Had A/C re-gassed but still not working

adamtbray

adamtbray

adamtbray

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21 Dec 2015
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Hi guys,

Just a quick question as I took my car to have the A/C refrigerant replaced, as there was no cold air coming out. The issue is that the previous owner of the car had the system repaired and re-gassed only 15000 miles ago, so I was skeptical about whether it was simply needing new coolant.

I took the car to the garage, and asked if they could replace the coolant, and I mentioned regarding any possible leaks to the system being the cause of it not working properly. They said they would be able to test this before putting new coolant in. The question I have is, should they have put more coolant in, and tried to charge me, if there was no leaks in the system, or should they have just checked the compressor, as they basically went ahead with the re-gas, and then tried to charge me the money to do so after finding this wasn't the issue when the system was still not blowing cold air.

I just don't want to be fobbed-off if they should have known before putting coolant in if it didn't need it. I'm guessing you only need to re-gas the system if there are leaks in it? I said I'd head back to the garage tomorrow, but I haven't coughed up any money yet. If they've been reasonable, I'd probably just ask them to investigate other faults with it, otherwise I'll take my car somewhere else.

Any advice would be greatly appreciated.

Thanks,
Adam
 
The system is evacuated of old refrigerant and left under vacuum for a while to test for leaks before being refilled with the correct weight of refrigerant.
If you asked for the the refrigerant to be replaced and test for leaks that is what was done so you should pay them for it. You didn't ask for A/C system diagnosis from what you have said.
 
They replace the refrigerant if they find no leaks. Seems to be how the equipment they use works. It would have re-oiled and gassed the system anyway as part of fault finding. Unfortunately in this case, the refrigerant is not the issue.

What car is it? It could be as simple as a relay needing replacing.
 
Great, thanks for the response fellas. I've got the car going back tomorrow so I'll pay for the re-gas and go from there. I guess I should have asked them to check the compressor before a re-gas, but it could be another fault like a sensor I guess? Thanks, Adam
 
It's an Audi A3. I have a feeling it could be a faulty sensor. The windscreen wipers keep stop working intermittently as well now as well, so I'm concerned there is a fault with my car's electrical system. It's only a 2013 car but it's high mileage (120k)
 
I once wrote a guide on the Peugeot 306 GTI-6 forum on how to replace it.

As mentioned above, they can't just refill it without doing a vacuum test on it. If it overhauled 15k ago it's either got a leak or the compressor isn't working. It these issues should have been highlighted

Simple test: Engine running, press on and off the aircon. Do you hear a sort of tick/click from under the engine bay, and at the same time does the rev counter drop and rise ever so slightly? If it does, the compressor is working.

If the compressor is working, the system has enough refrigerant in it. Most compressors won't engage if there's not enough as a safety feature.

The weakest component is the condenser, the radiator looking thing normally clampled onto the actual radiator as it's open to debris, stones etc that can punch a hole in it. I once had a dead bird in mine!

Also if the car is old, the pipes can become pourus and only show weakness when it gets really hot.
 
Ok, thanks for that. Would they have known how much coolant was in the system before doing the re-gas? I've read the compressor won't work if there's no coolant to stop damage to the system. It's just annoying because he said he would check the system before putting new gas in and trying to charge me for it. Just doing the test you mentioned and checking the level of coolant would have narrowed the problem to the compressor, surely?
 
He probably meant check the system for leaks and not a full system check, so when it held vacuum he refilled the system. There are a few things it could be, seized compressor, bad compressor clutch, bad pressure switch, control panel issue etc.
 
Thanks, I got it re-gassed at a back street garage. In this instance I should have probably just taken it to kwik-fit for the re-gas. I'm taking it back for diagnostics later today so fingers crossed it will be an easy fix.
 
The problem is that when they suck the old refrigerant out and hold a vacuum to see if it holds the pressure that's the inverse of testing it when the system has refrigerant and running under pressure and in some cases the vacuum test will hold and show no leak. This is exactly what is happening with my car, vacuum test holds, add refrigerant and I get nice cool are for 2-3 days before all the refrigerant then escapes.

In cases like this they pump dye into the system and pressurise it to see if they can spot a leak, on mine the condenser was suspected which was changed but the same problem still persisted so in the end I just basically gave up as it looked simply like a process of elimination which was going to cost me, so these days as uncomfortable as it is I drive with the windows down :D
 
As its an A3 there is a fair chance it's a faulty pressure sensor. If you can get access to VAG-COM see if you have a fault code relating to the pressure. There pretty easy to change and about £40. Mine when bad on my mk5 Golf

There are some brands of the compressor which fail as well, due to the clutch, new ones don't have a clutch, mines a 2006 as doesn't. If it is a newer one the solenoid in the compressor can also fail.
 
Ahh I didn't realise the newer ones don't have a clutch. I reckon it'll be the sensor, and I've paid the guy £40 to diagnose the problem with the system. I keep saying I'm going to get a fault code scanner.. it would probably save me a heck of a lot of cash in future, as it feels as if Audi/VWs suffer from a plethora of electrical issues!
 
Another one with the high pressure sensor, had it go on my Mk5 GTI.

Any decent garage will not charge you if the A/C fails to recharge correctly.
 
So the current situation with this is that I purchased a compressor taken from a breakers yard, and I had a different mechanic fit this to the car. It turns out this hasn't fixed the problem, and so the original mechanic misdiagnosed the problem as being the compressor. What a waste of £40 that was! I knew I had good reason not to trust him, and was a good job I took my car elsewhere! After the new compressor failed to work, the mechanic hooked the car up and checked the fault codes with a VAG-COM reader, and unsurprisingly a faulty pressure switch came up. I've had this replaced and the system still doesn't work, however the mechanic informed me the temperature sensor was giving a totally inaccurate readout, which could be a source of the problem. I really don't want to part with any more cash to mechanics, so I'm going to get my own diagnostic scanner and try and source the problem myself. Has anyone else had similar issues with a VAG car?
 
I'd probably get the temperature sensor done. It's only going to be a few quid to replace. Did you buy a new pressure sensor, or a used part?

Also, do you have to regas the system after changing a pressure sensor?
 
I believe the system has a valve which stops the coolant escaping when replacing the pressure sensor. Yes, the temperature sensor may be a good idea to replace. I'm just wondering if it could be the condenser. How would you diagnose a fault with this? The original mechanic already confirmed there was power running through it, and the new mechanic didn't mention this could be the issue, but I'm just wondering now.
 
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