Dead end for me…😡

[Retired2014]

I just replaced most of my A/C components in my search for cold air. I replaced the TXV, condenser, compressor, filter, and flushed the lines and evaporator with solvent and lots of shop air. Some dirty stagnant oil in the evaporator, but no other surprises. Evacuated the system for an hour, holds vacuum overnight. Charged the system with R-12 ( my system is original with a York 210 compressor). My gauges read 80psi low side and 75 psi high side, engine running, warmed up, 85 degrees ambient. Pressures rise +/- 5 psi at higher rpm (2500). My old compressor showed similar behavior and the manual indicates a low High-side pressure with a high Low-side pressure indicates a blown head gasket. So on my old compressor, I replaced the head gasket and valve plate with no different outcome. Finally I replaced the compressor with a new one. Manual says if TXV stuck closed, I’d see a vacuum on the low side, so that’s not it. It seems like if it were the head gasket, a new gasket and valve plate would resolve this, but it didn‘t. Even a new compressor had no impact. My high side line is hot to the touch when running and the suction line is barely colder than ambient. If the system were undercharged, the manual says both readings would be low. No bubbles appear in the sight glass. So, my wise and experienced 71-73 owners, what do I try now? Any ideas from similarly afflicted vehicles?

 

[TheRktmn]

It's been 40+ years since I worked on A/C systems, but it hot high side and ambient low sounds to me like the expansion valve isn't functioning correctly. It may not be stuck closed, but it may not be opening completely either. A crimped capillary tube or bulb not placed correctly (tight against the line) will effect the valve also. Otherwise I would suspect a blocked evaporator or line.

 

[Steve McMahan]

Ok, a dumb question first. Are you sure the compressor clutch is engaged and the compressor is actually pumping? In any case, if the expansion valve was fully closed (I don’t believe that can happen) or fully open, stuck in either state, you should still have high side higher than 85 psi (That sounds like ambient temp). Baring the dumb question, it’s the compressor. There isn’t anything else to cause this situation. You likely have a bad reed valve. Unfortantly ,those are generally not included in any rebuild kit. I’m not sure you can get them, but a quick Google search will tell. Good luck. Steve

 

[Retired2014]

It's been 40+ years since I worked on A/C systems, but it hot high side and ambient low sounds to me like the expansion valve isn't functioning correctly. It may not be stuck closed, but it may not be opening completely either. A crimped capillary tube or bulb not placed correctly (tight against the line) will effect the valve also. Otherwise I would suspect a blocked evaporator or line.

It's been 40+ years since I worked on A/C systems, but it hot high side and ambient low sounds to me like the expansion valve isn't functioning correctly. It may not be stuck closed, but it may not be opening completely either. A crimped capillary tube or bulb not placed correctly (tight against the line) will effect the valve also. Otherwise I would suspect a blocked evaporator or line.

Thanks for your response! I did successfully flush the evap lines to and from the evap and the evap itself with solvent and air both. I guess I’ll flush the system components again and clean and reinstall my old TXV on my next attempt.

 

[Retired2014]

Ok, a dumb question first. Are you sure the compressor clutch is engaged and the compressor is actually pumping? In any case, if the expansion valve was fully closed (I don’t believe that can happen) or fully open, stuck in either state, you should still have high side higher than 85 psi (That sounds like ambient temp). Baring the dumb question, it’s the compressor. There isn’t anything else to cause this situation. You likely have a bad reed valve. Unfortantly ,those are generally not included in any rebuild kit. I’m not sure you can get them, but a quick Google search will tell. Good luck. Steve

Thanks, Steve. I was able to order a new reed valve plate and gaskets and tried that in my old compressor, with the same results pressure-wise, which led me to purchasing a new compressor. Yes, the clutch engages electromagnetically when the fan is engaged. Compressor sounds like it’s running and creates a drop in idle like it’s working and the high pressure outlet gets hot like it’s working. The manual offers basic guidance as attached.

 

[Steve McMahan]

You say hot? When it’s hot, what is the high side pressure? Is it the 85 you stated earlier? If it is, rebuilt or new, the compressor is not working. It’s basic physics. Ensure you are using good gauges also. If your not sure, try them on another vehicle. If they’re good, it’s the compressor. These are simple systems. Accepting everything you’ve said, only a failed compressor will give these symptoms. Steve.

 

[Steve McMahan]

This is from the Ford service manual. It does say a stuck open expansion valve can create low pressure on both sides of the compressor, so maybe service that before trying another compressor.

