No heat in cabin

[studley07]

1990 CQ 20 v. Have perfectly good thermostat and all hoses to and from rad all good, hoses to heater matrix all good too but just not getting any heat into the car, heat set at max, fan flat out and direction set correctly. Any ideas where I should be looking to get this working as it is starting to become the wrong time of year not to get any heat in the car especially as it's my daily runner too.

[newsh]

Have you bled the heater matrix hose where it goes through the bulkhead?
If so then probably..
The foam on your heater box flaps has all fallen off.
Or
The heater matrix is blocked with sludge.

Might be time to pull the dash out and replace the matrix and re-cover the flaps.

[Bowie69]

Either that or the cable from the controls has come adrift.

[newsh]

Either rather or the cable from the controls has come adrift.

True

[steve briance]

Does any heat at all get into the cabin?

My heater is not so effective at getting heat out of the dashboard vents and i put it down to the foam flap issue (there were enough bits being blown out onto the seats!) I do however get heat but it just leaks out of windscreen vents mainly and all the other vents a little but there IS heat.

If you have absolutely nothing, it must be a matrix issue - at least try flushing and bleeding before tackling the dashboard...

[studley07]

Nice one thanks for reply. really didnt fancy pulling the dash out. Have bought some rad flush and intend to take of the hose going in to the bulk head attach a clear hose and take off the outlet hose and attach a hose to drain into a drum and flush it out with a low pressure power hose.

[steve briance]

When you come to bleed it, you may well find the handy bleeding screw totally seized up.

I read the following on this forum ages ago; a top sounding tip that you could do if your screw is stuck...

Sounds a bit extreme but, pull the hose off which has the bleed screw and then drill a tiny hole in the pipe. The idea is that if you have for example 25-30mm of pipe inside the hose when on, the hole is in the pipe in such a place that clamped up it wont leak but... Pull back hose 15mm or so till you reveal the hole and allow air to escape but without pulling the hose right off and letting all the coolant escape.

Once the air has gone and you have a steady trickle of coolant : consider it bled and push the hose back on and clamp up.

Its important to make sure the hole is engine side of clamp to be sure it won't leak or, if you are tight on space; directly under the clamp...

1.5-2mm hole will do it.

[studley07]

That's great. Bleed screw is tight and didn't want to snap it. I used a 13 mil 12 spline 1/4 inch drive socket and alot of WD but will do what you have suggested instead. Nice one thanks

[Tractor Dave]

I've never had an issue bleeding mine if you remove the reservoir screws and lift it up high with cap off and engine running
Drilling into a hose 25+ years old seems a recipe for disaster

[newsh]

To bleed the heater matrix I just pull the hose back till there’s a little gap then push it back on when coolant comes out.
When topping up the header tank I keep squeezing the top hose until it stops burping.

[Bowie69]

Never need to bleed mine, once the engine gets up to temp it burps and I top it up and job done.

[gmac78]

Sorry to hijack this thread but also having a heater issue, I think??

I'm starting to think my heater is not as hot as it used too be. System has been bled several times, header tank topped up, heater control cables are all intact, however it just doesn't feel that hot.

One thing I've noticed it that the coolant temp going into the matrix is around 70-75 DegC with a drop of around 10degC on the return hose(laser gun used) even when the engine temp is reading around 87-90 on VCDS. The large hose going on to the top of the radiator is similar to VCDS values. Should the matrix inlet not be the same temp as what the engine is at? The thermostat seems to work correctly, ranging between 87-90 on normal driving, the dash gauge shows the same values.

Another thing, if I flick the heat control from cold to hot I hear the flap make a tinny kind of noise as it comes to rest against it's stop. Would this indicate that foam has come away and not cushioning the flap? I'm not exactly sure what the flap/foam arrangement is??

The same heat and flow comes out of all vents, regardless of positioning, it just doesn't feel as hot as it used to be.

Cheers chaps

[Bowie69]

Your flap foam has gone.

[gmac78]

Your flap foam has gone.

Lovely, another fine job to be getting on with!!!!
Cheers

[newsh]

Audi decided it was a good idea to have some large holes in the flaps then cover them with the same kind of foam they used in the door cards and headlining that turns to mush after 15-20 years. So yeah when the foam falls off you get about 50/50 cold and hot air mixed when the lever is set to hot.