Cooling Fans

[GTO1967]

2003 Pontiac Grand Am V6. Cooling fans do not turn on even when I turn the A/C on. I replaced the thermostat and cooling sensor which didn't solve the problem. When I unplug the cooling sensor the fans work. Any ideas on the cause?

[brcidd]

Here we go again- what are the parameters that need to be met to activate cooling fans on an "N" car?? is your question. And what makes you think you have an issue?

So here it is- the mere fact that you unplugged the cooling sensor and fans came on is a big indicator that the system IS working and that perhaps you don't understand HOW it works.

Just because AC is on, does not mean cooling fans come on- Most cars now are economy-minded and actually wait on ac head pressure to build to 175 psi before turning fans on at low speed. So unless it's about 95 degrees out, you'll not see a fan come on-- plus, they do not wish to use fans when there is adequate airflow while moving down the highway speed. You can know for sure by noting that your AC system has a three-wire transducer on the high-pressure line which does several things- like shut off the compressor at 425 psi and activate cooling fans at 175 etc..Older systems as you noted, merely turned on the fan with ALL ac activation not any more...

So is your engine boiling over? Is coolant gage near the red? If not, I suspect that that is also okay. Cooling fans usually do not come on low speed until ECT (engine coolant temp) hits 227 or so. And usually, to make this happen you have to cover the hood with blankets, block nearly all airflow and rev the engine up to get it hot enough. Just idling at 75 degf ambient probably won't raise ECT enough. A scan tool can also monitor ECT and you can also use it to test (activate) the fans.

[GTO1967]

Sorry I forgot to mention that the car does overheat. If driving on the highway the car is ok with the airflow. But on idle it overheats since the fans don't come on. Any thoughts are appreciated.
Thanks