Restoring A/C

[Glen C.]

I've got to restore the a/c in my 1972 and I'm debating whether to let a local shop do it or take on the project myself. It's not as much as a budget concern as the fact that I bought the car to work on and if it's reasonable for me to do the work myself I'd like to. The rub is I know virtually nothing about automotive a/c systems.

Everything appears to be present but the system is not charged and I don't know what condition the components are in. I did replace the wiring harness as part of a complete rewiring project a couple of months back.

I guess I'm looking for opinions as to whether this is something that a novice should take on and if so are there any reference materials beyond the AIM and shop manual I should get. Any advice would be greatly appreciated.

Thanks,

Glen

[Michael G.]

Re: Restoring A/C

Glen, I'm in the exact same situation as you and I am leaning towards getting a great deal of insight from this board, pick up manual on a/c systems of this era, and the equipment needed to proceed. We need to address the desiccant issue in the dryer. The container of this material breaks down and releases the pellets into the system. We need to clean them out and either replace or rebuild the dryer. I plan to draw a vacuum and see if it holds. If it does, I'm going to charge and test other components. Check the archives for other areas of concern like the build-up of debris in the housing that can cause issues. I think if we do our homework, ask for advise, and take our time we can do this. Mike

[Jim T.]

Re: Restoring A/C

Glen in addition to the information you have posted, is the present air conditioning system still installed as it left the factory, all connections connected? Does your compressor have a belt on it? If it does, does the compressor engauge or even operate now? There are members who post on this board that have much air conditioning experience. Local shops, charge a good amount of money and want to convert systems to 134. Do you want to stay with R12 that was the factory fill on your 1972?

[Glen C.]

Re: Restoring A/C

Mike,

Thanks. I think I'm going to take the same approach as you and take it on myself. I'll check the archives for info and also the desiccant issue. Please let me know your progress along the way.

Glen

[Glen C.]

Re: Restoring A/C

Jim,

I spent the morning looking things over. Everything seems correct and installed as it left the factory. The compressor has a belt on it but however does not engage. I am planning to stay with the R-12 refrigerant. I think that I'll take this on myself and jut go slow and ask questions.

Given the fact that the compressor does not engage does this indicate that the first order of business is to get it rebuilt?

Thanks,

Glen

Glen in addition to the information you have posted, is the present air conditioning system still installed as it left the factory, all connections connected? Does your compressor have a belt on it? If it does, does the compressor engauge or even operate now? There are members who post on this board that have much air conditioning experience. Local shops, charge a good amount of money and want to convert systems to 134. Do you want to stay with R12 that was the factory fill on your 1972?

[Larry M.]

Re: Restoring A/C

Jim,

I spent the morning looking things over. Everything seems correct and installed as it left the factory. The compressor has a belt on it but however does not engage. I am planning to stay with the R-12 refrigerant. I think that I'll take this on myself and jut go slow and ask questions.

Given the fact that the compressor does not engage does this indicate that the first order of business is to get it rebuilt?

Thanks,

Glen

I think we can help you through this. There is plenty of good info in the archives. You can search/check under my name, as I participate in most of the AC threads. You just need to realize that keeping an old AC system running on these cars is a labor of love. It is not always easy, but can be done by most.

I agree with staying with R12. The Chevrolet Factory Service Manual is your friend. EXCELLENT info on the AC system(s). The AIM may also help, especially is the old system is incomplete.

You first need to see why the compressor is not running. It needs 12 volt power /at the clutch. Check this first and see if power is at the clutch terminals. Also try and rotate the compressor over by hand. Should rotate easily, even if clutch is messed up.

There are still a few places where parts can be sent for repair and refurbishment. We even have a person on the forum that does top notch repairs to the A-6 compressors if that is indeed needed.

You will need a special toolset, and a refrigeration manifold and gage set. A good vacuum pump is also needed, although some find they can borrow or rent one when needed. You can also take an on-line EPA course that will certify you and allow you to legally purchase R12 refrigerant for your car. I (and many others) have done this and it is not difficult. Takes about 1-2 hours on the computer. However, many folks just do the mechanical work and have a certified tech evacuate and charge the system. Finding one still servicing R12 refrigerant can be difficult. I prefer doing it all myself. You can too.

