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Expansion Valve Stuck Closed ???

Gerald K4NHN on Wed October 01, 2008 8:54 PM User is offlineView users profile

Year: 1982
Make: Chevy
Model: Luv
Engine Size: 2.2
Refrigerant Type: R-12
Ambient Temp: 78
Pressure Low: -20
Pressure High: 75

I finally got the Luv diesel back together. Replace the Receiver/Dehydrator, flushed the condenser, replaced the clutch on the compressor, added the 5 oz of oil back to the compressor like the manual called to do, vacuumed down the system and it held for over an hour with no loss. Put in 30 oz of R-12 in to the low side, but the low side has a -20 vacuum and the high side had 75 pounds. No indication of flow in the sight glass on the receiver. This is at the idle speed. I was afraid to rev it up, thinking that there may not be any oil making it through the system and back to the input of the compressor and would damage the compressor. The high side line was just a little warm and the low side was ever so slightly cooler that ambient air. It's been at lease a hour since I turned it off and the high and low side haven't equalized. There's still about 20 pound difference in them... The EV is inside the evaporator assembly and is going to be PITA to remove because at lease one connection doesn't want to come loose. I only tried one... The old compressor was frozen up, maybe because of no oil. I didn't find even an ounce in it totally. But I didn't see any trash when I flushed the condenser or the lines.

Now my next step?

Gerald K4NHN
Cayce, SC

Chick on Wed October 01, 2008 9:20 PM User is offlineView users profile

Did you flush all the lines? did you flush thru the expansion valve? if so you may have clogged it with debris.. Are you sure the drier is not clogged? may have to remove and see if it has flow thru it... Did you see any flow in the drier as you charged it? line going in and out of the drier same temp while charging?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Edited: Wed October 01, 2008 at 9:23 PM by Chick

TRB on Wed October 01, 2008 9:31 PM User is offlineView users profile

Also double check you have the hoses mounted to the drier with the proper flow direction. But that would equalize after time if they were back-wards. Sounds like a clog somewhere.

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Gerald K4NHN on Wed October 01, 2008 10:50 PM User is offlineView users profile

http://home.usit.net/~gcromer/luv-manual1.JPG

The line from the drier to the evaporator, I couldn't get apart at the evaporator, so I couldn't flush that one. I didn't try the outlet connection on the evaporator since the other one was frozen. The drier is connected correctly. From an earlier posting, remember I thought that there might be a blockage when I first opened the system. So I guessed that the E/V was maybe going to be stopped up. The high and low side pressures didn't come down the same. They didn't follow each other well. When I pull a vacuum, I can pull it on the hi side and the low side is real slow to come down and if I pull the low side first, the hi side is real slow to come down.. The only lines flushed were the short ones from the compressor to the condenser and the one to the drier. I didn't check the drier because I was afraid that I would put moisture into it. I didn't look at the sight glass as I was gasing it, only after I had it filed. I felt along the lines to see if I had any hot or cold spots along them, Nothing.

If I can get the outlet connection apart on the evaporator, what is the chance I can put some pressure in and back flush the blockage out or will that damage the E/V, evaporator. Evaporators are almost non existent for a LUV. I have an used aftermarket one but it has different connections on it.

Gerald K4NHN
Cayce, SC

HECAT on Thu October 02, 2008 10:17 AM User is offline

You could take line #41 off the filter/dryer and line #47 off the compressor. Blow a little dry compressed air (100 psi max) in line #41 and see if there is any air flow out line #47. If not , then the TXV is blocked or stuck closed. You could try and back blow through line #47 to see if it is a blockage (debris restriction) that can be cleared. You may need to regulate your air down lower to about 35 psi to do this as some TXV's will throttle closed when sensing back pressure. If a sense of comfort is not obtained with this process, the TXV is going to have to come out and be replaced. The frozen line may not be mean the evaporator has to be replaced as there must be place behind the dash (not shown in your picture) where the TXV attaches to the evap; maybe just a line replacement if it tears up the threads coming apart.

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FLUSHING TECHNICAL PAPER vs2.pdf 

Gerald K4NHN on Thu October 02, 2008 10:48 AM User is offlineView users profile

Hecat
Thanks for the very in-depth information...

Gerald K4NHN
Cayce, SC

Gerald K4NHN on Thu October 02, 2008 9:21 PM User is offlineView users profile

Well, not much luck today. We tried putting 100 pounds from the high side through the evaporator with no luck. Then we started with 35 pounds into the evaporator low side trying that direction and increased to 100 pounds with no luck either. We were able to get the high side connection apart with no trouble, but the low side just wouldn't move. I had been soaking it with Kroil the past couple of days planning for this. But it wouldn't move at all, I also tried the torch hoping that that would help, but no luck.

http://home.usit.net/~gcromer/Chevy%20Luv%20evaporator%20connection.jpg

I may try the small hole in the steel joint like on one of the other posts here to try and get some Kroil into the threads and see if that'll break it loose. You can see where the alum side was giving away from all the pressure. I would have liked to have had a gas wrench for the alum side but I didn't have one that large...
I may have to cut off the pipe just behind the joint. A old local AC guy said that he can weld on another end for me, that he does it on a regular basis. So much trouble.

