1973 Mach 1 a/c conversion

7173Mustangs.com

Help Support 7173Mustangs.com:

Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
The a/c on my 1973 Mach 1 is all original and I need to get the a/c converted over to the new type freon. Can someone tell me what all is needed to get it blowing cold air again? Thanks!
 
Joined
Feb 17, 2019
Messages
89
Reaction score
65
Location
Australia
My Car
1973 351c 2v fmx convertible
The a/c on my 1973 Mach 1 is all original and I need to get the a/c converted over to the new type freon. Can someone tell me what all is needed to get it blowing cold air again? Thanks!
Prior to disassembly fill a/c system with nitrogen/hydrogen tracer gas (if system has no gas in it) and leak test with a hydrogen leak detector. These detectors only react to hydrogen. This will tell you if there are any holes in the condenser or evaporator etc. if system has gas in it you can leak test with a normal leak detector but you would need to know what sort of gas is in it so as to use the correct detector. Your local a/c technician should be able to do this. Also check the electrical switching and under bonnet power to compressor. Sometimes the a/c thermostat can be faulty causing nothing to work. It is a simple fix.
Remove all the hoses and pipe assemblies and receiver drier (round black cannister by condenser in front of radiator).. Remove compressor. Remove the TX valve at the firewall. Flush evaporator coil (inside car) through the two pipes at the firewall after Tx valve has been removed with refrigeration flush and dry nitrogen Do the same for the condenser coil. If you know that your original compressor is good you can drain the old oil out and refill with ester or pag oil to the correct level. New R134a compressors have better bearings and seals in them to cope with the extra pressure of using R134a. I would recommend fitting a new York compressor or adapting a newer style compressor in. Fit a new R134a rated tx valve to the Evaporator tubes at firewall. Use new 'O' rings with some refrigeration oil on them. You can use the old hoses if you want and they are in serviceable condition. Just flush them out as per evap. and condenser. I would recommend new hoses. New hoses can be grafted onto old pipes using Lok Ring type fittings. i would recommend installing a high/low pressure switch onto the high pressure side of the system. Fit a new receiver drier. Evacuate and recharge the system
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
Prior to disassembly fill a/c system with nitrogen/hydrogen tracer gas (if system has no gas in it) and leak test with a hydrogen leak detector. These detectors only react to hydrogen. This will tell you if there are any holes in the condenser or evaporator etc. if system has gas in it you can leak test with a normal leak detector but you would need to know what sort of gas is in it so as to use the correct detector. Your local a/c technician should be able to do this. Also check the electrical switching and under bonnet power to compressor. Sometimes the a/c thermostat can be faulty causing nothing to work. It is a simple fix.
Remove all the hoses and pipe assemblies and receiver drier (round black cannister by condenser in front of radiator).. Remove compressor. Remove the TX valve at the firewall. Flush evaporator coil (inside car) through the two pipes at the firewall after Tx valve has been removed with refrigeration flush and dry nitrogen Do the same for the condenser coil. If you know that your original compressor is good you can drain the old oil out and refill with ester or pag oil to the correct level. New R134a compressors have better bearings and seals in them to cope with the extra pressure of using R134a. I would recommend fitting a new York compressor or adapting a newer style compressor in. Fit a new R134a rated tx valve to the Evaporator tubes at firewall. Use new 'O' rings with some refrigeration oil on them. You can use the old hoses if you want and they are in serviceable condition. Just flush them out as per evap. and condenser. I would recommend new hoses. New hoses can be grafted onto old pipes using Lok Ring type fittings. i would recommend installing a high/low pressure switch onto the high pressure side of the system. Fit a new receiver drier. Evacuate and recharge the system
I was hoping it would be much simpler than that because I don't have any A/C tools or equipment and no experience in working with a/c. If all of that needs to be done I will have to take it to a shop. I was hoping to fix it myself. Thank you for your input Mr. King!
 

giantpune

Well-known member
Joined
May 1, 2021
Messages
225
Reaction score
135
Location
GA
If yours is not blowing cold air now, you may have a leak. So fixing that would be the first thing to do. Find the leak and fix it.

On my 1969 tbird the previous owner paid a shop to convert the original AC it to the 134a. So under the hood its the original style compressor and all everything, but new style charging ports. It worked, but didn't work very long. It developed a leak and is no longer cold. I would suggest probably just buying a new compressor while you're at it, or at the very least, rebuilding your current compressor.

I do recall when you fill up an older AC system with the new refrigerant, you dont use the amount thats on the sticker. You need to get out your calculator and multiply by a factor to get the new capacity.
 