Larry

[Tom L.]

Re: Restoring A/C

I'm going through a similar thing with my '72 but since I've been in the commercial rerigeration buisness I have an upper hand on the "referigeration cycle" part, the automotive a/c aspects are my weakness. As Larry noted making sure the clutch engages is one of the first steps. If you provide a 12v souce to the coil on the compressor you'll know if it works, simple. If it does engage and it won't engage using the cars controls there are other electrical problems. Look first at the Thermal Limiter, could be shot. If you have the service manual there's a good diagram for the system in it which is unique to '72 and '73, other years do not have the thermal limiter.

Once you've gotten the electrical system worked out it's time to see if there's any refrigerant in the system. Pretty easy, remove any cap from a service valve and use your fingernail to push the shrader valve (just like a car's tire) and see if there is any pressure. Hopefully there will be at least the SLIGHTEST bit of pressure. If there is that means you're in great shape, NOTHING got into the system. If no pressure it's still not a disaster as long as there are not huge leaks.

At this point you'll need a set of gauges so you can add pressure to the system, 20 psi should be more than enough. If you have some refrigerant (best choice) or a DRY source of air that would be good. If you don't have either you can use shop air since you WILL BE REPLACING THE DRIER and PULLING A DEEP VACUUM ANYWAY. You can accurately check for leaks for most of the system except for the evaporator itself and the compressor seal (likely candidate if the car sat for a long time, once they become dry of oil they tend to leak). For this I use an electronic leak detctor, halide torch or a liqiud soapy spray called Big-Blue. I'd guess you don't have any of these. Fortunately off the shelf Windex works pretty good. A big leak may hiss when sprayed but the hiss will stop quckly until you add more spray, a small one will make tiny bubbles. Small leaks are good but tough to find.

This should keep you busy. Good luck!!

[Glen C.]

Re: Restoring A/C

Larry,

As soon as this storm passes I'll check the clutch. I the meantime Ill spend time reading the archives as you suggest. Last night I started reading the factor service manual.
The compressor does rotate by hand. I knew about needing gauges and a vacuum pump but what other specialized tools will I need?

I'll take the online EPA curse you mentioned.

Thanks for the help

Glen

I think we can help you through this. There is plenty of good info in the archives. You can search/check under my name, as I participate in most of the AC threads. You just need to realize that keeping an old AC system running on these cars is a labor of love. It is not always easy, but can be done by most.

I agree with staying with R12. The Chevrolet Factory Service Manual is your friend. EXCELLENT info on the AC system(s). The AIM may also help, especially is the old system is incomplete.

You first need to see why the compressor is not running. It needs 12 volt power /at the clutch. Check this first and see if power is at the clutch terminals. Also try and rotate the compressor over by hand. Should rotate easily, even if clutch is messed up.

There are still a few places where parts can be sent for repair and refurbishment. We even have a person on the forum that does top notch repairs to the A-6 compressors if that is indeed needed.

You will need a special toolset, and a refrigeration manifold and gage set. A good vacuum pump is also needed, although some find they can borrow or rent one when needed. You can also take an on-line EPA course that will certify you and allow you to legally purchase R12 refrigerant for your car. I (and many others) have done this and it is not difficult. Takes about 1-2 hours on the computer. However, many folks just do the mechanical work and have a certified tech evacuate and charge the system. Finding one still servicing R12 refrigerant can be difficult. I prefer doing it all myself. You can too.

Larry

[Glen C.]

Re: Restoring A/C

Tom,

Thanks. I'm hoping I can get started this weekend. I'll check the clutch and when it's fixed start in on the items you gave me o check. I really appreciate the help.

Thanks again,

Glen

QUOTE=Tom Larsen (46337);695314]I'm going through a similar thing with my '72 but since I've been in the commercial rerigeration buisness I have an upper hand on the "referigeration cycle" part, the automotive a/c aspects are my weakness. As Larry noted making sure the clutch engages is one of the first steps. If you provide a 12v souce to the coil on the compressor you'll know if it works, simple. If it does engage and it won't engage using the cars controls there are other electrical problems. Look first at the Thermal Limiter, could be shot. If you have the service manual there's a good diagram for the system in it which is unique to '72 and '73, other years do not have the thermal limiter.

