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!