kook911 Posted June 18 Share Posted June 18 I am replacing all the parts except for the evaporator core and the hoses attached to the expansion valve. My question concerns the two spring parts located on one of the hoses and the drier. Some forums suggest these parts are unnecessary, while others say they are essential. Are these parts needed, or are they obsolete for the R12 system? Additionally, I have a gray plastic hose coming out above the expansion valve that is capped on my truck (highlighted yellow). What is this hose for, and do I need it for the AC to function properly? Link to comment Share on other sites More sharing options...
Gojira94 Posted June 18 Share Posted June 18 I'll let others more familiar with the valves answer that, but the gray line goes to the vacuum tank in the bumper. It's vital to all vacuum-fed doors and actuators in the heat/ AC system. One vacuum line from the engine to create the vacuum inside the tank, and lines going back out to things that need it (heat/AC doors, cruise control). Make sure your vacuum tank holds vacuum. Mine is seeping pressure and needs resealed along its seam. Link to comment Share on other sites More sharing options...
jdog Posted June 18 Share Posted June 18 Gray line to the canister, black line that is connected now to a vent needs to be blocked off as you don't have a heater valve. I would put the spring valves back in. Link to comment Share on other sites More sharing options...
Gojira94 Posted June 18 Share Posted June 18 46 minutes ago, jdog said: Gray line to the canister, black line that is connected now to a vent needs to be blocked off as you don't have a heater valve Jeez, I'm out of it. Just noticed it's 91+ and his vacuum tank is right there by the blower. Link to comment Share on other sites More sharing options...
AZJeff Posted June 18 Share Posted June 18 Those "spring parts" you show look like service port (filling) valves. Can you show a picture of where these are installed in your system? I might be able to answer better that way. Link to comment Share on other sites More sharing options...
kook911 Posted June 19 Author Share Posted June 19 4 hours ago, AZJeff said: Those "spring parts" you show look like service port (filling) valves. Can you show a picture of where these are installed in your system? I might be able to answer better that way. One valve spring sits on the drier side and the other sits in the hose. The flat face brass faces each other. This hose is connects to the expansion valve on the left side. If needed I can take them out as I haven’t put any 134a into the system, but right now they are in the lines. Thanks for helping with the gray lines. Hook up and good to go. Link to comment Share on other sites More sharing options...
MississippiComanche Posted June 19 Share Posted June 19 do you have the 4.0 or 2.5? I have the 2.5 and recently deleted the AC with non-AC bracket to get my truck to a functional state again. This hot @$$ weather has me considering buying all new AC parts and rebuilding it with 134a. Link to comment Share on other sites More sharing options...
kook911 Posted June 19 Author Share Posted June 19 6 minutes ago, MississippiComanche said: do you have the 4.0 or 2.5? I have the 2.5 and recently deleted the AC with non-AC bracket to get my truck to a functional state again. This hot @$$ weather has me considering buying all new AC parts and rebuilding it with 134a. i have the 4.0. Link to comment Share on other sites More sharing options...
eaglescout526 Posted June 19 Share Posted June 19 Hmmmm. I think I happen to have one side of this valve setup. I bet you it’s a restrictor that doesn’t dump the refrigerant into the dryer orrrr it doesn’t let mineral oil just flow easily into the dryer and cause a loss of oil. Just a couple guesses. I have a book I’m gonna go read that I have from AMC and see if it says anything. Link to comment Share on other sites More sharing options...
AZJeff Posted June 20 Share Posted June 20 I think some investigation into the operational theory of that version of AC is warranted before I can declare that valve's purpose. Time to dig around for the FSM for a 1987. Link to comment Share on other sites More sharing options...
zomeizter Posted June 20 Share Posted June 20 I converted my manche to R134A a few years ago and replaced everything but the condenser and evap. I dropped that valve you pictured when I performed a thorough flush job and could not figure out how to put it back in the correct arrangement so I omitted it. A/C is ice cold without it, maybe I got lucky... Link to comment Share on other sites More sharing options...
