I have an 88 GTA which has twin cooling fans.During the summer I noticed that the secondary fan (passenger side) would not operate at all, even with the air on and the engine at very high temp(e.g when idling in traffic, etc)but as these conditions were rare I wasn't too bothered. I did ground the coolant sensor wire from the unit above the starter & the fan will start so I guess that this means the sensor is bad(??). However the other night i noticed that the primary fan (driver's side) has now stopped running & I am a little more concerned about this....when the ALDL is in diagnostic mode (terminals A & B bridged) the fan will run so I guess all the relays & fuses are OK (??) and no fault codes are displayed. The only thing that I have done recently is disconnected the battery, and so reset the ecm but everything else is normal. Am I correct in thinking that the coolant temp sensor is located at the front top of the engine, underneath the air intake hose for the throttle body (5.7 litre)and could this be the problem?? I normally solve all these problems with my Haynes/Chilton manuals but they are both very vague on the whole thing. Any help you guys can give would be appreciated, it's pretty cold here at the moment but I need to get it sorted before spring!
Thanks guys, and Happy Christmas to you all!!

 

The second fan requires a temperature of over 300*F/151*C before the ecm will turn it on. Your first fan (Driver's) will turn on much sooner (226*F/108*C stock) and if your cooling system is working properly, it should be more than adequate to cool down your engine such that you never hit the condition for the second fan to turn on.

A lower temperature fan switch turn on the first fan sooner, but I prefer to alter the PROM for BOTH fans. I currently have my second fan to come on much sooner since it has seldom seen action, with my first fan coming on if it get 10*F hotter.

Another good reason to consider burning your own PROM. You don't have to buy an aftermarket fan switch which only works on one fan, its a hell of a lot easier to change than a fan switch, and you can alter it to whatever you want, whenever you want.

 

or you can get an adjustable fan relay, check the tech article, i put in the hayden one and wired it to both fans, can turn on btwn 90 and 210*

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