Brian McL

Here's one....The A/C on a '92 300E doesn't blow cold, but hold on ! The system is tight, no leaks and the gas is full plus the compressor works fine as does the fan. Now, after the system is on for a few minutes the line from the dryer to the expansion valve becomes covered in ice....white as can be...and if I leave the system on long enough the whole line AND expansion valve become "frosty"....but no cold air in the car. How could the gas be expanding in that line past the dryer? Is the expansion valve blocked? I hope somebody out there has seen this before and can explain what is happening 'cause it has me totally confused. Thanks

ashman

perhaps the ac needs a recharge? are you sure it has the right amount of freon in it?

AshMan

Brian McL

yup....the system was completely evacuated, pressure tested and then re-filled.

mhorn

on that note, what's the process for charging the a/c system? I looked in the factory repair manual, and they tell you how to do everything except charge up the system. I take it you want ot charge on the low side (suction). My '91 300E is not blowing very cold air. With the A/C on, I can see cloudy bubbles in the freon window. I have some R12, but I didn't have the right type of line to go from the tank to the car. Anybody have any experience with this?

Brian McL, sounds like either you have a bad expansion valve or a clogged evaporater coil.

Brian McL

I f you have R12 then fill on the low prressure side...on that car there is only one spot to put it in.....right by the strut tower. You will need to get the correct adaptor. I think it is the expansion valve, but not sure.

gpracer

The high side line should be hot liquid until the expansion valve. If it is cold at any point before the valve, there is a restriction at that point, and that part should be replaced or cleaned out if possible. Feel the line temp all the way back till you can feel where hot meets cold, thats the restriction.

Brian McL

OK...so if I read you correctly then, the restriction would be in the dryer, because the line from the dryer (including the site glass) to the expansion value is ice cold. Could the dryer be the restriction?

gpracer

If the line from the condenser is hot all the way to the dryer inlet, and the dryer is cold and the system is charged correctly, the dryer is most likely defective or plugged/restricted. Sounds like an easy fix.