Rear A/C problem

Cross posted in Astro forum:

98 astor rear ac no cold air. rear blower works fine.
front dash ac works fine.
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I'm having this same problem with my 2000 GMC Safari, and was wondering whether anyone has a solution/suggestion? My front A/C works fine. Picked up a Haynes manual, which doesn't go into much detail on troubleshooting.

Rear blower motor works, so Fuse and Relay are good. Don't feel any warmth or coolness from compressor lines runing to the rear evaporator. Coolant pressureis fine. Looking at the electrical schematic for the AC system in the Haynes manual, I noticed that there is a "Heater and A/C control valve solenoid" listed. It is shown in the schematic off of the rear heater control. I noticed today that my rear heater doesn't blow hot air (only ambient temp. but the front heater works fine- wondering if the problems are related through this solenoid control valve) and suspect that this solenoid may be the problem (after reading other posts on this forum- will have to try to "jump-out" the solenoid). If I am sucessful in jumping around the solenoid, would it be feasible to place a basic manual valve in the line, and use that to engage the heat in the winter and disengage the heat for the summer?

And, what is confusing me about the rear AC not cooling at all, is that the solenoid in question is listed in Haynes manual as both "Heater and A/C control valve solenoid". It doesn't make sense that this solenoid would control both rear heat and rear AC. Any thoughts? Any thoughts as to what may be the problem with my rear AC? Like I said, front AC works fine, I checked the coolant pressure, and it is fine (about 40psi on an 80 degree F. day). The rear A/C blower blows ambient, non-cooled air. Any help or direction is appreciated. I'm wondering whether there is some valve that is preventing coolant from reaching the rear evaporator, but Haynes says nothing about this (except the mysterious reference to the "Heater and A/C solenoid control valve")? Please Help!

Thanks for any thoughts.

BTW, in doing a cursory examination under the hood, I managed to break my 1/8" vacuum hose that allows switching of the vent/defrost/floor. Thanks to this site, I purchased some small diameter vacuum rubber line (86 cents), and spliced the broken ends together with no other clamps or glue (hope it holds!), and ran it over the air manifold. It seems to have fixed the problem. Thanks to everyone who previously suffered and labored, to help those of us following in your footsteps!

Get your self one of the old black light bulbs. Get under the van and check for leaks at fittings. The black bulb illuminates the ac fluid like
a liquid leak. This is what the air shops use. Pretty simple. It will look like
green spalsh marks. Pick a bulb up a walmart for 10 bucks. Had the same
problem. The o rings were blown out. Replaced them and recharged 3 yrs ago. No problems since.

Get your self one of the old black light bulbs. Get under the van and check for leaks at fittings. The black bulb illuminates the ac fluid like
a liquid leak. This is what the air shops use. Pretty simple. It will look like
green splash marks. Pick a bulb up a walmart for 10 bucks. Had the same
problem. The o rings were blown out. Replaced them and recharged 3 yrs ago. No problems since.