406 coupe v6 no heat but fan blower fine

wnkxr02 · Post by **wnkxr02** » 12 Jan 2010, 21:47

I need help I have an s reg pug 406 coupe v6 3litre. The heater fan itself works and so do the speeds and can turn it off, but there is only cold temperature, it was left running for 2 hrs and ever ever so slightly went from stone cold. Any ideas ? Could it b the heater resistor or is there other things that would only affect the temperature of what it's blowing out?

Post by **xantia_v6** » 14 Jan 2010, 06:55

I don't know the 406, but assume it is not too different to a Xantia. Behind the engine, there will be a pair of hoses taking coolant to and from the heater matrix. Check that these are getting hot. If not, you have a blockage or an airlock.
The actual control of the air temperatureis controlled by an ECU which drives a stepper-motor, which operates a flap via some plastic gears. On the Xantia, these plastic gears sometimes break, leaving the temperature stuck wherever it is. You may be able to hear the stepper motor whirr briefly after moving the temperature control from one end to the other (if the car is not too cold).
On the Xantia these plastic gears can be seen (and maybe replaced) by removing the ashtray, heater controls etc, but not a nice job.

wnkxr02 · Post by **wnkxr02** » 14 Jan 2010, 13:36

I don't think the temp is stuck where it is as if we pit the air con on it's goes freezing cold like it should. So there us temperature change, just no warm heat. Could it still b the same things? Possible blockages?

Xaccers · Post by **Xaccers** » 14 Jan 2010, 14:59

wnkxr02 wrote:I don't think the temp is stuck where it is as if we pit the air con on it's goes freezing cold like it should. So there us temperature change, just no warm heat. Could it still b the same things? Possible blockages?

That's a physical reaction though not controlled by the climate ECU.
A/C will reduce the temperature of air passing over it.
It's not a case of the climate ECU closing the flap to the heater matrix more when you turn on the A/C.

With a working system and heating on full, turning the A/C on will reduce the temperature of the hot air slightly, but the stepper motor wouldn't have moved.