Hemikiller

Well-known member
Staff member
7173 Mustang Supporter Member
Moderator
Joined
Jul 12, 2010
Messages
3,765
Reaction score
1,033
Location
Killingworth, CT
My Car
71 Mach 1
65 coupe
I converted a couple of my old 80's Suburbans to R134 with nothing more then the conversion kit sold in most parts stores. I had a friend evacuate the system of R12, then I changed all the seals and o-rings. He vacuumed it for me to check for any leaks, and I refilled it on my own, as his equipment was old and only did R12.

That said, R12 is still available, but it's not cheap, but it may be less than the cost of converting to R134 and all the issues it may bring.
 
Joined
Jul 27, 2021
Messages
823
Reaction score
599
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
I was hoping it would be much simpler than that because I don't have any A/C tools or equipment and no experience in working with a/c. If all of that needs to be done I will have to take it to a shop. I was hoping to fix it myself. Thank you for your input Mr. King!
You will need at least a vacuum pump and gauges to work on your A/C. They are not too expensive, maybe $150 for both, and you will also need a conversion kit to R134. You need to vacuum the system for like 30 minutes with your gauges in place. After 30 minutes remove the vacuum pump and let the car sit for an hour or so and see if it looses vacuum. You vacuum gauge should have been close to 30 and if it does not loose vacuum, then your system should be sealed good enough to get a fill. If it looses vacuum I would recommend that you put some R134 in it with dye (you do not need to completely fill it), let the A/C system run for a while and turn it off. Get a UV light and the dye will glow where you have leaks. Hopefully it will be some o-rings that you can easily change or maybe a hose. If you cannot see the leak it may be in the evaporator. Any leak that you can see replace the components. Then vacuum it again with your gauges on for 20-30minutes, and let it sit with vacuum in the system for an hour or so and see if you have no leaks. If you still have a leak and it you can't find it it may just be in the evaporator, there are commercially available A/C leak sealers that are pretty good. I would try to use one before you go into trying to change your evaporator. Put the leak sealer in and fill with R134 to the recommended amount. There are conversion charts of how much R134 you need depending on how much R12 your system used to use. Check YouTube, there are a ton of videos on how to do this, but without a vacuum pump and some A/C gauges you will not be able to do it by yourself, at least not correctly.
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
If yours is not blowing cold air now, you may have a leak. So fixing that would be the first thing to do. Find the leak and fix it.

On my 1969 tbird the previous owner paid a shop to convert the original AC it to the 134a. So under the hood its the original style compressor and all everything, but new style charging ports. It worked, but didn't work very long. It developed a leak and is no longer cold. I would suggest probably just buying a new compressor while you're at it, or at the very least, rebuilding your current compressor.

I do recall when you fill up an older AC system with the new refrigerant, you dont use the amount thats on the sticker. You need to get out your calculator and multiply by a factor to get the new capacity.
As far as I know it hasn't blown cold air in at least 27 years! All I know is that everything is there and appears to be in good shape. The compressor is not locked up because I jumped it one day and it turned over good. I think I'm going to cross my fingers and see what happens. I thank you for the info and your reply!
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
I converted a couple of my old 80's Suburbans to R134 with nothing more then the conversion kit sold in most parts stores. I had a friend evacuate the system of R12, then I changed all the seals and o-rings. He vacuumed it for me to check for any leaks, and I refilled it on my own, as his equipment was old and only did R12.

That said, R12 is still available, but it's not cheap, but it may be less than the cost of converting to R134 and all the issues it may bring.
I think I'm going to try the same thing and hope for the best! If I can't fix it myself I can always take it to a shop. I found an old set of gauges and my a/c read zero so I don't believe it has anything in it. Thank you for your help!
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
You will need at least a vacuum pump and gauges to work on your A/C. They are not too expensive, maybe $150 for both, and you will also need a conversion kit to R134. You need to vacuum the system for like 30 minutes with your gauges in place. After 30 minutes remove the vacuum pump and let the car sit for an hour or so and see if it looses vacuum. You vacuum gauge should have been close to 30 and if it does not loose vacuum, then your system should be sealed good enough to get a fill. If it looses vacuum I would recommend that you put some R134 in it with dye (you do not need to completely fill it), let the A/C system run for a while and turn it off. Get a UV light and the dye will glow where you have leaks. Hopefully it will be some o-rings that you can easily change or maybe a hose. If you cannot see the leak it may be in the evaporator. Any leak that you can see replace the components. Then vacuum it again with your gauges on for 20-30minutes, and let it sit with vacuum in the system for an hour or so and see if you have no leaks. If you still have a leak and it you can't find it it may just be in the evaporator, there are commercially available A/C leak sealers that are pretty good. I would try to use one before you go into trying to change your evaporator. Put the leak sealer in and fill with R134 to the recommended amount. There are conversion charts of how much R134 you need depending on how much R12 your system used to use. Check YouTube, there are a ton of videos on how to do this, but without a vacuum pump and some A/C gauges you will not be able to do it by yourself, at least not correctly.
I found an old set of gauges and it read zero so I don't think it has anything in it. I can't find a conversion kit anywhere right now! Must be a China thing? Very good info here and I thank you for all your help!
 

