Finding leak on AC system

[rabbituk]

After getting messed about twice by a local aircon technican w.r.t getting a diagnosis done, I've decided to have a go myself. I know some on here have replaced AC hoses in their cars so was curious to know how they checked for leaks. I have access to a vacuum pump and air compressor. There is definitely a leak somewhere as it was charged just over a year ago and is now empty. In terms of finding the leak, various forums seem to suggest using nitrogen but this seems a lot of faff - I'd need to by a nitrogen tank and regulator it seems to hook up to the AC manifold gauge. This looks to be costing over £100 for something that I will rarely use. Is using compressed air okay for finding the leak so long as I'm not running the system?

[Luxobarge]

I've spent ages and a lot of money in parts and re-gas to get my aircon working properly and reliably, so I feel your pain.

Don't try diagnosing it with compressed air, for one you'll probably introduce moisture into the system and secondly it's very unlikely you'll find the leak because the leak is likely to be so tiny that it will be undetectable. If the leak was bad enough to show up with compressed air, then it would have failed the vacuum hold test during the re-gas process. This is a mandatory legal requirement during a re-gas, where the system has to undergo a deep vacuum and hold it for a prescribed period of time, to check for leaks. If it doesn't hold the vacuum, then it may not be refilled with aircon gas. Even this isn't a perfect test, as every time mine passed the vacuum test, but there was still a leak that allowed the gas to escape over a period of time.

The only way we found the tiny leaks was to re-gas it with an ultra-violet additive in the gas. Then a UV detector is used around the system which will show up even the slightest trace of escaping gas. This is a standard procedure for any decent aircon tech., and it worked well.

Unfortunately, if this is done the system then has to be emptied again by the aircon machine before the leaking part can be replaced, then re-gassed, so it can get a bit expensive, but worth it in the end.

Although there are some common leakage points (condenser, receiver-dryer etc.) I wouldn't be tempted to throw parts at it in an attempt to cure the leak as one leak I had was on the filler nozzle union fitting - not a common leak point!

During my saga the compressor itself failed (very noisy pulley bearing) so I ended up replacing a leaking condenser, a leaking receiver-dryer and the compressor itself. The system is now pretty good although I still need a re-gas every 2 or 3 years.

If your local aircon tech can't or won't do the above, then I'd change to another technician if I were you, as UV additive is a pretty standard diagnosis technique and should be straightforward.

I now always ask them to include the UV additive in case I get any more leaks.

Hope that helps

[ITSv40]

Exactly as Luxobarge says.

It is illegal to work on aircon unless certificated. Fine to replace components on an empty system, but then needs testing and re-gassing by a qualified techie.

[rabbituk]

I believe the intent of the legislation is primarily concerned with discharge of high COe gases into the atmosphere. However as the system is empty I do not believe this is a concern in this instance.

It is such a pain when let down by garages. I can change the oil & filter on my car in the time it takes to drop car off and pick up courtesy car. But for this I need equipment that I do not have. I will try making contact with an alternative garage who might have nitrogen who I do trust although they don't have the ability to charge the aircon. I replaced the receiver dryer last time when it hadn't been working for 10 years - shown up by a UV dye. Might be possible that I pinched the o-ring or something silly like that. And hopefully there will only be a single leak point!

[4x4]

Avoid A/C shops that use 'all in one machines'. Find an 'old school' A/C expert who used gauges a gas bottle and scales.

Modern A/C machines do not diagnose faults, the vacuum test is an inefficient way of checking for leaks in the system and most cars will pass the test unless there is a massive leak.

Nitrogen is the best method of finding leaks, it is filled under pressure making it easier to detect where the leak is.

Dye is automatically put into the system when filled by modern A/C machines, oil is also automatically filled (albeit the operator has to let the machine know the quantity)

[rabbituk]

Well it is on to the next garage having paid for an hour of diagnostic time and no leak found - there definitely is one. Also frustrating to be without the car for 2 days. The garage I tried and I have used for many years on various cars failed to find the leak. Not sure how to identify a local old school AC technician. Still very tempted to do this myself by getting a nitrogen tank.

[ITSv40]

Are you using a general garage that also does aircon or a specialist? I use a company in Kettering who are aircon specialists - they work with manufacturers designing systems. Have used them for over 20 years and never had an issue with them and they are competitive on price with the 'fill and scarper' outfits. I'm sure there must be similar in your area.

[rabbituk]

The first place I tried was a local garage that also did aircon. They had a prominent sign outside offering aircon services. Having 2 appointments at that garage - the first appointment was the garage didn't have the tools necessary because they'd lent them to a friend, and then the a no show at appointment time. Obviously not seriously in business.

The second garage is one that I've used for years but they only have a nitrogen tank and don't do refills.

[Kev0607]

Originally Posted by rabbituk

The first place I tried was a local garage that also did aircon. They had a prominent sign outside offering aircon services. Having 2 appointments at that garage - the first appointment was the garage didn't have the tools necessary because they'd lent them to a friend, and then the a no show at appointment time. Obviously not seriously in business.

The second garage is one that I've used for years but they only have a nitrogen tank and don't do refills.

Google may be your friend here (A/C specialists in your area)...

The first one sounds shady anyway... I'd avoid that place. If they can't be bothered to turn up, then that's enough really... not a proper business.

The second isn't an A/C place either. If they can't regas, there's little point going there for that particular work.

You can't do A/C work yourself if you aren't registered to do it (not on a system that still has refrigerant in it anyway... I think empty you're okay. However, you don't have the right equipment to regas it (or the certification)... You're back at square one.

I understand you want to find the leak, but as you say yourself, there's little point buying equipment that you're rarely going to use. You may as well let a professional do it... just have to find one. There's plenty of them out there.

Not to sound harsh (that's not my intention, just being realistic), but if you're without the car for a day or so, it is what it is... If you want it doing right, it needs to go to a proper place. Yes, the inconvenience sucks... but there's nothing you can do about it, as you can't regas it yourself anyway.

I think your best bet to find someone that uses the old school method (bottles of refrigerant and scales), possibly a mobile a/c specialist? Its unlikely that a mobile specialist will carry a big expensive "all in one machine" around in a van incase it gets robbed (although, they might use modern equipment for ease nowadays). Then, at least you'll still have your car and its not going to be parked in a garage for days on end... Any reputable mobile a/c specialist will check for leaks anyway prior to a regas if they're using the old school method. They should do the same if they have a fancy machine, but they aren't always accurate (hence the suggestion of scales/bottles of refrigerant). It has to be a massive leak to fail a leak test on a modern a/c machine... these "all in one" machines rarely detect small leaks. Or, if the mobile person doesn't have the old school equipment, explain to them that you're regassing it and it only lasts a year. See if they can help find the issue with UV dye or nitrogen.

If you can't find someone mobile, then it has to be left in for a day or so at a garage. Sadly, there's not much you can do. If it needs fixing, it needs fixing. They have other cars to fix too, so that often means it won't be an "on the day" fix for you. Just explain to them that the refrigerant doesn't seem to last... they should test the system properly then, as opposed to doing a fill and hope it doesn't leak sort of job.