ACC not heating unless driving uphill

[gtrombone]

Hi all,

I have a new problem which I hope will be easy to diagnose:

I’ve recently noticed the heating in the car has been inconsistent. It blows fine but the air is sometimes air temp (it’s winter) and sometimes heated.

I had a long drive yesterday (600km) and the air temp was below 10C all the way so I had a good chance to observe it.

What I discovered is that the air was blowing at outside air temperature UNLESS I was driving up a steep enough hill.

That is, heating was running fine uphill only.

I’ve tried a few tests with cold air (A/C) but not recently. It also seemed inconsistent.

Is there a switch or servo somewhere which would explain this problem? Which parts would I need to solve it please?

Many thanks, Gus

[gtrombone]

PS I ran the acc self diagnostic test (press auto and off simultaneously) and it just showed a “0” during the testing and returned to usual operation.

[sgould]

What does the outside air temperature show up as on the dash display?  If the sensor is sending the wrong info, the aircon could be switched off automatically.  The aircon recalibration test doesn't check for temp sensors sending the wrong info. It will only notice if they are missing!i think.

[gtrombone]

Hi,

Thanks for the suggestion sgould, there was nothing wrong with the temp reading.

The repair was a solenoid which had ceased operating. The explanation for heat working when driving up hills was that there was enough pressure in the system to force the valve open.

Many thanks!

[sgould]

Thanks for reporting back.  That was a strange fault.