AC question

[HowieE]

Anyone know were the metering valve for the rear AC is located in a 97 Sub?
I have a very high temperatures, 80 F, on the suction line coming back from the rear system and generaly low cooling in the truck. The line from the front is within reason and the pressures are close. If the superheat is what I am feeling on the scution line I am thinking the metering valve is clogged.

[diesel65]

Hi Howie,
The expansion valve is located inside the rear a/c box, Your biggest problem will be if you want to service either the valve or the evaporator is to undo the two joints under the truck.
I have replaced rear lines and wind up replacing the evap and the expansion valve because I could not break the connection loose.
Do you have rear heat? If you do then you will need to disconnect the rear heater core.
Just in case you didn't know, the orifice tube for the front a/c is located under the passenger side battery.

[charliepeterson]

I would evacuate,vacuum and recharge to a weighed charge before getting into the rear unit. These systems don't tolerate anything but a full charge on a hot sticky day.

[markelectric]

As it was explained to me, That orifice is the smallest in the system. Most of the GM compressors are tefelon lined. when the lining comes off the orifice is the catch point. The rear air blowing heat was the first clue to my system going out. It may be advisable to have someone experienced with split systems to take a look at it. Mine required a compressor and a condenser and a bunch of small parts, all due to tefelon contamination.

[rjschoolcraft]

After the first failed (grenaded) compressor, I had the local Chevy dealer replace it. I had no experience with R134. Big mistake.

The mechanic just replaced the compressor... didn't clean the lines or replace the drier (accumulator, that aluminum canister near the firewall). Needless to say, the new compressor grenaded in about 16 months. I replaced this one. After the first was replaced, the rear air did not work...only blew hot air.

I tore into it when I replaced the compressor and found the expansion valve at the rear evaporator clogged with debris from the compressor failure. Absolutely no circulation! I disconnected the lines from the front and rear and flushed everything out and blew out the condensor. The orifice tube in the front was clogged as well. The replacement expansion valve has a screen on it to help prevent clogging...the old one did not.

I replaced the drier, recharged and everything works great now. I cut the old drier apart and found it full of debris.

The expansion valve for the rear is mounted to the evaporator and is fairly easy to replace...once you get to it. It's a big job to tear into that back air box. By the way, don't try to find the expansion valve mentioned or shown in the service manual. According to the book, it doesn't exist, but it is there.

Good luck.