AC and Heater issues

[scristina]

Hi!

A few months ago (in end of the summer) the A/C on my 1997 A4 (1.9tdi) stopped working (didn't cool the air).
Since the Compressor was changed last year I took the car to the mechanic to see if it was some sort of leak in the system. Apparently everything was working ok and no leaks were found.
The A/C worked again fine for a 2-3 days and then stopped cooling the air again. Leak and component check was done again with no findings. By this time it was winter and I could not test it properly. So still don’t know if its working.
A couple of months ago the Heater stopped working. It blows air, but it isn’t heated.

Can these 2 problems be related? Can a Heater matrix issue cause both issues?

How can I solve it?

Best Regards

SC

[scristina]

To add to these issues! The Water Temp gauge is reacting slowly. It takes a long time to get to 80ºC than stays there for a while then goes up to almost 90ºC...

Is this all related???:confused:

NEED HELP PLEASE!

[scristina]

I've checked the AC system and at this point I know:

- AC system is charged to the correct pressure. So no gas leaks.
- Compressor is working
- The electric fan on the ac radiator is working
- The internal blower is working.

But still no cool air...

Can it be the electronic display / controller? How do I check this?

Best Regards

SC

[BrandonA4]

OK the temp gage is most likely the temp sensor usually located at the back of the engine easy fix i got one off ebay cheap works fine.
As for the no heat maybe your heater core is blocked there are two hoses that go onto the core on your fire wall beside the battery, when the car is cold remove both hoses and flush with your garden hose if water flowes through easy your heater core is OK, in that case it might be your thermostat. If thats OK your A/C heater control unit might be faulty.

[ike]

A faulty coolant sensor will prevent the heater from blowing warm air. The control system waits for a temperature threshold before switching the hot valve. Hence only cold air. It happens with a faulty thermostat too. Either are common problems.

[scristina]

Hi Guys

Regarding the temp sensor, amazingly it started working fine again. It must be the hot weather in Portugal :D:D

The Heather and AC still dont' work...

I will try to flush the heater core. Are the hoses easy to remove?

Regarding the AC there should be a diferent heat exchanger (from the Heater), right? So even if the heater core is blocked the AC should work. right?

Is there any way to test the AC control unit? Are they easy to get used? Where?

Thank You fro your help

SC


OK the temp gage is most likely the temp sensor usually located at the back of the engine easy fix i got one off ebay cheap works fine.
As for the no heat maybe your heater core is blocked there are two hoses that go onto the core on your fire wall beside the battery, when the car is cold remove both hoses and flush with your garden hose if water flowes through easy your heater core is OK, in that case it might be your thermostat. If thats OK your A/C heater control unit might be faulty.

[scristina]

Hi!

Where is located the "Hot Valve"? Since the sensor is working again (so the sensor and thermostat should be ok) and the heater isn't. Then can the problem be from the "hot Valve" Is there any way to check if its ok?

Thank You

SC


A faulty coolant sensor will prevent the heater from blowing warm air. The control system waits for a temperature threshold before switching the hot valve. Hence only cold air. It happens with a faulty thermostat too. Either are common problems.

[BrandonA4]

Not sure what you mean by a "hot valve" the heater core is part of the heating system it is on a loop. I'm pretty sure there is no valve it just heats up with the engine. So take both hoses off the core up on the fire wall by the battery they are held on by spring clips then run your garden hose into one pipe it should run through your heater core freely.

If your AC is not working you might have to get it checked for leaks or re gassed. Are the relays and fans coming on when you turn on the AC?.

[scristina]

Regarding the heat system. Ok!

Regarding the AC:

It's been already been checked for leaks and re-gassed with no findings.

What relays and fans?

Thank you

SC




Not sure what you mean by a "hot valve" the heater core is part of the heating system it is on a loop. I'm pretty sure there is no valve it just heats up with the engine. So take both hoses off the core up on the fire wall by the battery they are held on by spring clips then run your garden hose into one pipe it should run through your heater core freely.

If your AC is not working you might have to get it checked for leaks or re gassed. Are the relays and fans coming on when you turn on the AC?.

[BrandonA4]

The relay you should hear when you turn on the A/C a definite click and the auxiliary fan on the radiator may come on also.

[scristina]

Hi!

When I turn on the AC the the auxiliary fan on the radiator starts to work and what i think is the compressor clutch engages (Click sound).

Best Regards

SC


The relay you should hear when you turn on the A/C a definite click and the auxiliary fan on the radiator may come on also.

[scristina]

Hi!

Finally got the car to a "real AC professional". Apparentelly the compressor is not working properly. The High pressure is low (it was at 5 and it should be at 15 bar) and the low pressure was high (it was 5 and should be at 2-3bar).

Is this normal? The compressor was refurbished in 2009 so it was a real surprise...

Comments please...

[BrandonA4]

You may need to replace your AC compressor or source a good used one.

[jonathanfenton]

Like Brandon said. If the pressures are wrong and the AirCon Man said the compressor isnt working and i take it he took the pressure readings from the two filling caps then it would appear that your compressor is indeed not working correctly. Before you bite the bullet and buy a new compressor check both radiator fans are working. If they dont then the system cuts out whilst building pressure something to do with cooling the gas on the cold side of the Air Con. Once both fans have been prooved ok get a fault code scan done. Have a look but dont take them too seriously as they could of been in for years clear them out and then drive it for a few days using all the aircon settings then get another code scan so you can see which have appeared over the few days so you know they are current. Any switches/sensors that could be hindering you should be highlighted in the 2nd scan. If you cant be bothered with all that just replace the compressor and try your luck.

[scristina]

Hi!

Does anyone know the reference for the AC compressor for a 1997 audi A4 avant 1.9 tdi???