I have a 2006 XC70. Has a lot of miles but in great shape. Like 240K. Yesterday my temp gauge stopped working. (Before that the temp was reading normal.) When I got home I noticed the radiator fan was on full blast! Crazy! It shuts off when I shut the motor off but otherwise stays on crazy!

We replaced the temperature sensor and thermostat with thermostat housing but no luck. The gauge still doesn't work and the fan still goes crazy.

From what we've read it could still be the : Control motor?, the fan/ fan motor? control unit? fan ECU? The cluster? Bad wire??
(forgive me for not knowing the exact names, this was passed on to me through my brother who is working on it. He's not a Volvo specialist though so any help or guidance would be very much appreciated.

Also, as an aside, I have a 2003 XC-70 where the axel died but has good parts. Can some of these parts be transferred? Like what about the ECU? etc..

Anyway, I'm hoping someone looks at this and says "Oh yeah its THIS!" Thanks in advance!

Best,
Doug

 

If I recall, the 06 model is new enough that the temperature sending unit is part of the thermostat assembly.

https://www.rockauto.com/en/moreinfo...433144&jsn=381

The wiring up to the sending unit runs along the back of the alternator down into a nest at the lower portion of the block. Test for voltage on the wires before getting too far. The resistance in the sending unit is what runs the gauge.

Also, see if you can read the engine temperature through the engine computer data. It might just be the gauge unit on the dash. You have to narrow down the problem.

Sounds to me like the wiring might be grounding on the block sending a full signal simulating a hot engine, thus, the cooling fan running all the time.

 

also, did you check the fan's relay?