I had a problem with my 400E recently. I thought the system was low, because it wasn't as cool as I liked. So, without gauges, I threw in a "few" cans of R-134A. Then, thanks to Arthur Dalton, I learned that my low speed fans were not working. Once I got the fans working, the air still didn't work well. Finally, I bought some cheap gauges from Harbor Freight ($46.00) and checked the pressures. I found out that my high pressure side was going up so high that the compressor was actually cutting out. Once I extracted some R-134A and got the pressures back down to where the manual said they should be, it worked fine. Do you have the gauges? I know the Harbor Freight tools are generally cheap, but they worked for me and I don't use them everyday anyway. The best thing I did was buy the gauges. I did all three of my vehicles. You'll get a better picture of what's happening and those on this forum with more knowledge than you or me will be better able to help you.

When they recharged it two months ago, they might have actually overcharged it and the higher seasonal temps are now causing the compressor to cut out. Best of luck.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles