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Thread: Cooling Fans not turning on

  1. #1
    Join Date
    Aug 2008
    Posts
    3

    Unhappy Cooling Fans not turning on

    1997 Grand Prix GT

    I've been having what I believe to be overheating issues for the past couple years. I say this because the temp gauge would remain around what I think is normal operating range while driving but climb to about the 3/4 mark (which isn't far from the red zone) while idling or driving slow primarily on hot days. During the winter, the temp gauge never goes above normal operating temperature. Some forums I've read suggest that this might be normal tho this is the first car I've owned that's done this. People have told me that it takes a little longer for the heater to warm up the car in the winter than they're used to (10-15mins driving) but it will warm up and get quite toasty. I assumed the cooling system was just doing too good of a job but couldn't explain the issues during summer.

    This summer it's worse. I'm now having to sit in traffic for longer periods of time as my job finally is putting me in rush hour traffic and the temp gauge never actually touches the red zone, but it is getting uncomfortably close and I believe I can hear the engine sound changing at this extreme end. When the temp even gets near the 1/4 mark, the "low coolant light" turns on... but the system has never been low on coolant (I check reservoir and radiator both). Even while driving on the highway on moderate days (outdoor temp around 75-80), the temp gauge stays around 1/4 mark and low coolant light on. If I drive slow or sit at a light, it climbs up rather quickly... then goes back down after 5-10mins of driving. I'm now resorting to driving with the heater on full and the windows down... it does seem to help keep the temp gauge down.

    In trying to diagnose the problem, I've found that the cooling fans are not turning on. If I hit the A/C, they do (both). But now I'm keeping a closer eye on them and even after driving, if I stop at the store and think of it, I'll pop the hood before turning off the car and check the fans... still no go. But I have read forums that say they may not be programmed to turn on until the temp gauge hits the 3/4 mark and I have not yet looked at them when the engine is that hot.

    What I've done so far;
    professional flush first
    shadetree backflush several times
    new thermostat and radiator cap
    checked fuses for both fans... still intact

    My research so far suggests the problem is down to the relays, wiring, computer or computer input. What's my next step?

  2. #2
    Join Date
    Jan 2007
    Posts
    4,850

    Default

    Hi ragingmedic,

    First thing, run the engine until it's up to normal operating temperature, then let it idle and see if the fans come on (make sure the A/C is off) when the temp gauge starts to get near the red. If the fan doesn't turn on, start diagnosing the system. Check to see if there are any stored trouble codes - if there's a problem with the engine coolant temperature sensor, the cooling fan won't work properly. If that's OK, the relay (or the circuit) could be the problem.

  3. #3
    Join Date
    Aug 2008
    Posts
    3

    Default

    Ok, will do... I assumed that if the temperature gauge worked, the coolant sensor was working

    So are you saying that the fans are *not* supposed to turn on until the temp is way up there?
    Last edited by ragingmedic; 08-27-2008 at 07:16 PM.

  4. #4
    Join Date
    Jan 2007
    Posts
    4,850

    Default

    ragingmedic,

    No, just saying to check to see if they eventually come on at all.

    The low coolant light is controlled by the "low coolant module," located on the right-side radiator tank.

    Another thing to consider is that the temp gauge isn't really giving you a reading in degrees Fahrenheit - it's just a "relative" indicator as to the engine's operating temperature. Maybe everything is OK. But the fans failing to come on, even on hot days, is a concern.

  5. #5
    Join Date
    Aug 2008
    Posts
    3

    Default

    Well... I let it idle for a half hour... even drove it around then let it idle again but the day just isn't all that hot today... the temp gauge only rose to just above half :shrugs:

    I guess I'll have to wait until the next time the gauge goes up.

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