skukreja;
My 1995 Quest had the exact same problem.
The bottom line was a blocked orifice in the liquid line.
It's a long story, but after my battle, I feel I have to tell it.
The car had worked flawlessly up until this year, when the air conditioner just quit cooling. I bought a Haynes repair manual, searched the web and talked to at least 10 mechanics. All said the same thing: Take it to a repair shop.
I did. After a $2,175.00 estimate to replace, the rear evaporator, all manifold lines, accumulator, compressor and radiator fan, I decided to tackle it myself no matter what the outcome.
Initially, when the unit stopped cooling, I started by trying to add R134.
No matter what guages I used, they showed pressures way to high! (thats when I bought the manual and started talking to mechanics) All sources pointed to a blockage in the system. When the repair shop told me it was empty and they charged me $384 to evacuate, refill and estimate. I proceeded to tear the entire system apart.
This is not easy. I don't reccommend it. I already have. The end result was a clogged orifice tube, located in the liquid line that runs from the condenser to a "T" fitting and then straight into the evaporator in the firewall. the other side of the "T" goes to the rear evaporator, where the orifice tube is contained in the the elbow connecting the manifold lines to the rear evaporator, under the car.
I replaced this line,(it comes with a new orifice) about $60, and a new accumulator, had the system evacuated and proceeded to reinstall 52(not 48) ounces of R134, and oil. Keep in mind that after evacuation, you will have to jumper the low pressure switch on the accumulator to get the compressor to run, until there is a sufficient amount of R134 in the system to keep it closed. By the way, the compressor made unusually loud noise until there was about 30 ounces of R134 in the system.
After about 40 ounces of R134, the rear unit started cooling first. It will do this as it has a Chrysler "H" style expansion block at the evaporator. At about 48 ounces the front system started cooling. With a full 52 ounces, the entire systems started working again.
In 100 degree weather(north Texas) at idle the front unit will produce 48 degree air at the vents. In city driving, about 42 degree air, and on the highway, after a couple of minutes of driving, right down to 33 degrees. the rear unit produces slightly higher temps but not by much.
Keep in mind, that it requires a special tool to take all the manifold lines apart and access to them in the engine compartement is down right insane, not to mention nuckle busting. Access to the rear requires you to safely jack up the car, and dissassemble the entire driver side interior. and working with high pressure lines is inherently dangerous, so use all precautions.
the real question to ask: Is it worth it? Our Quest has 170,000 miles on it, has had consistent and regular maintenance and still runs great. With a new lease on life for the air conditioning, were going to try and get a few more years out of it.
Good luck.
Phil Smith