Need help. I just put back the AC system in my 2005 evolution and a full size radiator from mishimoto. After putting coolant in and firing it up. I noticed the radiator fan was on already and the car was still cold being started for not even a minute. With ignition on the radiator fan doesn't come on only as soon as it's started. My AC compressor has no belt on it yet and no freon. But I wanted to check if the condenser fan works when the ac button is pressed and the fan does not come on. Is that normal or is there an issue with that. I tried a brand new oem Fan Control Module thinking that's the problem but it's not. Fan still comes on right away when started. I checked all fuses for ac and they are good. Didn't check the relay for it because I don't have a multimeter at the moment. What else could the problem be ? Possible coolant temp sensor in the thermostat housing? Or the relay for the fan? Any help is appreciated.

 

Coolant temp sensor, or the tune is set to always run the fan when the engine is on.

 

Thanks I am actually in the process of downloading aem infinity now to see that. Car previously had a half radiator. Thinking that could be the issue. Is it simple to shut off via aem

 

As I recall, the fan relay is always closed when the ignition switch is in the run position. The ECU is what turns on the fan. Inputs to the ECU are: speed sensor (I doubt this is your problem's cause), AC switch and coolant sensor. So, possibilities that I can think of are bad coolant sensor or the ECU thinking the AC is always on. The coolant sensor is a variable resistor that has higher resistance when cold. So, for the fan to run resistance would have to be low.

 

I've never done any AEM stuff. All I know is that with a stock ECU its possible to make the fan run constantly when the engine is running if you make the right tweaks in the ROM.

 

Ac compressor is connected to the harness but there is no belt on it and the switch inside to control is off. And fun still is on. I have a feeling it has something to do with the aem. I am going to have my tuner check this problem out. I guess on a good note the car won't overheat but possibly can burn the fan out and which I would have to remove the whole radiator to replace the slim fan again which I just installed.