1999 V70 Ventilation Fan Climate Control fault

[Neil123456]

My cabin ventilation fan stopped blowing a few days ago. I noticed 20 seconds of flashing recirc and A/C off lights on starting the engine.

A first pass through google showed me how to remove the glovebox inner and airbag cover to access the fan, which I didn't fancy as a first shot, airbag's'n'all.

A second effort at google came up with blowing the dust out of the cabin temperature sensor next to the switches. After this, the fan worked. Next outing I had no flashing lights, full fan function, manual full blast, auto low speed until the engine warmed up and then faster to warm the cabin. However, I celebrated too soon.

Next outing, and every time since, I've had no fan and the 20s flashing lights again.

I've inspected the cabin temperature sensor through the grille with a torch, and there's no visible dust, and its fan spins. The fact that the ventilation fan worked again after blowing the dust suggests to me that it's not that that's faulty, but I might be wrong. The rest of the ECC seems to work, when I change air settings I can hear dampers whirring.

I've tried to get the temp sensor module out, having ejected the radio and ECC, but though I can see the back of it with a dentist's mirror, I don't see any way I can navigate my hand to the plastic catch. Is there some knack to popping this out? Or do I have to make a cranked, mirrored, tool? I am an experienced electronic engineer, so should know what to make of it if it's in my hand.

I could get the codes read. I have a backstreet independent, specialising in Volvos, quite close to me, and several other small garages. What would I expect to pay for a read at either? Would that diagnose things down to sensor or fan level? If so, it may be worth getting done.

[warninglight]

I've had that before and it was the blower fan itself. I got through a second one before realising an old pollen filter was stopping air getting to the fan and making it overheat.

I have a fan on my breaker here which works well and quietly. It's the ECC controls with the slider for fan speed. Not sure if the fan is the same on the more basic air con setup but happy to compare part numbers.

Changing it isn't too hard to do, disconnect the battery half an hour before starting the job to make the airbag safe (not all models have an airbag here) and it's pretty self explanatory from there on with some torx screwdriver bits.

[Neil123456]

Well ... it's all working again, for the moment.

Given the misting weather at the moment, a working blower is a safety essential, so I dropped the parcel shelf, and wired the fan motor to a fused cigarette lighter plug, so it comes on full with the ignition. It worked fine.

Finally managed to find the catches to release the cabin sensor. There are two, on the body, opposite each other, about half way along. It's fine, the motor spins and the thermistor reads between 14kohms in a 15C garage and 7kohms when I breathe on it. Tugged about on the thermistor wires a bit trying to provoke an intermittent, it was solid.

So, put everything back together and it just works, is that good news or bad news? I guess I'll have to wait for the intermittent to reappear, wherever it is!

[warninglight]

Sounds likely that it'll be the controls on the dashboard, in that case!

[jimka]

I have a ECC unit from a 98 V70 if you need one.

£15 + post. Can post a picture - just send me a PM

Jim

[Neil123456]

Hi Jim,

My fault has now returned, first with intermittent damper failure, and now with that and fan failure again. As I know the fan works, and can hear the dampers moving intermittently, I suspect it is controls. I'm of a mind to rip out the CCU and install some manual switches, but if you still have the CCU you mentioned, I might be tempted to try swapping units.

Would you send me a picture please so I can check the exact model.

Are there any ways I could verify whether it is the CCU or not?

Neil

[NI_Volvo_Nut]

I have a good unit in the V70 I'm breaking, drop me a PM if you need it.