Heating Blowing Hot OR Cold

[dannosail]

I've got a 325i with Air Con, which works however, when I try to adjust the blower air temperature with the Air Con off it just stays cold until the dial is hard over to the right at which point it goes to full heat.

There's no inbetween temperature. The bowden cable seems to be ok, I'm wondering if it's the valve, I've heard they can get stuck - anybody help.

Cheers.

[Nelly]

As you said, theres a one way valve in the heater matrix that can get stuck also, if you get a slight clicking noise when heat is selected, check the matrix flow and return pipes in the engine bay = from the rear of the head to the lower connector + from the header tank / thermostate housing to the top connector is the correct way round.

Not much help but, you never know?

Neil.

[DanThe]

Could be the valve, could also be the matrix partially blocked.
The valve should open with the dial pointing at about 9 'o' clock

[Brianmoooore]

The electric valve only cuts off the water flow through the heater matrix when the dial is set to full cold. As soon as the dial is moved a few degrees clockwise the valve switches off and takes no further part in the proceedings.
If you disconnect it electrically, then it makes little difference to the heater. Just a little bit of heat bleeding through when it's supposed to be cold.
Actual temperature from the heater is controlled by a blending flap on the end of the bowden cable.

[DanThe]

You ought to check the temp of your pipes first, as Nelly describes the bottom pipe feeds the matrix and the top is the outlet, with the heat on but fan off check the temp of both pipes

[dannosail]

The electric valve only cuts off the water flow through the heater matrix when the dial is set to full cold.

Is this the same for cars with Air Con? That means you would have heating and cooling going on at the same time unless temp gauge was fully cold - which could make sense as the Air con and heating are separate matrices but this isn't a very sophisticated design.

Nelly, Dan, I'll check the pipes, as I say I think the bowden cable is working ok but it is probably worth checking if what Brian says is correct (i.e. always! ) to see if there is no mixing of air going on to give me a medium heat and not just full heatwave!