Air Con

[diesel-a4]

hey folks so the MOT retest is 2moro and all should be well. Just one thing, me dam air cin isnt working.

Its a 98 A4 1.9 TDi SE 110. The air con is blowing cold air into the cabin and only cold air no matter what setting the air con control unit is at. (the one with the lcd panal)

now i had a look about with my guy who does the work for me and we can see that the pipes going into the heater matix are fooking hot but after that nothing, no hot air just cold

the theromasat has been replaced and the water leak fixed, Engine temp is at at steady 90. i then started to think the acutal control panel was ****** but it changes the speed of the air and which area it blows out off.

thoughts??

 

[Siena]

Blocked heater matrix.

 

[aragorn]

could it be the stepper motor that actully adjusts the hot/cold mix?

If both pipes are roasting it would follow that there is flow thru the matrix, although there could be an airlock?

Its easier to check for a blocked matrix or an airlock though so do that first!

 

[AndyMac]

It's not an MOT fail though, and should be a fairly simple fix. Far simpler than if the A/C system was faulty as that can get expensive.

 

[diesel-a4]

shes blowing warmer than outside air, just hot enough to clear the wind screen but its still cleary cold.

anyone know how i can test the heater matrix myself?

 

[Siena]

shes blowing warmer than outside air, just hot enough to clear the wind screen but its still cleary cold.

anyone know how i can test the heater matrix myself?

Best way to flow test the matrix is to disconnect the 2 pipes - supply and return, and fit hoses to them.

You'll then need to get a funnel of the correct size, fit to the lower pipe / hose, and pour water into it.

Make sure it's flowing ok from the return (top hose / pipe).

If the return's poor, then you'll need to replace the matrix.

One thing, don't be tempted to use high pressure from a pressure washer to try clearing it - I had a client do similar, and the matrix exploded, drenching the interior of the car, and made a bit of a mess.

Cold water supply direct from the tap is ok, though it's hard to determine poor flow, as the pressure from domestic water supply may make the flow appear good, when it may not be the case.

 

[diesel-a4]

i fancey giving thisa go myself, any DIYs??

found: http://www.audiworld.com/tech/int54.shtml

 

[diesel-a4]

anyone got anything else?

 

[diesel-a4]

well the matrix is working ok, tested all good. now i ran the on board test stuff threw the A/C displayed and got no errors reporting any flaps broken.

Anyone know where the hot pipe flap/servo is (ie it exact place). I have read that it may be behind the glovebox?

 

[diesel-a4]

ANYONE??? please

 

[aragorn]

the heater box is behind the glove box, ive no idea where the exact motors are that control the hot/cold air however the vagcat diagram may help you...

http://www.vagcat.com/epc/cat/au/A4/1997/156/56/1752063/

The temperature control flap is in the bottom left of the diagram, controlled by lever "2" and servo "12"

 

[jcb]

just for anyone reading this, fastest way to fix a blocked matrix is to swap the pipes round and then flush your coolant when said blockage is back in the system