AZJeff Posted June 20 Share Posted June 20 I went digging through my 1990 and my 1987 FSM, and cannot see any details about what that valve does as it is related to the accumulator. In fact, they don't even really have a diagram showing the "theory of function" for that AC system, so that added port has me mystified. Maybe someone else who is more attuned to the older (and much less efficient) AC systems can explain what that friggin valve is for. Link to comment Share on other sites More sharing options...
Clay Perrine Posted June 22 Share Posted June 22 I am fighting this right now. I did a R134A conversion on my 88 Comanche, and it won't cool. I checked all the pressures on the system, and they are all correct. I have a friend that does Auto AC for a living (I am a retired Porsche Mechanic turned IT guy), and he helped me diagnose it. Seems the dryer is acting like an expansion valve and the refrigerant reaching the evap core is already expanded so no cooling. When I did the conversion, I put those parts in. My friend says I need to take them out and make it an empty fitting for R134a. That would explain the problem with the dryer acting like an expansion valve. And just a note... if you do a R134a conversion, you need to replace the low pressure cutoff switch with one that does both low and high pressure cutoff. R12 systems didn't need it, but the R134a can reach pressures that will blow out the burst disk on the side of the compressor. This switch is a direct replacement for the original one: https://www.summitracing.com/parts/VTA-11079-VUS It even plugs into the original wiring so you don't have to modify anything. You also have to replace the shutoff valves AMC used on the top of the compressor with ones that have R134a charge fittings. There is no clearance to put on adapter fittings. Link to comment Share on other sites More sharing options...
Salvagedcircuit Posted June 22 Share Posted June 22 3 hours ago, Clay Perrine said: You also have to replace the shutoff valves AMC used on the top of the compressor with ones that have R134a charge fittings. There is no clearance to put on adapter fittings. I thought this too, until I found out each lines rotates about the fitting on top of the compressor. you can easily fill up the low pressure size by just rotating the line. Link to comment Share on other sites More sharing options...
zomeizter Posted June 22 Share Posted June 22 3 hours ago, Salvagedcircuit said: I thought this too, until I found out each lines rotates about the fitting on top of the compressor. you can easily fill up the low pressure size by just rotating the line. 3 hours ago, Salvagedcircuit said: I thought this too, until I found out each lines rotates about the fitting on top of the compressor. you can easily fill up the low pressure size by just rotating the line. I installed adapters no problem but I have a "unicorn" 'manche... Link to comment Share on other sites More sharing options...
Salvagedcircuit Posted June 22 Share Posted June 22 2 minutes ago, zomeizter said: I installed adapters no problem but I have a "unicorn" 'manche... Ahh :/ Good luck with it. I'm still diagnosing my AC. It's been one hot summer so far! Link to comment Share on other sites More sharing options...
kook911 Posted Sunday at 09:00 PM Author Share Posted Sunday at 09:00 PM Update and even more problems. Did the switch and pulled vacuum on the system. Held at 27 mg for an hour. Then when I went to put the r134a into the system I could not get the system to charge. I made sure that I had power going to the compressor plug and got 12v. Then check the low pressure switch and got 11v. I jumped the low pressure switch just to make sure the compressor actually works and it kicked on with the low pressure switch jumped. So I went out and bought a new low pressure switch and still can’t get the system to charge. So I don’t know what’s wrong and I’m about to just pay a shop to get this ac working. Link to comment Share on other sites More sharing options...
zomeizter Posted 10 hours ago Share Posted 10 hours ago On 6/23/2024 at 4:00 PM, kook911 said: Update and even more problems. Did the switch and pulled vacuum on the system. Held at 27 mg for an hour. Then when I went to put the r134a into the system I could not get the system to charge. I made sure that I had power going to the compressor plug and got 12v. Then check the low pressure switch and got 11v. I jumped the low pressure switch just to make sure the compressor actually works and it kicked on with the low pressure switch jumped. So I went out and bought a new low pressure switch and still can’t get the system to charge. So I don’t know what’s wrong and I’m about to just pay a shop to get this ac working. Make sure the valves at the compressor (if equipped) are open by turning the square drives counterclockwise... Link to comment Share on other sites More sharing options...
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