Ask Honest John

Honest John Ask Honest John » Heater blows hot when moving and cold when still.
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks

Heater blows hot when moving and cold when still.

I've got a VW Transporter T5 1.9tdi and it's just started blowing cold air when it's sitting idling, but when I bring the revs up or drive it blows hot. When I slow down or stop at the traffic lights it goes back to blowing cold air.

The temp gauge sits half way like it always has done and its not the heater matrix because I flushed it out and it was fine. I am thinking water pump but I'm not 100% sure.

Asked on 21 November 2011 by jonnyboy16v

Answered by Alan Ross
Not sure why you think water pump. Would suggest that you re check your coolant level to make sure it is correct. Also what temp is the engine running at?

Also check the connections leading to the heater matrix, if there is a tap/switch (connection from the engine block) is that fully operational.

You may also need to check that the flaps behind the matrix are diverting correctly.

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide
Similar questions
The temperature gauge oscillates between optimal and maximum on my 2001 Ford Mondeo 1.8 petrol. My heater doesn't work well either. Most of the time it blows cold air and occasionally gives a burst of...
I'm having problems with my girlfriends's Ka - the heater has stopped working completely. It dosent work at all on any number, I have checked all the fuses - all fine. All I can find is info on how to...
I have a problem with the heater fan blower on my 2004 Vectra SRI. The blower only works on the high setting - 4. It does not work on 1 to 3. How do i locate the resister for this model.