I have a 2007 XC70 wagon with 149K miles that overheated in a Wash DC garage last week. After the local shop tried 2 replacement used fan assemblies and neither worked (it’s questionable if either was the correct model # which is 30749759), I had it towed the 100 miles back home up here in Lancaster PA where I’ve been troubleshooting it. The battery was also dead (bad cell, coincidental apparently) and has been replaced. I ordered a used fan assembly from LKQ (they’re great btw) off a 2006 Volvo S60 that had 85K miles so figured that should be ok – the part was “tested” and is under warranty from LKQ. I had first tested the power and control cable from the ECM (car runs fine otherwise by the way) and measured around 14 volts power running and various lower voltages for the purple control wire, varying from 0.5v up to as much as 4v. I let the car run at least 20-25 mins until it reached mid-temp range (did not go beyond that while just idling in the garage - maybe we should let it run longer?) and during that time the fan would not start (it was connected of course but not yet installed, laying on top of the engine.) We cycled the A/C on and off and no fan start either. We did check for cold air -- not the coldest but after shutting all but one damper on the dashboard, cold air definitely coming out w/ A/C on but I didn’t want to run that too long to avoid A/C overpressure. The first time I checked the control wire when toggling the A/C, the voltage dropped quickly from about 4v down to about 1v. So all indications seem to point to the fan module again not working which is hard to believe especially since that would be 3 bad used fans on top of my original one that had definitely initially failed, leading to the brief overheating last week. Any suggestions for next steps appreciated, thanks.

 

A new fan. Used electrical parts are never a sure thing.

 

thanks - certainly have considered that but given the mileage (yes, just getting broken in at 150K), trying to avoid spending the $350 to $400 for a new fan assembly -- any other ideas out there appreciated, thanks

UPDATE.... I've had the radiator fan issue diagnosed by my Volvo specialist shop and they've confirmed that the ECM computer requires repair/re-programming at about $800 plus some additional labor. He agreed that installing a simple 4- or 5-pin relay-controlled toggle switch would work. I've put together the wiring setup (see http://www.hournineracecraft.com/relay2.html) and I've confirmed the relay works using a voltmeter but I've been unable to get the fan to turn on. My assumption is that the Bosch relay that is integral to the back of the fan motor assembly is still looking for that ECM control signal.
Ques: Has anyone successfully set up a manual control switch for the same or similar Volvo fan assembly? Do I perhaps have to consider installing a "generic fan" without the embedded Bosch relay (original Volvo radiator fan assembly part # Part Number: 30749759 such as at https://www.volvopartswebstore.com/p...gaAq1GEALw_wcB)
Thanks

 

I have the same issue with my 2010 Volvo C30. Put in a new fan assembly which includes the Bosch relay. Fan still never comes on and car overheats during stop and go traffic. Voltage on the signal wire at the fan connector seems to vary between .25 volts at engine start (cold) and .19-.25 volts when engine hot. Shutting off the engine when hot......signal wire voltage is 0.
A/C on full the whole time of testing.....
I suspect a replacement fan was not required.....the problem seems to be the voltage from the signal wire to the relay is not sufficient to command the fan to turn on.
I wonder if there is a problematic temperature sensor involved, however the instrument cluster temperature gauge seems to display accurate temperature.
How did you resolve your case?