Gerald K4NHN
Cayce, SC

mektek on Fri October 03, 2008 1:21 AM User is offline

On my nissan I had very similar symptoms. I tried to turn on the compressor at high revs to clear the blockage, but no luck. When I tracked it down to the TEV on the evaporator I found a particle of desicant had plugged the orfice. Once I cleared that, everything was fine.

HECAT on Fri October 03, 2008 3:41 PM User is offline

The method of revving the engine and trying to use the compressor may just drive a piece of debris further in and remember no refrigerant circulating, means no lubrication to the compressor. Many time the debris is too large to pass and will only come out the way it came in. This is why I suggested the back blow first.

Gerald, I am sorry to hear this did not get you any further toward cool air, and I agree from your attempts that the TXV is stuck or clogged real good, and will have to be accessed and replaced.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

Gerald K4NHN on Fri October 03, 2008 10:30 PM User is offlineView users profile

Helcat
I did manage to get the joint apart today. I drilled a 1/8" hole like the old post said and fluded it several times with Kroil. I had to hold the Alum side with a pipe wrench and wedge it with a couple of 2X4's against the fender well to stablize it and them put the muscle to it. It did strip off the first two theads on the alum fitting, but I was able to clean that up and have several threads still, so I think I'll have plenty to still hold it solid.. Three nut and the evap assembly slid righ out from under the dash...

I was able to get the valve out and looking down into the input with an otoscope, I can see what looks like corrosion around the spring and a little bit of trash that may be where the valve may open up. Can I unscrew hex screw in that port and maybe get some of that junk out.. If it's like averything else on the Luv I won't be able to find a new one. Got to start looking around.. This one has an extra line that goes from the body back to the low side line. Should that be open? I can't get anything through that line to either port. Can I heat or cool the bulb and maybe get the valve to open. Shouldn't there be some passage from the input to the output port to make the evaporator to even start cooling for things to start working and then the bulb would regulate the amount of freon into the evaporator.

I hope the pictures came through, that the first time I've tried that...

Gerald K4NHN
Cayce, SC

Gerald K4NHN on Fri October 03, 2008 10:40 PM User is offlineView users profile

http://www.autoacforum.com/forumimages/Chevy Luv evap joint.jpg

http://www.autoacforum.com/forumimages/Chevy Luv Exp Val 1.jpg

http://www.autoacforum.com/forumimages/Chevy Luv Exp Val 2.jpg

http://www.autoacforum.com/forumimages/Chevy Luv Exp Val 3.jpg

Trying again

Gerald K4NHN
Cayce, SC


mk378 on Fri October 03, 2008 11:07 PM User is offline

The valve should be fully open at room temperature and zero pressure. It is possible that the working fluid (R-12 in these old valves) has leaked out of the sealed sensor bulb and diaphraghm chamber. This would cause the valve to stay closed even though it is not clogged with debris. The only cure is a new valve.

The hex screw is probably an adjustment to set the pressure characteristics, if you unscrew it you must put it back in exactly the same position. Expansion valves are usually more generic than other parts.

Edited: Fri October 03, 2008 at 11:27 PM by mk378

Gerald K4NHN on Sat October 04, 2008 5:35 PM User is offlineView users profile

I'm already having trouble finding one that has flare connections on both ports and the equalizing line.

Gerald K4NHN
Cayce, SC

TRB on Sat October 04, 2008 6:09 PM User is offlineView users profile

31-10703

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Gerald K4NHN on Thu October 09, 2008 8:47 PM User is offlineView users profile

Here's an update on the Luv. I located an old shop that use to do AC work and stopped by as a shot in the dark. The guy said that he didn't have any new parts, but that after looking at the E/V he said that he thought that he may have what I needed. He came back with my old one and another one. His had the flare fitting but the small line came out at a little different location. So with a little bending of it I was able to get everything connected up. I charged ithe system back up and everything looked good. The next morning I noticed that one joint on the condensor had a little colored oil around it. I had to use Big Blu to even see the leak it was so small. But the dyed oil gave it away though. I tried to tighten it but it leaked worse then. So I pulled the system down again and used a little Nylog on it and that stopped the leak. It was putting out 42 degrees in about three miles of driving.

My thanks go to all of you that helped me on this project. And my neighbor is happy that I moved the truck from under their carport also.

Gerald K4NHN
Cayce, SC

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