Chevy AC compresor blockage help - maybe manifold suction / discharge?

[solracem]

I'm trying to get my dash AC to work and keep blowing the gaskets on my compressors. Since the gaskets keep blowing and spewing out coolant, I'm assuming there is a blockage in the system.

I can blow through the condenser. So, I know the blockage isn't in there. And, I've also replaced the drier.

After I charge the system it will eventually blow the gasket on the compressor. I check the drier and there is no sign of it getting cold which makes me think that the blockage is somewhere between the compressor and the condenser. The hose from the compressor to the condenser is also free flowing. So, I think I've narrowed it down to the manifold suction and discharge service valves.

I did remove the shrader valves inside the service valves. So, it's not that. I'm wondering if anyone has a way to do away with these or if there is a trick to get them working properly?

Any advice/help is very much appreciated

[M & J]

Is this an R12 to R134 conversion? R134 fill is only 70% of the R12 charge by pound.

[solracem]

It is, however, I dont think that's my problem since the drier doesn't get cold at all. It makes me think these valves need to be removed. I'm just not sure how to go about making that work? 

[Rickf1985]

Have you checked for a plugged expansion tube or filter? What is the suction side reading when this happens?

[Rickf1985]

And those appear to be modified Ford valves from a York style compressor.

[solracem]

Rick - I'll check for a plugged tube/filter tonight and get a reading on the suction side as well. Can I get rid of the York valves? Do you know which valves should be on here?

[bluebird]

I'd just replace the orfice tube.

[solracem]

I'd just replace the orfice tube.

It doesn't have an orfice tube, just an expansion valve.

The low side is reading 28lbs

[Rickf1985]

The reading is a bit low but not unusual. I should have also asked about the high side. A clogged expansion valve would cause a negative reading on the low side so I don't think that is the issue. If you have over 350 lbs. on the high side at start up and only 28 lbs. on the low side then I would suspect moisture, too much oil in the system, or a clog after the test port. Like I said, that dryer does not look stock to me, where did it come from?
How long is it before it blows? The fact that there is pressure in the low side would tell me that either the system is flowing OR it is completely plugged up and the compressor cannot even pull any refrigerant in therefor the pressure stays static.

[solracem]

So, I was out there last night and was able to get the compressor installed without blowing the gasket this time 

Turns out the discharge valve needs to be halfway in while the suction valve needs to be all the way in. So, that problem is solved. However, I still don't have cold AC...  i??

The lines are getting cold, all the way to the expansion valve and into the box that contains the evaporator assembly. But, from there to my dash it doesn't blow cold. I'm at a loss.. Any suggestions??

Also, the solenoid on for the dash vents is broken or not getting enough vacuum. In order to get air to flow through there rather than through the bottom vents I have to squeeze it.

[Rickf1985]

Have you checked all the vacuum lines from the vacuum canister under the hood to the control on the dash and out to the blend door? The vacuum plug on the back of the controller on the dash will sometimes come loose.

[legomybago]

Also, the solenoid on for the dash vents is broken or not getting enough vacuum. In order to get air to flow through there rather than through the bottom vents I have to squeeze it.

Check the plastic spaghetti vacuum lines under the hood near the expansion valve area, there should be a vacuum can. Mine had some crusty spots. That's not going to solve your not cold air, you should have cold air coming through the defrost or floor vents now if the air was cooling.

[solracem]

I'll get a picture and post it for you guys to see the lines. I'm fairly certain there's an issue with the vacuum lines. Are the heater and AC vacuum lines the same or are they independent of each other?

[legomybago]

I think the vacuum just controls the vents? Im not 100% sure of that though. I know when I had a low vacuum issue (because of a melted vacuum line), when you were driving with the dash vents on blowing air, and you leave a stop light and accelerate, the dash vents would stop blowing air, the air would divert to the defrost or floor vents. As soon as you let up on the throttle and just cruise lightly, vacuum would build back up and open the dash vents again. This was my experience.

[Rickf1985]

Lego, that would indicate that the vacuum canister is not hooked up. Solracem, The vacuum controls that you are looking for are all on the control in the dash. There is one vacuum pot one the heater box for max air which closes off outside air and draws inside return only, that will not affect wheyher it gets cold or not. I was also thinking, it should default to the defrost setting if you have no vacuum. If it is anywhere else but defrost then you probably have vacuum but the plug is leaking or one of the bonded lines is pinched.

[Froggy1936]

This type of compressor did not come with service valves stock. Someone has installed them ! But Both service valves should be backed all the way out(blocking the service ports completely for normal operation )There should be no pressure or suction at either gauge connection for normal operation ! Frank

[solracem]

So, should I remove them and just get an adapter to connect the 134a service ports?

[Rickf1985]

The service valves should not cause the problem as long as they are open. They are a two way valve. all the way one way they are open for the system and closed for the gauges and all the way the other way they are closed for the system and open for the gauges. You should have them all the way open for the system and just cram them a bit in the other direction to get your readings and add refrigerant. Usually the service valves are on the lines, I am assuming this entire system has been changed around and all of the stock plumbing is gone? If the original service valves are still there then open these to the system and leave them alone at that point until you find the problem. Work off of the original valves. It may well prove that these valves are the problem but they should not be, they are a simple on and off valve. When the conversion was done the original service ports should have been converted from 12 to 134.

[bluebird]

It doesn't have an orfice tube, just an expansion valve.

The low side is reading 28lbs

If you are having high head pressure and low suction pressure, you may have a bad expansion valve. When you shut the system off, how long does it take to equalize?  The low side should come up as rapidly as the high side drops.  When you first start the system does the suction side go into a minus? It shouldn't.

[tmsnyder]

Considering that these systems are sensitive to particles and junk in the lines, those photos of your compressor laying in the dirt are concerning to me at least.  You aren't worried about getting sand or something in your system?

[expertrider]

I just went thru this issue... in my case, the thermal expansion valve was bad. Also, I replaced those r12 valves at the compressor with new r134a valves from eBay.. since everything was open, I replaced every o-ring in the system and blew everything out really well...made sure the flow was good, then vacuumed for several hours.. On my warrior 22, the air intake only has an outside air intake.. so, I sealed that and fabricated a recirculate air intake. It's often 100+ in south Florida here, so I didn't want to cool 100 degree air. I went with a new compressor and drier and now everything works good...