XC70: Electrical Climate Control Issue

[zapcity1]

Hi all, I have a problem with the climate control on my '09 XC70 D5.

When starting up, everything works as expected. The blowers push out hot air and the cabin gets up to temp (set at 21-23) in about 10 mins. All as expected.

When the cabin temp is reached, the vents on top of the dash start to pump out cold air (was hot). It appears that the cabin temp then reduces as it definately becomes colder. I can manually reduce the flow of cold air by turning the fan speed down to minimum and manually directing the air, but I still get a cold draft from the dash top vents enough to make it uncomfortabe.

I've run a VIDA diagnostic (I'm no expert in VIDA by the way!!) with the following result (see attachement): -

CEM-B10EA14 - Positive Temperature Coefficient heater - General Electrical Failures - short circuit to open or ground

I know my car has the PTC heater fitted (as confirmed by VIDA), but I thought this was used to supplement the car heating from cold, as it's effectively a high kW heating element. Therefore I can't understand why I'm getting the issue I am. I would have though that if the PTC heater is faulty I would get slow initial heating follwed by normal heating once the conventional system is up to temperature but this is not the case. Once my cabin is up to the set temp., then it starts to blow cold.

This PTC element is buried in the dash (item 29 on attached pic), but I don't know if the error code relates to this or the CEM itself. VIDA gives no instruction on replacing the PTC element either.

I've seen this issue on a couple of older threads on other forums, but not with any resolution.

I have the option to recalibrate the CC, but VIDA doesnt show this as being an issue.

Just wondering if anyone else has seen this issue, or can offer advice before I get the dealer involved. Thanks.