2004 s60 cooling fan runs fast from startup

[quietcoolone]

Recently notice that the engine cooling fan on my 04 S60 2.5t comes on immediately upon startup the engine. It will run for as long as the engine is running. Stays on high speed for a few seconds then to low speed for a few when engine is turned off, then it will shut off on its own. This happens in cold or hot temperatures. The temperature gauge does not go beyond 12 o'clock, check engine light is off. I replaced the fan motor assembly with another from an 05 s60 but that did not fix the problem. Can't seem to find a dedicated fuse or relay so I'm stumped. I know the fan worked at low speeds but now it's at full speed all of the time and I'm concerned that it might burn out..
Can anyone help?
Thanks in advance

[oragex]

Maybe the previous owner bypassed the temp sensor to the fan switch.

[Orca2]

I read a post on here a while back where the wiring to the temperature sensor was routed round the subframe at the front of the car and had chafed through to make the fan think the coolant was hot thus fan ran constantly, might be worth checking that you do not have the same problem.

[quietcoolone]

The fan has 2 thick wires and a single small wire. The red wire goes to a 60 amp fuse under the fuse box in engine compartment, black to ground and small purple to ecm. I figured it must be the signal wire from the ecm or related sensor and decided to disconnect the battery and reset ecm. Waited 3 hours and reconnected the battery, started the car and fan did not run. I then turned on the ac and the fan ran at its normal speed. Turned off ac and soon thereafter the fan stopped. Took the car for a spin and everything was back to normal. Turned car on 3 hours later and the fan did not come on. I will monitor this situation for a few days and report back.

[Brendan W]

If it was the loss of temp sensor I would expect to see the temp warning lamp on and the temp gauge possible registering hot. It's a quick way to test the fan by just disconnecting the sensor. In some cars it will also trigger an engine management light which may take two or three cycles after the disconnect to switch itself off.
The other possibility is the aircon system. I can't recall exactly but low gas pressure might do it. There is a thread here some where about this exact issue.
http://www.volvoforums.org.uk/showth...r+conditioning

[oragex]

Originally Posted by quietcoolone

The fan has 2 thick wires and a single small wire. The red wire goes to a 60 amp fuse under the fuse box in engine compartment, black to ground and small purple to ecm. I figured it must be the signal wire from the ecm or related sensor and decided to disconnect the battery and reset ecm. Waited 3 hours and reconnected the battery, started the car and fan did not run. I then turned on the ac and the fan ran at its normal speed. Turned off ac and soon thereafter the fan stopped. Took the car for a spin and everything was back to normal. Turned car on 3 hours later and the fan did not come on. I will monitor this situation for a few days and report back.

How did you reset the ecm? Just leave the battery off for 3 hours?

[quietcoolone]

Originally Posted by oragex

How did you reset the ecm? Just leave the battery off for 3 hours?

Yes. All I did was disconnect the negative battery terminal for 2 hours and the fan was back to normal. I never got a check engine light and the temperature gauge never went pass 12 but whatever the issue, it has been resolved and working for the past few days.
Btw this situation began after taking her in for a wheel alignment. As soon as the mechanic drove up I could hear the fan was louder than normal. I drove home thinking that it was bc the outdoor temperature had gone up.