Heater blowing cold

[davos]

Hi, the interior blower / heater in my XC90 D5 (55 plate) is acting up. Just woundered if anyone had, had the same fault or if their had been any previous threads about this issue. The problem is when using the heater from cold, it takes for ever to blow constantly hot, probably around 25 - 30 minutes after starting. The fan speed varies slightly and blows fairly warm for maybe 2-3 seconds then cold for a second or two, hence the cabin not warming through quickly enough.
I`ve had this simular fault in other cars, where the speed and heat has a mind of it`s own, and is usualy just a quick fix, a replacement resistor pack. But on the volvo it`s only a minor speed difference, but a constant hot / cold /hot /cold, then 30 mins later it behaves and blows just fine. This does not usualy happen on other makes, when faulty it`s constantly faulty.
Any ideas / fixes, and has anyone had the same prob.
Thank god for the best heated seats ever, -10+

[wolfie308]

Try here....may be same issue

http://www.volvoforums.org.uk/showthread.php?t=108816

[davos]

Cheers for that, hope it`s just something as easy as this, as anything involving me and the volvo usualy ends up costing and a lenghty repair.

[davos]

NO still have a heater with a mind of it`s own, very cold and no real heating in a 12K car, wish it was summer. Tried cleaning the little fan at the back of the heater controls, not realy that badly soiled and has made no difference.
So rang the dealer for so free advice, they told me to try the following:-
Run heater on cold for 10 minutes then gradually build up the temp setting and this would reset the heater computers????? over complicated electrics spring to mind, wot`s wrong with a good oldfasioned cable to open a flap!!

PLEASE HELP

[pdrvolvo]

Originally Posted by davos

NO still have a heater with a mind of it`s own, very cold and no real heating in a 12K car, wish it was summer. Tried cleaning the little fan at the back of the heater controls, not realy that badly soiled and has made no difference.
So rang the dealer for so free advice, they told me to try the following:-
Run heater on cold for 10 minutes then gradually build up the temp setting and this would reset the heater computers????? over complicated electrics spring to mind, wot`s wrong with a good oldfasioned cable to open a flap!!

PLEASE HELP

Not sure if this will help but i used too have an S80 (my 2000) that had a heater fault.the heater would blow hot for a couple of seconds and then cold and than back too hot and so on.Took the car back too volvo under warranty and it required a computer update on the heating system !!!.


peter.

[davos]

Yes sounds like i will have to go back to Harratts, for them to sink the heating system back in!!!, the usual £85 + VAT for the diagnosis. More top notch free coffee for an hour or two, while they plug in their lap top.
Took the side panels off the lower center console, the carpeted bits and could see the half dozen or so motors controling the heater flaps. They were just revolving in a circle from hot to cold settings, without me actually touching the controls!!!! so hot then cold and so on. So for the time been to stop the wife`s bottom lip shaking i have unplugged the motors on hot setting, and all is well Forgot just how good the heater was, will have to replug for the summer. Unless anyone out their has a better fix???
Cheers Davos, Happy new year.

[Ron_XC90]

I assume you have cleaned the temp sensor as in the other thread?

The heater seems to be linked to the outside temperature sensor in the driver side mirror. Is the outside temperature reading correct? This could cause issues if not...

[springbokrugby]

This is linked to a faulty Air Quality Sensor. Very expensive (and tiny) part which sits in the cold air intake underneath the wiper covers. Change that and your problem will more than likely be sorted.

Time to DIY fix, about 20 minutes (allowing for a lot of fiddling if you've not changed this part before.

Cost of part. Over £300 from Volvo. I was lucky and picked a a new (other) part on eBay. Been bought by someone and never fitted. Cost £120 and took 10 minutes to fix. Problem of hot/cold/hot/cold sorted.

[SwissXC90]

As a cheap no-cost option, you can simply disconnect the Air Quality Sensor

This will of course disable the Air Quality function
But some people prefer working heat and do not car about working air quality system.

And it is a simple and no-cost action for you to try. It will at least clearly identify if the AQS is to blame....

[Tannaton]

Originally Posted by springbokrugby

This is linked to a faulty Air Quality Sensor. Very expensive (and tiny) part which sits in the cold air intake underneath the wiper covers. Change that and your problem will more than likely be sorted.

Time to DIY fix, about 20 minutes (allowing for a lot of fiddling if you've not changed this part before.

Cost of part. Over £300 from Volvo. I was lucky and picked a a new (other) part on eBay. Been bought by someone and never fitted. Cost £120 and took 10 minutes to fix. Problem of hot/cold/hot/cold sorted.

I don't think an AQS fault would cause this? The AQS system controls whether fresh air is drawn into the cabin or recirculated air is used - it does not control temperature.

On my 2003 XC90 it's been recording AQS sensor failure for 5 years and the heater works just fine.

I don't fully understand the entire system so I may stand to be corrected but I don't think it's likely to be the OP's issue.

As with most XC90 issues, sensor readings and fault code diagnosis from VIDA is always a good place to start...