Air Con isn't working....again

sand_hun

Hi folks, I have a VW Polo. In Summer 2022 the AC stopped working. I took the car to a mains dealership and paid for an AC diagnostic and AC service. I believe they used some kind of dye to check if there were any leaks but none were found. The air con worked for a few days but then the hot weather went and there was no reason to use it.

By summer 2023 I had the same problem. This time took it to Halfords and paid for another AC diagnostic. They charged me for an 'AC service R134a' and for a new dust/pollen filter. The air con worked for a few days but then stopped functioning again.

Any ideas what this could be or the best course of action to take now on? Bit fed up of paying for diagnostics and re-gassing without getting to the root cause. Thanks.

Mildly_Miffed

Apart from stone damage to the condenser (in front of the radiator, so quite vulnerable), "not using" aircon is the best way to make it not work. The fact it worked for a few days suggests a very slow leak, so - no - any UV dye that'd been put in it may well not be visible.

The seals in the compressor are lubricated by oil suspended in the refrigerant gas. Without use, the oil falls out of suspension, the seals dry out, shrink, and the refrigerant gas escapes.

Aircon is at its most useful in the UK in weather like... this. It is quite simply THE BEST WAY to clear misted windows. It dries air, not just cools it. The heater system then heats the cooled dried air, leaving you with warm dry air - ideal for clearing windows and keeping them clear. Just leave it on all year for reliability. It adds VERY little to fuel use.

droopsnoot

I don't know how similar your VW is to my Audi, but on my car, if the cooling fans aren't turning, the air-con won't be very efficient at cooling the air. It'll warm up, but when you try to put it on a lower temperature, it won't cool properly. On my car, there is a poor connection on the fuse that supplies current to the cooling fans, and that it turn causes the fuse to get warm, start to melt the holder, which in turn makes the connection even worse, and so on until the fans don't get any power and the air-con stops working properly. It's a known fault on the model, not just on my actual car.

So, on the off-chance that the set-up is the same, it might be worth checking if the fans are working - on my car, if the air-con is on, the fans should be turning, regardless of whether the engine is warm enough to need cooling down. I'd have expected the main dealer to notice something like that, not necessarily Halfords. I think a lot of places presume that if the air-con isn't getting cold, it's because it needs new gas. I paid for new gas in mine, noticed that it still wasn't cooling, mentioned it to the person who'd done it and their next suggestion was that the compressor needed replacing. I looked up the fan thing online, I just wish I'd looked it up before paying for new gas that wasn't needed.

SonOfPearl

I'm not a car expert, but I had almost exactly the same problem with my VW Polo. It turned out there was a small leak in the condenser. 

daveyjp

The root cause will be a leak too small for dye to be noticed.  It could be a minor leak around a seal, a slightly split pipe, a small condenser hole.  I had exactly the same issue on both an A class and B class Mercedes at about the same time when both were about 4/5 years old, both small leaks.

On a Subaru it was a poor weld on a condenser, changed under warranty,

If it does get fixed leave aircon on all the time to keep the system healthy.

born_again

sand_hun said:

Hi folks, I have a VW Polo. In Summer 2022 the AC stopped working. I took the car to a mains dealership and paid for an AC diagnostic and AC service. I believe they used some kind of dye to check if there were any leaks but none were found. The air con worked for a few days but then the hot weather went and there was no reason to use it.

By summer 2023 I had the same problem. This time took it to Halfords and paid for another AC diagnostic. They charged me for an 'AC service R134a' and for a new dust/pollen filter. The air con worked for a few days but then stopped functioning again.

Any ideas what this could be or the best course of action to take now on? Bit fed up of paying for diagnostics and re-gassing without getting to the root cause. Thanks.

Leave A/C on.

Not using can cause seals to dry out & you get problems like yours.

Stateofart

First thing - echoing the comment above.  Use it or lose it when it comes to A/C.  At least once per week run your A/C, even in the winter.

Next thing, yes holes in condensers/evap cores do happen and will result in loss of gas, especially if it's within a few days.  How old is your car?

oldagetraveller1

Could there be a small leak in an inconspicuous/inaccessible place, e.g. the evaporator? Quite possibly any signs of dye cannot be seen. More likely to be detected with a gas "sniffer" in those circumstances.

sand_hun

Stateofart said:

First thing - echoing the comment above.  Use it or lose it when it comes to A/C.  At least once per week run your A/C, even in the winter.

Next thing, yes holes in condensers/evap cores do happen and will result in loss of gas, especially if it's within a few days.  How old is your car?

Thanks for the info/replies. It's a 2015 model. It doesn't actually get much use, only 4,000 miles a year as I go most places via bicycle and/or train.

sparklymarkly

Leave the AC on all the time. Using it keeps the system running properly.
It doesn’t have to be blowing cold air - just having it on and pumping warm air still keeps the system flowing.
Whereabouts are you based? There’s a brilliant AC specialist in Derby - way more knowledgeable than a dealer or Halfrauds.

lordmountararat

I never switch the A/C off. Climate control sorts out the temperature in the car.