Rear AC works on '97 Astro, front AC just recirculates inside air

astro
chevrolet

#1

The air conditioning has been weak in this van for several years. I have taken it to several places over the last 5 years to have it recharged, checked for leaks, compressor replaced. They always turned on both the front and back AC to recharge. This year I noticed that the back was cooler than the front and ran just the front for 10 minutes and then turned on the back. The front just recirculates inside air. After I turned the back AC off the temperature slowly warmed back up. What would make only the front AC quit working? There is only 1 compressor, accumulator, and orifice tube.


#2

Are you sure about that? Many vans from that era that had rear air had a separate system for the back refrigerant. It was usually located on the drivers side rear sidewall, right by the back doors.


#3

I have a Haynes manual and it indicates 1 compressor which was replaced last year. There is a separate cooling coil and blower motor for the front and the back. The repairman checked throughly for leaks. Given 10 to 15 minutes the back AC will cool down the van but at near 100 degree heat the first 5 minutes is too hot.


#4

With the ac on high front and rear reach under the hood and feel the larger of the 2 ac pipes that exit the plenum. Is it cold? If so the system is capable of cooling the air at the front and the problem would be in the duct/door system. If it is luke warm the system needs the pressure checked and the plumbing checked with an infra red thermometer by an experienced AC mechanic.


#5

The trouble here is not only are you unable to perform AC repairs (this is expected) you can not correctly describe the failure. You need an AC tech that is familar with GM dual AC systems and the places on the Astro where problems develope.


#6

Not sure what you mean about not being able to correctly describe the problem. Rear AC blows cold air, cold enough to cool the entire van in about 15 minutes. The front just recirculates the inside air. I have checked the vaccuum lines and replaced the one going across the engine. Outside air is not coming in on the AC setting. I have checked the pipes. Near the back AC, one line is hot and the other is cold. In the front one is hot and the other along with the accumulator are just barely cool. The system has been checked and charged in each of the last 3 years and the compressor repalced last after taking the van back to the shop and getting leak checks. I don’t mind paying to get it fixed but I am out at least $200 every year for the past 3 years.


#7

True I am not able to give pressures. Rear AC blows cold air, cold enough to cool the entire van in about 15 minutes. The front just recirculates the inside air. I have checked the vaccuum lines and replaced the one going across the engine. Outside air is not coming in on the AC setting. I have checked the pipes. Near the back AC, one line is hot and the other is cold. In the front one is somewhat hot and the other along with the accumulator are just barely cool. The system has been checked and charged in each of the last 3 years and the compressor repalced last after taking the van back to the shop and getting leak checks. I don’t mind paying to get it fixed but I am out at least $200 every year for the past 3 years. I also pinched off the hear hose under the hood to make sure the heater wasn’t re-heating the front air.


#8

Why have you not replaced the orfice tube? do you think this could not be the problem because the rear cools? this is where you are making your mistake.


#9

I know the repairman replaced the compressor last year because I could see part of that. I was trying not to look over his shoulder. I don’t know if he replaced the orifice tube or the accumulator. I don’t mind paying to get those replaced if it will fix it. I have read online AC questions and checked everything mentioned that I could do. Just for my own understanding, it seems like low refrigerant would make both front and back work poorly. Wouldn’t a clogged up orifice tube also make the front and back AC work poorly? The orifice tube and accumulator were the last ideas I got from all of the posts but it is another $200 probably and I didn’t want to guess. Thank you.


#10

There should be two orifice valves (fixed or otherwise), one for each evaporator. I don’t see how you could get two evaporators located some distance apart to work from just one orifice valve.


#11

Y

Tardis, you are almost 100% correct, pretty good for a non-AC tech, the issue is that in GM front/rear systems the rear unit is metered by a expansion valve. If the OP observation of the symptons are correct I would first just for reference see if any odd gague readings are present then do the recover and pull the orfice tube (up on the passenger side in a vertical tube with a crimp mark on it) and at least inspect it for debris and then make a decision on next direction.

Orfice tubes will ordinarly have some debris trapped in the screen, this is not a problem, it is where it gets to be too much that problems come. I am not too confident it is the orfice tube but we must take a look.

Perhaps a moderator can fix this, I had to change keyboards in mid-post,sorry


#12

I think that some of the confusion may be that I follow Ford’s terminology for parts. I consider what you are calling an orifice tube and what you are calling an expansion valve to be two different kinds of orifice valves. The tube is a fixed orifice, and the expansion valve is a variable orifice, usually varied according to the temperature that a sense bulb is exposed to.