2001 xc70 radiator fan doesn't cycle

Danpaco · Post by **Danpaco** » 10 Feb 2015, 14:31

I finally got my new to me ride on the road after an epic struggle with the DMV. The car has been parked in my driveway for two weeks and the weather has been cold and snowy.
When I started the car today I noticed the radiator fan was on high and would not cycle to off. The AC is off in the cabin as is the windshield defroster. Any thoughts as to why this is? And where can I start diagnosing this problem?
The fan behaved normally on my test drive and engine compartment inspection three weeks ago.
Thanks
Danpaco

Post by **jimmy57** » 10 Feb 2015, 17:32

If the ect sensor (engine coolant temp) is unplugged, wires broken, mice chewed through wires, etc. then the ECM will run fan at high with key on.

Danpaco · Post by **Danpaco** » 10 Feb 2015, 18:26

Where could I find the ECT?

Danpaco · Post by **Danpaco** » 12 Feb 2015, 06:39

Everything looks good with the ECT wires and connection. Before I start throwing parts at the problem, thermostat,new sensor, etc..., what can I test electrically? What should the resistance value be on the ECT, is there a relay control I can check?
The car runs well, no CEL, no hidden codes, just passed emissions.
I do notice the temp gauge in the cabin is slightly past "12 oclock".
Any help would be appreciated.
Danpaco

Post by **regent** » 12 Feb 2015, 07:58

Please take a look at this thread:
Diy 1998 v70 ect engine coolant temp sensor replacement

Post by **DGM** » 12 Feb 2015, 10:08

Also this thread may help;

https://www.matthewsvolvosite.com/forums ... =9&t=50104

Post by **xHeart** » 12 Feb 2015, 14:25

Danpaco wrote: ...
I do notice the temp gauge in the cabin is slightly past "12 o'clock".

I had same issue; temp needle taking longer to reach 12 and then visibly staying pass 12.
The engine hood over the passenger section will smell hot, and high-temp at touch. The protective cover over the spark plug extremely hot. But the car ran fine.

Changed thermostat around 134,000 miles with Wahler/Volvo. It was original.
I have serviced and replaced all heating and cooling parts in past 18 months, except radiator.