AC Fan Turning On When It Shouldn't

[romeen]

Whenever I turn on the fan for the climate control the AC fan kicks on even though the AC is not activated. Just started doing this out of the blue. I have FAL slimline fans. I have had them for several years now and it never did it before. Other than a boost leak test I have done no recent work on the car. Normally it would be nice to be able to control fan activation from the cockpit like this but the fans draw alot of current and I don't necessarily want it running if it's not needed. Has anyone experienced this before?

 

[luv2rallye]

Stock fans are dual speed but most Slimline are single so it's going to depend on how they are wired. If on each fan the positive hi and lo are wired to slimline positive and the negative hi and lo are wired to slimline negative (the way most people have them), the AC fan will come on when the ECU turns on the radiator fan hi (but not when it turns on radiator fan lo). This is because radiator fan hi relay is wired in parallel to AC fan hi relay to get maximum cooling when the ECU wants it.

If you want the AC fan to come on ONLY when the AC is on, just pull out the AC (condenser) fan hi relay. Keep in mind if you then overheat, the AC fan is not going to ever come on unless you turn on the AC. If you want manual control you could rewire that relay to a switch to force the AC fan on when you want - like overheating (in off position the AC fan would still come on with the AC like it's supposed to).

 

[romeen]

Good info. I'll be checking it out. Thanks.