MrAnthonyWong

I have a 2004 ML350. There's a leak in the AC system somewhere, usually a full-reload lasts me 3-6 months. It went out earlier in the spring/winter, but in SoCal, temperatures were mild and I got lazy. So it's probably been blowing warm/room air for the last 3-4 months.

Of course we hit a heat wave, and I tried to refill it using the usual hose/gauge I use with some cans of R134A. The usual, I have it blowing on COLD on MAX, and hook it up to the LOW Pressure side. Usually here it starts taking the R134A and both the can gets cold, and LOW Pressure side line around the nozzle/connection gets frosty/cold, so I usually know it's going. I also tried a new hose/gauge. Same result.

But right now that's not happening. As far as I can tell visually the compressor is going when I look by the fan? It's all spinning. Did I leave it sitting on such low refrigerant levels that it tripped a code and it needs to be cleared for the compressor to engage/accept the R134a?

A few times the can and low side line got frosty/cold, but then it only took for maybe 10-15 seconds, and both can and low side pressure went warm. And even 15-20 minutes the R134a can was still full. In the past, this usually was never a problem and it would instantly take.

Any ideas of my next steps?

Thanks!

Dfixit1

There seems to be a few possible issues. You could have a bad pressure switch not respondingto a signal from the AAM and allowing the Compressor clutch to kick in and run. You may have AAM codes or a bad AAM, freon leaks causing or contributating to this as well. Don't worry about the electric condenser fans just yet. With what ever freon you might have in the system, turn on the A/C switch inside then look VERY closely at the front of the compressor to make sure the very front of the compressor clutch is pulling in and spinning. MOMMA-Benz is very watchfull over her A/C systems. You could have a leak,, or the pressure switch may be bad, or too low or too high on freon. From dead empty of 134a and drawn down into a vacume that holds 30 in Hg./ 30 inches of mercury into vacume, it should be about 27.1 ounces. There is some information usually on the top of the fuse cover box that says how mutch 134a is required,,, too much,,,,,NO Good,,,, Too Little,,, No good either. .
Keep us up to speed with what you find out.