2004 XC70 AC fan stays on after stopping engine

EmperorWatcher · Post by **EmperorWatcher** » 14 Jul 2014, 17:50

I'm having to pull the fuse in order to turn off the fan. Mechanic suggested faulty relay, but I can't identify one that is specifically for the fan.

I switched out the one designated AC Clutch, with no change.

Is there another relay I need to check or is this a different problem?

Post by **abscate** » 15 Jul 2014, 04:31

Is it the blower fan or the engine fan that is staying on? These are both different than the AC clutch and have different fuses.

Volvo manuals are all downloadable so you might want to check your model manual for relay locations for the appropriate fan. I'll check my 2005 this morning.

Post by **chrism** » 15 Jul 2014, 07:34

How long does it run after the engine is shut off? Indefinitely?

Post by **regent** » 15 Jul 2014, 08:50

The AC blower afterblow is a programmable value.
There is also a function of the CCModule that activates it on High for a few minutes to prevent moisture build-up in the cabin when the car is parked in warm and humid weather.

Look here for electrical: http://www.volvowiringdiagrams.com/volv ... agrams.pdf

Post by **abscate** » 15 Jul 2014, 08:52

On ECC, the AC blower also comes on up to 60 minutes after shut down of car to dry the AC evaporator to enhance lifetime. I think this came in 1999+ models

Post by **regent** » 15 Jul 2014, 08:54

Mine has a Manual Climate CTRL and has that as a standard feature also.

Post by **regent** » 15 Jul 2014, 09:08

On another note, there is no designated relay for the AC blower; it has its own standalone electronic speed control unit (some call it 'the blower resistor'), which is controlled by the CCM. If you have to pull a fuse to kill the fan, then it is possible that your 'blower resistor' may be shot (shorted) thus keeping the blower powered on. This will generate a CCM code though.

EmperorWatcher · Post by **EmperorWatcher** » 15 Jul 2014, 11:44

We've been having unusually hot weather, so the AC is getting a lot of exercise. I suspected that the AC fan might be staying on as a system function, but it didn't turn off after 5-10 minutes when I let it stay running (key off). I also had a dead battery one morning, which I'm guessing was the result of this malfunction.

After pulling the fuse, and reinserting it, hours later, the AC fan will start. I understand there is a "magnetic resistor" or power supply that can go bad with the result of leaving the fan on as well.

I'm fearing that this is a "deep" repair, or am I fortunate to not have to remove anything too much to get at that part?

Thanks for helping me identify this issue!

Post by **regent** » 15 Jul 2014, 12:33

First check for codes to make sure it is the blower control module and not the Climate Control Module that has gone bad. Or pull the fuse that powers the Climate Control Module only. There is another fuse sending +12 V staraight to the blower, so if the blower control module is shorted, then the blower will stay ON forever, regardless of the Climate CTRL Module status.

The blower control module is the usual offender; to replace it you need to remove the blower - the 'thing' is inside the shroud - remember everything on our cars has been designed for ease of access

EmperorWatcher · Post by **EmperorWatcher** » 15 Jul 2014, 17:09

I will need to have my mechanic check for codes. I don't have that gear.

I'm not sure what I will learn if I remove the fuse that controls the CCM . The fuse I have been pulling is the 30A one for the blower. At this point, my money is on needing to replace that blower resistor.

How much of the car will I need to dis-assemble to get at that thing? I've seen pictures of it neatly nestling inside the blower housing. I hadn't been aware before, that the Swedes have such a perverse sense of humor.