Once you've gotten the electrical system worked out it's time to see if there's any refrigerant in the system. Pretty easy, remove any cap from a service valve and use your fingernail to push the shrader valve (just like a car's tire) and see if there is any pressure. Hopefully there will be at least the SLIGHTEST bit of pressure. If there is that means you're in great shape, NOTHING got into the system. If no pressure it's still not a disaster as long as there are not huge leaks.

At this point you'll need a set of gauges so you can add pressure to the system, 20 psi should be more than enough. If you have some refrigerant (best choice) or a DRY source of air that would be good. If you don't have either you can use shop air since you WILL BE REPLACING THE DRIER and PULLING A DEEP VACUUM ANYWAY. You can accurately check for leaks for most of the system except for the evaporator itself and the compressor seal (likely candidate if the car sat for a long time, once they become dry of oil they tend to leak). For this I use an electronic leak detctor, halide torch or a liqiud soapy spray called Big-Blue. I'd guess you don't have any of these. Fortunately off the shelf Windex works pretty good. A big leak may hiss when sprayed but the hiss will stop quckly until you add more spray, a small one will make tiny bubbles. Small leaks are good but tough to find.

This should keep you busy. Good luck!![/QUOTE]

[Larry M.]

Re: Restoring A/C

Larry,

As soon as this storm passes I'll check the clutch. I the meantime Ill spend time reading the archives as you suggest. Last night I started reading the factor service manual.
The compressor does rotate by hand. I knew about needing gauges and a vacuum pump but what other specialized tools will I need?

I'll take the online EPA curse you mentioned.

Thanks for the help

Glen

Tools needed or nice to have:

1. Good quality manifold set for R12. Try and get a high quality one with 3ft. hoses. RobinAir is very good. Yellow Jacket is another good brand. MASTERCOOL is another. There are many.
2. Vacuum pump……around 1.5 to 2 CFM will do nicely. A 2-stage pump is nicer, but not mandatory.
3. Refrigerant Leak Detector (nice to have) Inficon TEK-MATE is an excellent one with low/reasonable cost
4. Basic compressor repair/rebuild tools like #22-1269 from Classic Tool Design (http://www.ctd4ac.com)
5. Chevrolet Factory Service Manual for your year Corvette. The more difficult to find Chevrolet Overhaul Manual is also nice to have, especially if any compressor work is in your plans. I would also get a Factory AIM for your year car. They are always handy.
6. I got my EPA certification from MAINSTREAM ENGINEERING (on-line). They are very good, but there are a few other places if you Google search for them (ie. EPA Automobile AC Testing). After this you can more easily purchase R12 refrigerant. You want EPA #609 MVAC Certification for motor vehicles. You can go "higher" if you thirst for knowledge.
7. A good dial thermometer for auto AC work. Very cheap. Small and accurate with a long stem to insert into the AC ducts.
8. Bottle or can of R12 refrigerant mineral oil. 525 cp viscosity. NAPA carries this. # TEM 209500.. Will need for adding oil or lubricating various o-rings and fittings.

Good places for advice or repairs etc:

Auto AC Forum at www.autoacforum.com They have a forum section and also an EXCELLENT Tips and FAQ Section. They also sell parts and o-rings, and other AC stuff. Store is called ACKITS.
Classic Auto Air in Florida Can rebuilt POA and Drier.
Old Air Products in Texas. Can also rebuild drier…..not certain about POA.
Just Google the above names for internet site addresses.
The archives in this NCRS Technical Forum

Hope this helps.

Larry

[Jim T.]

Re: Restoring A/C

Glen Cheatham a check for desiccant bag rupture in the dryer can be checked by removing the R12 supply line that connects to the expansion valve. Where the supply line connects to the expansion valve there is a screen/filter to stop continued flow of desiccant through the air conditioning system. The screen/filter and be removed and cleaned. When I did this I had bought a new filter/screen, do not know if the filter/screen is still available.

