Heating Issue

[gripper]

I have a problem with the heating in my coupe
I have warm (not hot) air coming from the vents ! Have replaced Radiator, Thermo switch,Thermostat,Water pump,Heater matrix,Expansion bottle several hoses and bleed hose leading from matrix !
Absolutely no leaks and has been bled several times ! Heating is mediocre at best
Fans (stage 1 & 2) are kicking in at around 88c.
My mechanic is stumped and can only suggest it may need a Thermostat that has a higher temp range as I'm sure fans are not supposed to kick in till the 90 +1 and +2 stage.

Any help would be greatly appreciated

[Nuvo]

Perhaps one of the vent flaps is sticking?
Check the bowden cables for any obstruction or maybe one of the tags at the base of the heater box is either broken or has popped off?

[Error404]

[gripper]

I did consider this, maybe I should have been more specific in my post !
Footwell, vents and dash all have the same heat output.
I thought the flaps and Bowden cables only controlled heat direction not tempreture

[Nuvo]

The middle heater knob controls a large flap that sits directly in front of the matrix, this is how the amount of heat radiated is regulated, the blower controls the flow of course.

[Nuvo]

It might also be worth checking to see that the large "tuba" ducting is properly fitted and isn't leaking air.

[Error404]

yup Rob is right there is a large flap that controls airflow across the matrix (hot) or bypasses it (cold). IIRC the cable lever on the heaterbox for this flap is accessible behind the aux gauges. Rusty might be able to help you out with a pic as he had his out recently

[Greg_S]

Yeah Id check the flap. Mine jumped a couple of teeth years back, re adjusted it and its been fine since

[gripper]

I am able to move the centre knob from hot to cold and vice versa smoothly and I can actually hear the noise and feel it as it moves the flap.
Set fully to cold it blows cold but set fully to hot it blows warm !
Will check the tuba ducting

I don't really want to have the dash out again !!

[shaun5]

How about feeling how hot the pipes are that go into the bulkhead (to feed the heater matrix) Maybe take them of when the engine is hot and measure the temperature

[Rusty]

If the foam has fallen apart, it'll not work properly

Fan kicking in at the wrong temps could be air in the system or a leak to atmosphere preventing pressurisation.

[s2_wot]

Can you pressure test the circuit as per 19-14 of the service manual?

http://www.s2-audi.co.uk/workshop/aan/aan.pdf

[ManiacuV6]

double post

[ManiacuV6]

This kind of heating system has only a weak spot : the heater matrix gets blocked in time . My bet is the heater matrix. Not an easy job but it can be done.




Did you use a NEW heater matrix ?

[newsh]

Yeah, I'm thinking foam fallen off the flap and/or a blocked matrix.. And this applies to my car as well!! Not getting much heat out of my heater either. I have a non -aircon heater unit ready to go into mine but I need to strip it to replace the matrix and the foam first.

Just on a side note, one of the coldest drives I've ever had was at night in the middle of winter back to Surrey from MRC after forgetting to put the top back on the fuse box