On a 90 chev lumina sedan with a 3.1 when the a/c is on should both radiator fans be running?

I have been having a overheating problem. It only happens now and then. The car dumps collant threw the over flow tank.





The reason I am asking about the radiator fans is to try to elimanate the problem threw testing and not just changing parts.





I NEVER hear the fan or fans running. when I turn on the a/c only one comes on. I think they both are to be running but I'm not sure.





Any ideas??





Thanks





Al T.

On a 90 chev lumina sedan with a 3.1 when the a/c is on should both radiator fans be running?
you are right, both fans should be on when you kick on the AC and only one when the AC is off.
Reply:the fans should come on to lower the pressure in the a/c system. I work on big trucks and when the a/c gets turned on the pressure gets to about 300 350 then the fan comes on to get that pressure down before the lines blow. dunno if that helped but yes the fans should come on and off as the pressure rises and falls
Reply:its the relay i kow it becuz i have the same car but its a 96
Reply:Actually on the lumina, chevrolet designed the fans with seperate circuits. The driveside fan only comes on when the engine temp reaches a certain degree.


The passenger side fan is for the A/C and only comes on when the a/c is requested, does not run off of pressure switch like most.





If your having a problem with the car overheating and your engine fan isn't running, then I would check the temp sensor


(this is seperate from the temp sending unit which controls you gage on the dash.) for the computer, the cooling fan relay, and lastly the fan itself.





Hope this helps!
Reply:This is something you wont to take care of ASAP. overheating of this engine can blow head gaskets, warp the heads and cause the intake manifold to leak. Have your cooling system pressure checked. A bad radiator cap will let the system loose pressure and overheat. A bad thermostat can also cause overheating. Start the engine and turn on the A/C, open the doors and run the A/C on max. Block the front of the car with a large towel or something to restrict the air.. When the top hose starts getting hot one of the fans will come on, when the hose is to hot ti touch the other fan should come on. Watch the temp. don't over heat the engine. If the second fan doesn't come on, it is most likely the thermostatically control switch on the engine block that is bad or the fan motor. Also make sure the condenser coil is not restricted with bug and dirt, it's in front of the radiator and can be washed out with a water hose.
Reply:The cars that I've seen that have two fans have one that turns on when the car is hot, and one that turns on when the a/c is on. Also, sometimes when the car is very hot it can turn both of them on.





Don't know on you car inparticular though.
Reply:Both fans should be on when the AC is engaged. Check the electrical connections with a DVOM to see if you have power to both fan motors when AC is turned on. If so, then check the fan motor itself. If the motor has gone south it is a very simple replacement.
Reply:I have only had this happen once in over 60 years of driving and looking after my own cars. I was having the engine running hotter than normal and while looking at the operation of the cooling fan motor I noticed it seemed to be running slower than usual, I looked at my other car and found that the fan was running normal and the 1st car had a motor that was running but slower. Didn't think this was possible so I installed a new fan motor anyway, that was the answer.