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Some sympathy from me too as my car has had AC issues being investigated by 2 different certified repair places since April and after significant time and money invested it is still not working. Both places actually did not take full price for time spent on investigation which was nice gesture.
They are now quite sure that fairly expensive Front Elektronic Module needs replacement but they are on back order from factory, arrival time in September maybe. Luckily we have other car to use during the hottest days.
Took it into Mercedes, and they said there's no leak. They have a fancy machine that draws a vacuum in the system, and if it detects any leak it won't fill it, but it found nothing. The previous people reckoned it was losing pressure in a few hours so that would have to be a decent sized leak. I'll see if it's still working tomorrow.
Weird though, not sure how come the specialists found a leak. They showed me the pressure gauge having dropped, they showed me the detector picking up gas in the cabin. And they said they wouldn't do the evaporator replacement anyway, so it's not like they were trying to rip me off. Odd.
It worked really well this afternoon at any rate, which was lovely. However this does mean we drove around all holiday without aircon when we didn't have to! My wife even got a bit poorly on the way home because of the heat.
I was thinking about this thread on the way into work this morning. Been a while since I used the can of stop leak stuff and gave it a top up but it’s still blowing out air as cold as the day I did it. Without wanting to jinx something, I think it might have actually worked.
They have a fancy machine that draws a vacuum in the system, and if it detects any leak it won’t fill it, but it found nothing.
I have a similar machine. Vehicle can pass the vacuum stage, but will still leak because the vacuum has pulled a seal (for example) back into place and effectively sealed the system. The only proper check is with OFN or a 'sniffer'.
Small leaks can be bloody hard to find. Most are (in my experience) caused by damage to the condenser from stone chips/corrosion.
If you suspect the evaporator, then seal up the condensate drain and run the vehicle for couple of days. Release the seal and if there is any dye (assuming there is some in the system) visible you've more than likely a leaking condenser. Extremely rare and never worth fixing - unless you DIY. Sell the car if you really want AC.
They said they'd sniffed it and not found anything. I can't figure out what sequence of events would lead to the specialists finding a problem and Mercedes not. But we'll see what happens down the line. The original leak took about 36 hours to empty, but that was the condenser, it was obviously bad and that's been replaced.
There is dye in it. The drain tubes come out on top of the transmission so I can't imagine they are easy to get to, but I might be able to get a UV torch on it and see something.
EDIT hmm detectors are only £20 on Amazon.
@tjmoore
[I]Following this. My Civic air con needs sorting out and garage say it’s a leak and needs new condenser,[/I]
We had an 09 civic, symptoms were that the air con would work briefly and then turn off after a few minutes of driving, so I was pretty sure it was still pressurised. Dealer solution was to replace the compressor (and empty/ refill the system...£££)
I got a recharge from Kwikfit followed by their money back guarantee when it didn't fix it (no leaks found)
After a bit of Googling, I spent a few quid on some shims and took the clutch off the compressor (don't need to empty the refrigerant). It already had the thinnest shim in there so refitted it with no shims.
Result, perfect ice cold air con 🙂
If it's a leaking condenser, it should be very visible. The refrigerant evaporates but it contains oil which gets left behind. When I took the cover off mine underneath it was a hell of a mess - very obviously had been leaking for ages.
The fault-finding process will be driven by the warranty company rather than the local MB dealer and their workshop. It might take several small steps spread over days
Is this your troublesome Mercedes @molgrips?
~20 years ago I had a LWB A-class. Great little car. Aircon became feebler and feebler. MB happily explored it a few times for £££. Typically no fault found and they would re-gas. Only for it to fade away within the week. Problem eventually turned out to be a bent and cracked joint on the ‘radiator’ caused by inept fitting in an earlier inspection.
Good luck.