Aircon test

[Keggers]

Looked at a 964 with aircon today and the aircon wasn't functioning. Seller has indicated he is more than happy to get it regassed, but not sure that will be enough to let me relax, as from what I understand it would be more than likely it would work fine for a few weeks or month and then leak out and need regassing again.

Is there any way I can get my mechanic or an aircon specialist to confirm that it will actually hold the gas over the long term. I know they will all need periodic regassing but I'm meaning can anything be done to test the system is ok rather than waiting and discovering in a few months that it has lost its gas again?

Not sure how relevant this is, but I sat it in neutral and tried turning the aircon switch on and off but didn't see any change in the engine revs. Had thought it should drop revs slightly when the aircon was turned on?

Cheers
Greg

 

[Dave Wilkinson]

Greg,

Firstly, if the system is out of gas (or even just low) the engagement clutch on the compressor will not operate - so no additional load on the engine to affect the tickover.

Any competent a/c engineer can do a pressure test. They pressurise the system with nitrogen and sit back and wait. If the system holds pressure for an hour or so it's promising although not absolute. They can also regass with a UV dye which can make any leaks visible with a UV light although that's a longer term check - you won't see any obvious results from that in a few hours.

As with any a/c system, there are a lot of parts which can suffer from old age and the 964 is no different. The system was designed to use the R12 gas but that is illegal to use now so they must be refilled with R134a instead. It's not quite as efficient as R12 but is better than nothing. Ideally the valves need to be changed (although not absolutely necessary) and so people will argue that the receiver/dryer needs to be changed too - but I didn't chnage mine.

The expensive bit comes if the problems turn out to be with the conpressor or - heaven forbid - the evaporator. The compressor can be refurbished (or on exchange) but the evaporator must be replaced if faulty. You're looking at around £500 for the evaporator/valve parts but probably that again for the labour if you're paying someone to fit it.

A simple regas should be yours for around £60 - £80 depending where you go.

Hope that helps.

Regards

Dave