 

[Retired2014]

You say hot? When it’s hot, what is the high side pressure? Is it the 85 you stated earlier? If it is, rebuilt or new, the compressor is not working. It’s basic physics. Ensure you are using good gauges also. If your not sure, try them on another vehicle. If they’re good, it’s the compressor. These are simple systems. Accepting everything you’ve said, only a failed compressor will give these symptoms. Steve.

I’ll have to locate another set of R-12 gauges and try again. With the high side and low side pressures so close, it seems plausible the head gasket is blown, but with the original (once working last year) old compressor, the replaced reed plate and head gaskets in the old compressor, and the new (not rebuilt) compressor all being bad? It just seemed like I should be looking elsewhere. High side outlet is hot enough you don’t want to touch it but I didn’t measure the temp.

 

[Retired2014]

This is from the Ford service manual. It does say a stuck open expansion valve can create low pressure on both sides of the compressor, so maybe service that before trying another compressor.

View attachment 66347

The new replacement TXV was marked R134 when I received it and I called the supplier and they verified it would work on both 12 and 134. Other research of replacement TXV units also indicates these work on both 12 and134. I was skeptical and still am given your hypothesis of an open TXV valve causing both hi and low readings to be off.

 

[Retired2014]

I just replaced most of my A/C components in my search for cold air. I replaced the TXV, condenser, compressor, filter, and flushed the lines and evaporator with solvent and lots of shop air. Some dirty stagnant oil in the evaporator, but no other surprises. Evacuated the system for an hour, holds vacuum overnight. Charged the system with R-12 ( my system is original with a York 210 compressor). My gauges read 80psi low side and 75 psi high side, engine running, warmed up, 85 degrees ambient. Pressures rise +/- 5 psi at higher rpm (2500). My old compressor showed similar behavior and the manual indicates a low High-side pressure with a high Low-side pressure indicates a blown head gasket. So on my old compressor, I replaced the head gasket and valve plate with no different outcome. Finally I replaced the compressor with a new one. Manual says if TXV stuck closed, I’d see a vacuum on the low side, so that’s not it. It seems like if it were the head gasket, a new gasket and valve plate would resolve this, but it didn‘t. Even a new compressor had no impact. My high side line is hot to the touch when running and the suction line is barely colder than ambient. If the system were undercharged, the manual says both readings would be low. No bubbles appear in the sight glass. So, my wise and experienced 71-73 owners, what do I try now? Any ideas from similarly afflicted vehicles?

The new replacement TXV was marked R134 when I received it and I called the supplier and they verified it would work on both 12 and 134. Other research of replacement TXV units also indicates these work on both 12 and134. I was skeptical and still am given your hypothesis of an open TXV valve causing both hi and low readings to be off.

Update on A/C compressor.
I ordered a new York style compressor and installed it after flushing out its’ PAG oil fill and replacing it with mineral oil for R-12 systems. The new compressor would not build pressure. Turns out the new compressor’s head fractured on the maiden voyage after a successful R-12 charge. Note the yellow highlighted head crack.
Rebuilt my old compressor with a replacement valve plate and it is again blowing ice cold air. Gotta love R-12 refrigerant. Also cleaned and reinstalled my original TXV valve in addition to solvent flushing all components and lines, new condenser, dryer as well.

 

[c9zx]

I'm glad you got it sorted out. Thanks for posting the fix. It may help others in the future. Chuck

 

[Retired2014]

I'm glad you got it sorted out. Thanks for posting the fix. It may help others in the future. Chuck

Thanks. I never suspected the brand new compressor would have developed a cracked head after one 5 mile trip. That crack prevented the compressor from building pressure. Chinese reproduction… you get what you pay for as the saying goes. Lesson learned, don’t assume your new parts aren’t the source of the problem. Frustrating.

 

[basstrix]

Glad you got it sorted out. I'll be in your place, eventually, but it'll probably be while. I've saved a few cans of R12 from my mechanic days, but I see there are direct replacements available.

Wondering if you went with R12 or one of the alternatives?

 

[Retired2014]

I have an ample supply of NOS
R-12 and used some of that. Because I have that supply, I chose to stay with the old style York 210 compressor and not retrofit all the lines, parallel flow condenser, and Sanden style compressor (although the Sanden does have its’ advantages). I’m a fan of the original, ‘old school’ look of the York that I’ve stared at for 50 years now… and when the system if functioning optimally, I love that 33 degree air churning out of the vents.

 

[c9zx]

You won't see anything close to 33 degrees with a R134a retrofit. Chuck