, or the rear window defroster is turned on. As far as the engine fans, they should be on when the AC is on probably, but I can’t think of a reason why they’d be on when the heater only is on. Maybe the way it works when the climate control is on, the AC is always on and it blends a certain proportion of cool and warm air to get the temp desired. In that case the fans might be on all the time the climate control is on. On my Corolla the fan is controlled by the coolant temperature only. That sensor has failed three times in 26 years, and sometimes it has failed in the on position, which causes the fan to run continuously when the engine is running. Sometimes it fails in a way so the fan turns on and turns off whenever it feels like it. If the connection to the sensor fails or is unplugged the fan runs whenever the engine is running, designed as a fail-safe I guess.