Hi all,

Octy 1.9tdi Ambient

I have spent the last hour browsing through the various posts on Air Con problems but haven't been able to get any further leads.

If I describe what I have done so far perhaps a kind soul can offer me some advice.

1) The A/C was recharged about 2 years ago and I noticed that there was little or no improvement. I have generally not been using it.

2) Went to use it about a week ago and no cooling what so ever.

3) took it into a Air Con specialist 2 days ago who identified a leak near the condenser lower pipe fitting.

4) He cleaned the joint and ally welded the condenser

5) He checked the refrigerant and noted that there was only about 100ml and filled it back up to 700ml

6) I have checked the compressor by removing the under tray and wheel arch liner and noted that the clutch bolt and nut are still sound and the clutch engages the compressor shaft when switching on the A/C

7) Voltage test at the Comp. reads 12.8v

8) Both fans operate when switching on the A/C

9) I get cooler air for about a minute before it then returns to outside temp. the compressor clutch is still engaged turning the compressor.

10) New Pollen filter fitted - no difference

11) Normal temperature gauge reading

12) No obvious signs of any other leaks at any of the fittings

I saw the pressure gauge that he had fitted to the top connector by the slam panel and noted that the pressure dropped very slightly when first switching the A/C on and cool air was coming out and then the pressure rose very slightly as the cooling stopped.

It would appear that what little cooling I get is only at engine idle speed

Just checked VAG and the following fault recorded

"1 Fault found:

17664 - Engine Coolant Temp Sensor (G62): Open or Short to Plus

P1256 - 35-10---Intermittent

Readiness: N/A"

I have been aware of this fault code in the past when I noticed that the temp gauge sat at zero. I unplugged the electrical connector and plugged it back in and the gauge has worked perfectly ever since. The fault code is displayed even though the temp gauge reads correctly.

I have owned the car from new. It has covered 90,000 miles and is in excellent condition and fully serviced.

I have run out of ideas (and money)

My hunch is that the compressor and clutch are fine and that this fault lies elsewhere.

Any help greatly appreciated

Thanks :S

What you really need to know are both the high and low side pressures.

From just the low side pressure rising after initially falling, it is likely to be the compressor if the shaft of the compressor (nut in centre of clutch) is still turning.

If something in the system was blocked (drier/TXV), you would expect the low side to fall as less refrigerant would be getting back to the suction port of the compressor.

Do you remember what the high side gauge was doing?

What you really need to know are both the high and low side pressures.

From just the low side pressure rising after initially falling, it is likely to be the compressor if the shaft of the compressor (nut in centre of clutch) is still turning.

If something in the system was blocked (drier/TXV), you would expect the low side to fall as less refrigerant would be getting back to the suction port of the compressor.

Do you remember what the high side gauge was doing?

I didn't see a second gauge attached. I will go back and ask.

As a matter of interest, how else can a compressor fail apart from the clutch mechanism?

Many thanks

The most common failure where the shaft is still turning, is failure of the wobble plate drive gears or more specifically the ball that sits between the gears. The ball can disintegrate and is usually caused by overheating.

If the guy you took it to was relying on a single gauge, he's not much of an a/c specialist - suggest you go somewhere else.

If the guy you took it to was relying on a single gauge, he's not much of an a/c specialist - suggest you go somewhere else.

Absol-fvcking-lutely!!

Absol-fvcking-lutely!!

I refrained from asking if the gauge was attached to a can

Thanks for the replies. I went back today and confirmed that he vacuumed the system for 30 minutes. And added 700 grams of refrigerant. He connected the pressure gauges to both the low and high circuits.

Engine off

low pressure was 6.9 bar

High pressure was 7.5 bar

Engine running A/C on

Low pressure dropped to 3.4 bar

High pressure climbed to 8.5 bar

The only unknown as I can see it is that the drier is clogged. Failing that it can only be the comp.

Any further thoughts?

Thanks

A rule of thumb calc gives about 32°C ambient at 7.2bar with the a/c off. I can believe this figure so I assume the circuit has the correct fill.

I would expect a good compressor to give roughly 14bar on the high side and less than 2bar on the low side under normal conditions. Stressing the a/c by putting the a/c on, the blower on full and temp on max heat should give even higher high side pressures.

What you're seeing would normally indicate a faulty compressor. If the drier was clogged, I would still expect the low side to get down to under 2bar and probably lower. Even if the TXV was bad I would expect the high side get above 10bar.

I have to ask. You went to an a/c specialist - what did he diagnose? After all he had the car in his hands.

Thanks for your reply, he says the compressor is faulty but recommended it would be worth changing the drier before shelving out for a compressor. The drier is the original one and 10 years old.

Cheers

eurocarparts do an octavia one quite cheap - google for it, it is around £20