Air con question

[Martin blackett]

Hi all
Can anyone answer this
W169 2007. When go for regas it won’t hold vacuum. Large leak. Tried to override but machine said no. Leak to large. Put in nitrogen and attached a gauge to the port. No pressure loss show on gauge after 24 hours.
next job is to uv dye it and put nitrogen back in to hopefully find.
Sprayed all pipes and joints we could find with a gas detector and fitted new condenser and dryer new o rings etc.
Seems odd to me the untrained why the nitrogen is still showing on the attached gauge.
thanks

 

[SL63 Mark]

I'm no expert, but maybe the Nitrogen has a larger molecule than the A/C gas. Maybe it doesn't want to escape.

UV dye is the way to go. I have never heard of Nitrogen test. Seems to waste 24 hours for no reason.

 

[Richard Moakes]

Usually a compressor shaft lip seal, which holds under pressure but leaks under vacuum

 

[Martin blackett]

Usually a compressor shaft lip seal, which holds under pressure but leaks under vacuum

Thanks. Is that a major job ? Or just change the compressor. I presume it would show uv due would it ? Where in the comp is it located ?
thanks

 

[Botus]

nitrogen is much bigger than air... but u don't get air in a AC system. No idea what size that stuff is.

I would expect the condenser is worn out....

 

[M80]

If the condenser has a hole it should be apparent with the nitrogen test.
While mt it might be worth replacing the pressure sensor.

 

[Richard Moakes]

Thanks. Is that a major job ? Or just change the compressor. I presume it would show uv due would it ? Where in the comp is it located ?
thanks

Sadly won’t show UV dye, and will leak refrigerant very slowly but will not hold a vacuum to pass a test on a wheelie bin AC machine.

Best option is a new compressor but also worth getting an AC engineer to run an ultrasonic vacuum leak detector over the whole system before spending money.

Vacuum is a strange test, lowering the system to 300 microns is nothing like the pressures when the system is running and puts very different stresses on the seals.

You need a proper AC man, not a button presser with a machine he got 10mins training on.

 

[Martin blackett]

does anyone have a table of how much gas and pag oil the system holds
A150 2007. Manual air con. Thanks

 

[Richard Moakes]

770g R134a 120ml PAG46