Radiator Fan always on when heater is on?

[norm86]

Hey guys,

I have something happening to my P5 that I'm curious about. Not sure how to explain it, so bear with me. So, everytime I turn on my heater, a fan turns on from the engine bay. I believe it would be the radiator fan, since I usually hear the same fan noise when my car starts to overheat. Anyways, the radiator fan turns on, and stays on, whenever my heater is switched on. As soon as I turn off my heater, the fan turns off. I don't know if this is normal because last year, I believe it only turned on periodically and when needed when my heater was on. Anyone know what could be the problem, or if this is actually a problem? Some other key points are: I changed my catalytic converter (under the manifold) this year, and my A/C is currently not working (no cold air blows, which probably needs more freon).

Thanks in advance!

 

[CheeseHelmet]

What position is the vent selector knob? Turn it all the way counter-clockwise (only the top vents) and try running the heater. Also, if you could tell us which fan comes on that would make diagnosing the problem easier.

 

[Tzar177]

Hey guys,

I have something happening to my P5 that I'm curious about. Not sure how to explain it, so bear with me. So, everytime I turn on my heater, a fan turns on from the engine bay. I believe it would be the radiator fan, since I usually hear the same fan noise when my car starts to overheat. Anyways, the radiator fan turns on, and stays on, whenever my heater is switched on. As soon as I turn off my heater, the fan turns off. I don't know if this is normal because last year, I believe it only turned on periodically and when needed when my heater was on. Anyone know what could be the problem, or if this is actually a problem? Some other key points are: I changed my catalytic converter (under the manifold) this year, and my A/C is currently not working (no cold air blows, which probably needs more freon).

Thanks in advance!

When you have the AC on, are you sure the green light is on on the AC button? Also, check the cable behind the AC/heater unit. It may have fallen off and is stuck in the heater position

 

[i12drivemyMP5]

Hey guys......this happens because they tried to idiotproof the car so whenever the defrost or heater is selected and the fan is turned on, the AC compressor is on to help keep windows unfogged regardless of whether or not the AC button is pushed in or not and it doesn't light the AC button either. Therefore, the fans under the hood run just like when AC is selected and fan inside car is turned on. You can just put it on heat or defrost and on fresh instead of recirculate and not use inside fan and air will flow thru and do it's job while car is moving and you won't be spinnin the compressor. Crack window to let air flow thru car and not fog windows. The other option is to cut one of the traces on the back of the climate control panel so the AC compressor will only run when the AC button is actually pressed in. There is a how-to called disabling auto AC....

http://www.mazdas247.com/forum/showthread.php?t=55382&highlight=disabling

 

[norm86]

Hey guys......this happens because they tried to idiotproof the car so whenever the defrost or heater is selected and the fan is turned on, the AC compressor is on to help keep windows unfogged regardless of whether or not the AC button is pushed in or not and it doesn't light the AC button either. Therefore, the fans under the hood run just like when AC is selected and fan inside car is turned on. You can just put it on heat or defrost and on fresh instead of recirculate and not use inside fan and air will flow thru and do it's job while car is moving and you won't be spinnin the compressor. Crack window to let air flow thru car and not fog windows. The other option is to cut one of the traces on the back of the climate control panel so the AC compressor will only run when the AC button is actually pressed in. There is a how-to called disabling auto AC....

http://www.mazdas247.com/forum/showthread.php?t=55382&highlight=disabling

Give this person a medal! Gave it a shot, worked like you said. Thanks a lot, and thanks to the others for the info. Now to the task of disabling auto-AC....

(drinks)