Mend > Cars

How do I diagnose a faulty heater matrix in my VW Passat?

I have no hot air in my car, which has been SORN for 3 years whilst I worked abroad

I have changed the thermostat and water pump and the cooling system seems to be working OK.

Still no hot air. There is some hot air initially when the car is warming up, but when the blower is on only cold air comes through.

Is the fault the heater matrix or could there be something else?

Any help appreciated

Grampus
November 2007

VW VW Passat Vehicles, Cars Heater Hot Air

try bleeding the coolant system again as you have had pipes off the water runs out and the system fills with air it may just need bleeding just like radiators do in a house when replaced hint hint,,,, one way to bleed the the coolant system is by a bleed valve on the one of the heater matrix pipes or simply just pull the pipe off coming out of the matrix, top up the coolant and when the waters through simply replace or tighten

garthy
November 2007

It could be one of the flaps that control air flow into the cabin that is faulty. The air flow positioning motor could be stuck on "cold" or the main flap positioning motor could be stuck.

Take it to a local garage and ask if they have "vag.com" or the bosch diagnostic tools to see what error codes come up. Most places (not vw dealers) will do this for free or a small fee. VW dealers will want £40.00 off you just to tell you how much it will cost.

I believe that a faulty/leaking heater matrix should also show water in the cabin or bad condensation on the windows as a symptom as well.

Matt Slack
November 2007