Aircon not working-help please

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MB Enthusiast
Feb 23, 2005
Surrey, UK
E350 CDi Sport&SLK250CDi AMG Sport
I tend to use my ac in the summer a lot and then in the cooler months when cooling isn't needed, I still let the compressor run a couple of times a week to keep things working ok. So today I ran the ac and thought I would set it to the coldest. I am not aware of any leaks or the like but it no longer gets cold at all. I have checked the relevant fuses and all seem ok. Normally when the ac is on, the noise from the engine bay is slightly higher, I presume from the 2nd fan kicking in and the clutch on the compressor being thrown. It no longer makes a louder noise, nor does the 2nd fan behind the grille kick in. This was a sudden failure, not a slow decline in ac efficiency. Any ideas what I can try next?
Hi there,

Most common fault would be a leak IMHO. When the refrigerant leaks, and eventually the pressure falls below a minimum level, the system will shut down and not run the compressor to protect the system. Hence it won't work at all.

If it's never been changed, I'd be checking the condensor (the air-con 'radiator' at the front) for leaks.

Make sure you take it to a reputable place for diagnostics, most garages have air-con equipment these days but unfortunately the majority of them just want to make a quick buck by 'gassing' the system before thoroughly checking it.

Thanks Will-Any idea what the condensor looks like and what would I expect to see if there is a leak? Oh, and I have owned the car for fours years and the system has never been touched and has always worked superbly-Up until now!
Condensor is on the front of the radiator and looks like... the radiator (same size so you don't really notice it.)

Leaks are most likely from rot behind the fan hubs, you can't normally see anything. Specialist will add UV dye to the system to help find the leak. Might be worth a check with a UV lamp as there may have been dye in the system anyway.
Thanks-I will have a closer look tomorrow. Being a skinflint, is it worth buying a can of 'top-up' refridgerant from Halfords and see what happens? Is it possible the level/presure of the gas has been lost over the years without an actual leak?

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