Not knowing your 1972's past air conditioning history you could check the expansion valve for desiccant blockage and if not any found do a vacuum pull (Auto Zone loans vacuum pumps) and install R12. Auto Zone loans gauges for 134 systems, I don't know if they have gauges for older R12 systems. If your 1972 has the dryer with a sight glass, you can read the charge of R12 using the sight glass. I have always added R12 to my 1970 just using the sight glass at the top of its dryer. Manuals will tell you how much R12 your 1972 takes.

I did a compressor replacement, accumulator replacement (dryer), vacuum pull procedure, compressor oil addition, and 134 installation with gauges using the "loan a tool program" from Auto Zone on another car and saved some money.

[Larry M.]

Re: Restoring A/C

Tools needed or nice to have:

1. Good quality manifold set for R12. Try and get a high quality one with 3ft. hoses. RobinAir is very good. Yellow Jacket is another good brand. MASTERCOOL is another. There are many.
2. Vacuum pump……around 1.5 to 2 CFM will do nicely. A 2-stage pump is nicer, but not mandatory.
3. Refrigerant Leak Detector (nice to have) Inficon TEK-MATE is an excellent one with low/reasonable cost
4. Basic compressor repair/rebuild tools like #22-1269 from Classic Tool Design (http://www.ctd4ac.com)
5. Chevrolet Factory Service Manual for your year Corvette. The more difficult to find Chevrolet Overhaul Manual is also nice to have, especially if any compressor work is in your plans. I would also get a Factory AIM for your year car. They are always handy.
6. I got my EPA certification from MAINSTREAM ENGINEERING (on-line). They are very good, but there are a few other places if you Google search for them (ie. EPA Automobile AC Testing). After this you can more easily purchase R12 refrigerant. You want EPA #609 MVAC Certification for motor vehicles. You can go "higher" if you thirst for knowledge.
7. A good dial thermometer for auto AC work. Very cheap. Small and accurate with a long stem to insert into the AC ducts.
8. Bottle or can of R12 refrigerant mineral oil. 525 cp viscosity. NAPA carries this. # TEM 209500.. Will need for adding oil or lubricating various o-rings and fittings.

Good places for advice or repairs etc:

Auto AC Forum at www.autoacforum.com They have a forum section and also an EXCELLENT Tips and FAQ Section. They also sell parts and o-rings, and other AC stuff. Store is called ACKITS.
Classic Auto Air in Florida Can rebuilt POA and Drier.
Old Air Products in Texas. Can also rebuild drier…..not certain about POA.
Just Google the above names for internet site addresses.
The archives in this NCRS Technical Forum

Hope this helps.

Larry

I just re-checked the ctd4ac website and I see that the #22-1269 toolkit is no longer offered, although it appears that most of the tools are still available individually. If anyone is interested, I would call and ask if they still have old stock or can make up a #1269 kit as a custom order. If not, I can/will provide the individual part numbers for ordering. Also, the ACKITS store has Mastercool A6 compressor/seal repair toolkits that are very similar to the Classic Tool Design kit………….perhaps even better, although likely more expensive.

I guess the demand for these old tools is just not there anymore.

Larry

[Glen C.]

Re: Restoring A/C

Larry,

I phoned and got a voicemail I left a message about the kit. I'll let you know what I hear.

Thanks,

Glen

[Edward J.]

Re: Restoring A/C

Glen, step one is as Tom says check to see if there is R12 in the system, before you take anything apart. low refrigerant will in the system will blow the thermo limiter which is really a fuse of sorts so the compressor does not run dry and cause a internal failure , which is something that would be very costly to repair. So the next step after that would be to check the thermo limiter, It has two spades that engage into two green wires and this is where the power to the compressor goes through. a simple test light can be used to see if there is power through the limiter. lets us know how you make out.

[Glen C.]

Re: Restoring A/C

Ed,

Thanks. With this storm moving out I'm going to get out in the garage this weekend a start checking things out. I'll check for R-12 and then the thermo limiter. I'll let you know what I find.

Glen