Audi A4 heater problems

Sdoody92

Hi, I have a 2006 Audi A4 1.9tdi. The heating in the car isn't working, only blows cool or cold air, the temp of the car does go to 90degrees but it take nearly a hour or so of driving to get to 90... The two coolent pipes at the back of the engine going to the heater matrix have been looked at, one is warm and hot but the other is cold any idea what may be the problem

biko

Sounds like thermostat is stuck open.
I take it you checked coolant level?

Bruthal

If the heater works with the car left parked in the driveway and ticking over until the engine is up to temperature, but not when driving, then the thermostat is probably stuck open alright, once its not short of coolant.

Sdoody92

Ya coolent level is ok.... would the thermostat cause the heaters not to work?

biko

It would cause the air blown from the fans inside cabin to not be warm yes.

In short, if the fans inside car blow tepid/cool air when they should blow warm/hot air this means two things - either there is no coolant to carry the heat from the engine to the core in your dashboard, or the coolant isn't warm enough.

ECG explains it quite well I think

https://www.youtube.com/watch?v=PGkSfPbGr3Y

Sdoody92

Update** so today I was looking around the car... I noticed that my fan would come on anytime I have the fans on in the car.. is this normal? Also I noticed if I leave the heater fans turned off for a few mins when I turn them on I get about 3 or 4 seconds of nice warm air then goes cold again...

Bruthal

Heater cores can also clog up. Or the vane which directs the air from the hot or cold selected, can be stuck. The little bit of warm air at first, suggests this is working.

Blocked cores can cause the initial warm air then cold.

Did the radiator fan come on if the car is left idling?

If the radiator fan came on while the car is parked, that`s normal, but does not mean the stat is certainly ok. When driving, air is forced through the radiator at a high rate by the cars motion. So much so that the coolant would be cooled too much, so the stat closes when the coolant cools a bit, then re-opens to let it flow through radiator again when it starts to get hotter again, and cycles like that.

If the car is parked, (with no strong wind blowing into radiator) and idling, the coolant will come up to temperature, and the fan kicks in to cause airflow through the radiator to cool coolant and therefore the engine.

So with the car parked up, and if the radiator fan is coming on and off, the heater should work even with a stuck open stat. If it doesnt, there is likely another problem such as clogged heater core, airlock, stuck air vane etc.

Car99

If its not the thermostat i'd put my money on the heater matrix being blocked as I had that issue on my last A4 B5 after bleeding numerous times and replacing the thermostat I had to change the heater matrix in the end , pig of a job as the dash had to come out but on the the B6/B7 I think you can do it with the dash in.

John T Carroll

Car99 wrote: »

If its not the thermostat i'd put my money on the heater matrix being blocked as I had that issue on my last A4 B5 after bleeding numerous times and replacing the thermostat I had to change the heater matrix in the end , pig of a job as the dash had to come out but on the the B6/B7 I think you can do it with the dash in.

Its very easy to check if the thermostat is stuck/passing, at any stage before the gauge reaches 90C (which is actually only 75C in reality) feel the top hose just before it enters the rad, it should be almost stone cold, I very occasionally check mine (VWs) . Re the blocked heater matrix, could the two hoses be removed at the engine side? and tested/cleared by back flushing. I wouldnt be too happy with a blocked heater matrix as apart from its heating function it also acts as the coolant bypass circuit until the thermostat starts opening, as far as I know.