I have 2000 Expy w/68K and up until 2 weeks ago A/C blew cold. After a 30 minute traffic jam at 100F with A/C blowing I noticed it didn't blew as cold. It became apparent after 20 minutes. I thought I wasn't getting enough air through condensor or it was not too hot of an air as I have the dual elec fan set up. I thought maybe I need a shot of 134a, I finally found the low side connector yesterday and it was running at 70-80psi. Seems to high. Should I get some gages and check the high side as well? Seems like something is blocked or plugged. Any help is appreciated?
Thanks,
Rob

 

with that pressure it sound like your over charged. has anyone added refg. to your truck
also try cleaning your condensor if it gets to dirty it will not let the heat escape the refrigerant amd that can also raise your pressure
there any many things to look at txv valve pressure controls etc.

 

Never had any refrigerent added. The condensor is clean, no debris. I get good air movement with the dual 2500cfm fans.

 

it may not look dirty i bet it has a lot of road grime,dirt ect. i work on residential and commercial units and they dont look dirty put some condensor cleaner on there and you would be amazed what comes of . just the they are stationary units not driving down highways, sideroads, puddles get some degreaser spray it on let it sit for 10-15 min, rinse off it probably turn dark brown

 

I'll give it a try on the cleaning. You know I just swapped out the condensor on my 90 Towncar to one I pulled off a newer TC from a wrecked TC and sealed it good and hosed it down and had alot of dust/dirt come off before putting it on. Thanks, Rob

 

70-80 psi static pressure is somewhat normal depending on ambient temp. If the underhood was hot, I'd expect more.

What is the pressure with the compressor clutch engaged?

A set of manifold guages will always give the best data for diagnosing A/C performance concerns.

Steve

 

70-80 was with the A/C compressor running. It had been sitting for an hour in the garage. Yesterday I sprayed some cleaner/degreaser on the condensor and it cleaned up somewhat and did notice a quicker cool down, but I think I need to get some coil cleaner and reclean.

 

With a pressure reading of 70-80, you have one of the following issues:

Substantial undercharge
Defective compressor
Defective guage

Under normal operating conditions, low side pressure should drop down into the 20s and should not rise above 45 psi. Again, depending on ambient temps.

A high side reading would be extremely helpful.

Steve

 

I'll need to get a set of gages.

Thanks,
Rob