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Astro front system blowing warm, rear system blowing cold

txturbo on Wed April 29, 2009 3:15 PM User is offline

Year: 1997
Make: Chevrolet
Model: Astro
Engine Size: 4.3
Refrigerant Type: 134a
Ambient Temp: 80
Country of Origin: United States

This van has the rear air. I recently replaced the compressor( because it wouldn't turn), the drier and the orifice tube. The van sat up for 3 years before I bought it. The orifice tube was clean so I figured the compressor wasn't locked up because of a failure of the compressor itself. Got it charged and working and it worked great for a couple of months. About a week ago I noticed it wasn't blowing cold air out the dash vents anymore so I figured I had sprung a leak and lost some freon. I put a temperature guage in the front and rear vents. The front was 62 degrees but the rear was 42 degrees. The compressor stays on and works normally. I know the suction line splits at the rear of the compressor and the high pressure side splits near the orifice tube. My question is....does the astro system have another orifice tube for the rear part of the system or do they share the one orifice tube? I don't seem to be getting good flow through the main evaporator any more. I'm wondering if the rear system has its own orifice tube and the front system orifice tube is clogged. Any ideas?

mk378 on Wed April 29, 2009 4:01 PM User is offline

In your typical American dual air, front has an OT under the hood, and rear has a TXV in the rear evaporator case. Sounds like it could be an air damper or reheating problem up front. See how cold the line leaving the front evaporator gets. If the evaporator is cold, the air should be too.

Chick on Wed April 29, 2009 4:25 PM User is offlineView users profile

Also check for leaks, when they leak, one will be colder than the other for a short time before you lose all cooling..Recover and recharge to factory specs, that will tell you for sure..Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

txturbo on Wed April 29, 2009 5:59 PM User is offline

The drier and evap lines are warm. I borrowed a buddies gauges last weekend and was going to check the pressures. When I connected the high side hose the valve stayed open and I lost most of my 134a. I replaced the fitting and pressured up the system with air and it held pressure. I tried evacuating the system but could get a good leak free connection with the borrrowed vacuum pump. I ran out of time, so I purged the system the best I could and recharged. It still works the same as before I messed with it. The last time I worked on it I was able to pull it down with my pump and gauges. I may have to wait until I get my equipment back and try again. I don't understand how the main evap. can stay warm while the rear one gets cold and works pretty good. If I had a leak and was low on 134a wouldn't the compressor begin quick cycling and wouldn't I lose cooling in the rear ac?

Edited: Wed April 29, 2009 at 6:00 PM by txturbo

GM Tech on Thu April 30, 2009 9:13 AM User is offline

The first thing I check on any system is how much refrigerant is in the system--- funny things happen when low on charge-- just as you describe-- so why mess around- pull the charge, weigh it- put the right amount back in- test it- see if cooling returns to normal, then if charge was low- leak test to find the leak, then repair the leak, pull a good vacuum and recharge to spec....

An a/c shop can do this for you with their recovery machine-- or you can fab together some bottles, dry ice, and scales yourself.....

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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