no heat in car

[mallyg]

My car is an M reg xantia 1.8i. I have a problem in that there is no warm air being blown into the car. I have checked the cooling system having also had a problem with the car overheating. There is a pipe that comes off the side of the thermostat housing that leads to the 90 degree plastic elbow bend and the bleed valve and then into the bulkhead which I assume then goes to the heater matrix. I have checked this pipe and the pipe gets hot between the thermostat and up to the bleed valve but after the bleed valve is cold. Is the 90 degree plastic connector where the bleed valve is likely to be blocked. I have bled the cooling system using the "header tank" method so i don't think there is any air in the system. thanks in advance for any light anyone can shed on this problem.

[Peter.N.]

It sounds as though either you heater matrix is blocked or its full of air. Try disconnecting the return pipe with the engine running, if you get no water from the heater end the core is probably blocked, although its unusual for them to block completely, but this should get the air out if this is the problem.

[jeremy]

The Xantia I think has an air blending heater - which means that the matrix is hot all the time as it doesn't have a water valve. The heat output is controlled by flaps - so are they all operating properly?

[Mandrake]

The Xantia I think has an air blending heater - which means that the matrix is hot all the time as it doesn't have a water valve. The heat output is controlled by flaps - so are they all operating properly?

Yep, the Xantia matrix is hot all the time, no water valves...which means once the engine is up to temperature the entire run of heater hose should be hot....

The very early (only 1993 ?) models have manual control over the air blending flap - whether its a direct cable or a potentiometer which controls a motor I'm not sure. These can be recognised by no temperature figures being next to the slider, just a graduation... (my mums 1993 1.9TD is like this)

Later models (1994 onwards ?) have a cabin temperature sensor next to the clock (with a small fan that draws the cabin air in past the sensor) and the temperature slider has actual temperature figures beside it - this is a fully automatic system which has a motor driven air blending flap which it controls as it sees fit to reach the target temperature.

The flap can be quite slow to respond to movement of the sliders - up to 10 seconds depending on the situation. Setting the control fully up or fully down (the red or blue mark) will force the flap into the fully cold or fully hot position regardless of what the temperature sensor is picking up. (After up to a 10 second delay)

Furthermore on these later models with temperature regulation the fans and the flap control only function when the engine is running... turning on the key is not enough.

If you set the fan speed to minimum (NOT off) and move the slider to fully cold, wait a while, then fully hot and wait a while you should be able to hear a strange noise coming from behind the dash which is the motors that operate the flap...

If the car has the imfamous ignition key burnt contacts problem which affects the cabin blower motors, it can also affect the operation of the air flap control system...as the fan speeds and air flap are all controlled by the same controller...

From the symptoms in the first message I'd have to say its more likely an air lock or blockage in the matrix though - that whole run of pipe should be hot...

Regards,
Simon

[wonderd]

First check to see if the bleeder right at the end of the hoses going into the firewall, open it all the way and watch for water coming out.
if there is an air pocket it will come out and a few seconds after you open it, water will come out.
Second, if no water come out of there, open the two hoses connection to the firewall, insert a garden hose in one of them and turn on the water on high pressure, if the matrix is clogged, the water will release it, try both ways until you get a big amount of water coming out the other hose.
Yesterday it took me 15 minutes to clean the matrix that way and replace all the water in cooling system, now there is a wonderful heat in my car.
good luck.