So I have a 98 and as thread title says when defrost selected e fan will run until another setting another than defrost is selected. Was thinking maybe CTS? Or not. No luck with searching either CF or google. Thanks in advance

 

The e fan cycles with the ac compressor. I wonder if the compressor clutch is sticking.

 

I don't think it's the compressor clutch. When either foot or vent is selected the fan doesn't run. Only on defrost or defrost/foot. The idle raises slightly too which it's supposed to. But only the compressor is supposed to cycle under certain circumstances when defroster is on not the fan. I was hoping there would be one obvious straight up answer for this. I'm also experiencing a really rough idle and major skipping without any CEL. was hoping that if the CTS would cause fan to run maybe it was causing the other issues. But a bad CTS would probably cause the fan to run all the time not just when defroster is on if it was sending a false high temp signal to the ecu. The two problems are probably unrelated I guess.

 

The e fan is on whenever the compressor is on I'm pretty sure, and maybe it's on whenever there is a certain amount of pressure in the system.

 

AC acts like a dehumidifier, so carmakers set the AC compressor to come on with Defrost (dry air helps clear the glass better than moist air).

Electric fan is a condenser fan and runs whenever the compressor is engaged. The compressor should cycle off and on periodically, since the evaporator temperature should not change much.

 

Well I guess there might be an issue with one of the switches and my compressor must be running steady also. Never checked just could hear the fan running. Looking back I think the compressor was unplugged when I got the thing. That's probably why. Thanks guys

 

also check your AC relay and Fan relay

 

Sounds normal to me. Any time the AC or defrost is on, the electric fan will be also be on. That's the way mine has always been, even when the compressor is unplugged.