Thread: D4 a/c not cooling

Originally Posted by Graeme

The compressor is brand new and worked fine in cool weather 2 weeks ago. The pressures will be checked.

I agree with Brad and DJ regarding a leak. IME most new install faults are due to poor installation including lack of cleanliness during installation, which is why on the large systems I'm familiar with they are pressure tested with nitrogen before being filled, so I still favour a gas leak.

This brings me to my theory of why it it worked, failed then worked again. In my basic understanding of a/c it requires two shut off points to separate the low and high pressure sides, which I'd expect to be shut at rest, so it ran, then leaked half the gas (in broad terms) from the LP or HP side, resulting in an LP fault which was reset, ran again, shut down and leaked the other half of the gas, and won't cool now as the system is below the minimum pressure.

Originally Posted by RANDLOVER

In my basic understanding of a/c it requires two shut off points to separate the low and high pressure sides

There are no real shut off points. The compressor is a non-return valve and in theory the TXV might/can shut down while idle. In practice they both leak and a system will equalize in short order. Even refrigeration systems with pump-down solenoids have leak rate specifications for the solenoids. Everything leaks, even brazed copper pipe.

In my case, I pumped out and re-gassed the car (it was 150g low) only for the missus to complain after a couple of weeks "The aircon is ****". Turned out to be the low side service valve that with hindsight I should have replaced while I had it open. I now just replace them as a matter of course any time I'm in there.

That reminds me, it has been about 5 years, I should probably do it again.

You raise an interesting point a few years ago I had my a/c pumped down measured and topped up as it was short of gas, after it stopped cooling a couple of times I'm not sure they replaced the schrader valves though, I'll have to ask my mechanic.

Regarding copper pipe leaking, the cheaper it is the better it leaks!

As it happens I’m replacing the compressor, condenser and dryer on mine soon DIY. Will get it degassed, so the work, get it regassed. It has done nearly 400,000km. Figure it’s due. I will use genuine new seals and will do the schrader valves as you suggest
Getting the parts trade through Josh, a former member here, and borrowing his AC knowledge.

Originally Posted by Graeme

My old D4 had a new genuine Denso a/c compressor fitted with the engine swap. The vehicle isn't being driven. Some time after the a/c was gassed with Hychil, the a/c was found to not be cooling at all but then worked very well as soon as a climate control fault was cleared, with the fault possibly caused by an earlier totally flat battery. Now a couple of weeks later, the a/c again doesn't cool.
Static pressure of around 89 psi rises to around 103 psi with the engine running. The pipes are basically ambient temperature and the evaporator temperature several degrees higher. The clutch is engaging when the a/c is switched-on. No faults are recorded. Being a new compressor, the assumption is that the flow control valve in the compressor should be OK. The connector for that valve is inaccessible so the effect of unplugging that connector can't be determined. Unplugging the pressure sensor connector causes several faults and when refitted and the faults cleared, the faults don't return. The battery was disconnected for 30 seconds to force a restart of the climate control ecu, but without any change.

Does anyone have suggestions of possible causes or tests to try please?

Passenger side wheel area.

Drop the plastic off the bottom front, reach in from there...

We concluded that the connector on the compressor valve would be assessible but not the one at the wiring harness join which is on the engine side of the turbo intake tube. We had removed those little heat shields hoping to find that join.
I have a vague recollection that the compressor arrived fitted with new seals and there's an old a/c pipe join seal resting in the top of the exhaust manifold, suggesting that those seals were replaced in the regassing job.

Mine had leaks in all 3 pipe joins, 1 in the rear of the PS front wheel, 1 just behind the air tank and lastly up above the rear axle.
Replaced all the O rings, problem sorted.

G'day Rich,
Fortunately no rear a/c in this case.