Heating problem, only cold air-blast - Davia A/C car

[dpehlivanov]

Hi, guys,
Sorry for the 3rd topic with question, but i have a heating problem. The car has an aftermarket Davia A/C, i bought it with the A/C installed and working. But now the weather is getting cold and i've noticed a heating problem. When i turn on the heating on a warm temp it blows warm only 1-2 minutes, maybe just to take out the warm air from the engine, then it stops blowing. When i turn on a cold temp it starts blowing again, with two words - the heating works only on a cold temp. The cooling system is ok. The mechanic told me it could be from the resistors of the AC or something like that...

[Billwill]

Is your fan blowing strongly on all speed settings but you are not getting any hot air in?

If so, you may have a blocked heater core, pipes connected to heater core wrong way around or you have air in the system or the water valve is stuck in the closed position.

If the fan is not blowing on some speed settings then you need a new fan resistor block.

[Grrrmachine]

It may be a heater core blockage but could also be the heater valve, which is an electric unit connected to the temp control switch. This can get gunked up if you never change the coolant, blocking it open or closed.

http://www.e30zone.net/e30zonewiki/inde ... oubleshoot

[Brianmoooore]

If the fan is working correctly, the first thing to check is that the heater hoses are connected the right way around.

[dpehlivanov]

Still can't find the problem. The hoses are connected in the right way, cooling system is ok, heater valve and radiator are ok, because when i disconnect the heater valve wires (when it should be open) the heater works normal and it blows warm and everything is ok. When i connect the valve it stops and the heater works only on cold, it doesn't blow warm anymore. Any ideas?

[clipper]

That would suggest to me that there's something wrong with the temp control selector which is meaning that the valve is closing due to the signal sent, in theory, only in the "fully cold" position.

This temp selector is not connected electrically to your AC system (only via a connecting rod that piggy backs onto the lever that operates the hot air deflector flap in the heater box).

From my knowledge the diavia A/C system should sense (through this mechanical link) if the temp selector is on fully cold setting or not in order to determine whether to blow cold(ish) air into the car or not when swithed on. The system however does not and cannot interfere with or influence the heating system which is totally independent.