Hi everyone - wanted to update you on the process of refilling the R134 coolant in the R class. This is pretty easy but like all things R it takes more time than it should.

First the background. After a cold northeast ohio winter we had a string of 75 degree days in early may. Our 320 has been quite reliable and not needed much more than the factory service intervals. Well...when the temp hit 75 the AC went on and I got a blast of hot air. Terrified, I turned to the forums to read about AC clutch replacements, compressor failures and other doomsday conditions. What was puzzling me was that this problem happened virtually overnight. The only preceding clue was a series of unusually cold AC blasts at startup. This happened 3/4 times before I would raise the temperature to make it comfortable. The next morning - surprise! Nothing but hot air from the vents. Hotter than ambient at first and felt like it was cooling the turbo itself. I decided it would be easy and inexpensive to try a recharge. After all, if the compressor was toast, it was a dealer trip regardless. And we all know that is a $1000 adventure no matter what’s engine done.

I went to advance auto parts and bought a 20oz can with a gauge for $37. The manufacturer AC Pro (because now I am one) has a nice website where it identifies the low pressure port of the ac system. Easy enough I connected to the port. Uh not so fast Herr Shadetree mechanic said the Benz designers. Turns out the strut tower crossbar/brace panel totally instructs the refriderant canisters connector...here we go. I removed the engine cover and the four bolts on top of the strut tower panel. Then used my 1/2” drive socket as a wedge to hold the panel up about 2” so I could acces the port. Finally I could connect!

The process of adding R134 is fairly simple - which makes it perfect for me. I followed the instructions and emptied the can of about 10 minutes while he little gauge rose slowly to 10psi. The gauge indicated 30-40 was full. Now what? Lacking all
other options I called AC Pro and discovered the R class hold about 34oz of coolant. Swell...back to advance auto for another can of coolant. Well guess what, the options are either a 12oz can for $27 which will not reach to 34oz minimum or another 20oz “kit” for $37. Sending a global conspiracy, I bought the larger and went back to work. This time it took about 20 minutes to discharge the entire can and reach 35psi.

And just like that...$78 and two hours of work / driving to the store later and the air is cold again! Like most things R class, I could repeat this in 1/3 of the time next time. Given how will this 2007 has been running I doubt it will be with us in about 11 years but who knows:-! Good luck to all who try this!