giantpune

Well-known member
Joined
May 1, 2021
Messages
225
Reaction score
135
Location
GA
You will need at least a vacuum pump and gauges to work on your A/C. They are not too expensive, maybe $150 for both,
The harbor freight ones work great for this. You can catch the manifold on sale and the vacuum pump on sale, but never at the same time. :D
I wanna say if you get both on sale, you can get in under $100.

You do need to pay close attention to what you're doing. When pulling the vacuum and testing for leaks, exposed both high and low pressure sides to the vacuum. When filling the system, close the knob on the high pressure side so you dont pump in 150-200psi from the compressor to your poor little aerosol can with the plastic cap and make a bomb.
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
The harbor freight ones work great for this. You can catch the manifold on sale and the vacuum pump on sale, but never at the same time. :D
I wanna say if you get both on sale, you can get in under $100.

You do need to pay close attention to what you're doing. When pulling the vacuum and testing for leaks, exposed both high and low pressure sides to the vacuum. When filling the system, close the knob on the high pressure side so you dont pump in 150-200psi from the compressor to your poor little aerosol can with the plastic cap and make a bomb.
I'll try to be careful, thanks!
 
Joined
Feb 17, 2019
Messages
89
Reaction score
65
Location
Australia
My Car
1973 351c 2v fmx convertible
I'll try to be careful, thanks!
Recharging an a/c system properly with R134a, is done through an ambient temperature to high pressure relationship using gauges and thermometers.. When recharging an R12 system with R134a you generally put approximately 80% of R134a in compared to the original R12 quantity (one kilogram of R12 would convert to 800 grams of R134a). You must use R134a compatible oil as it will not carry the old 5GS R12 type oils. Real R12 has not been produced for many years and any old stock will have deteriorated over that time. A lot of fake R12 on the market is actually a propane based refrigerant.
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
Recharging an a/c system properly with R134a, is done through an ambient temperature to high pressure relationship using gauges and thermometers.. When recharging an R12 system with R134a you generally put approximately 80% of R134a in compared to the original R12 quantity (one kilogram of R12 would convert to 800 grams of R134a). You must use R134a compatible oil as it will not carry the old 5GS R12 type oils. Real R12 has not been produced for many years and any old stock will have deteriorated over that time. A lot of fake R12 on the market is actually a propane based refrigerant.
Great information! Thank you Mike
 
Joined
Apr 24, 2020
Messages
354
Reaction score
221
Location
Pittsford, NY
My Car
My all time favorite vehicle is our 1969 Shelby GT500
I did not read all of the receding replies as deeply as I usually do. So, I hope this is no repetitive. The refrigerant oil used in R-12 systems is not the same kind, or compatible with, the oil used in R0134 refrigerant systems. After you evacuate the R-12 you need to remove the old oil and use the correct R-134 compatible oil.

That said, for our 1969 Shelby GT4500, which also has factory A/C, I opted to keep the original A/C system in place. I was able to (and still can) find R-12 on ebay. It is a lot more than it was back in the 70s and 80s, but at least it is still available, although the writing on the outside is Japanese. All I know is it works. And the equipment used to pump a strong vacuum down on an A/C system, and the manifold gauge set, also still work nicely. Lucky for me I was able to get the Receiver/Dryer, Condenser, and TXV I needed for our Shelby, and after installing the new parts and pumping it down and later recharging the system, it is working beautifully.

We did install aftermarket A/C kits with R-134 in our 1973 Mustangs (both were non-AC cars originally). We selected kits from Classic Air. They also have a division that specializes in oem A/C equipment for cars. If yo run into a pinch, whether using R-12 or R-134, they have an excellent support group available via phone Highly recommended.


 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
I did not read all of the receding replies as deeply as I usually do. So, I hope this is no repetitive. The refrigerant oil used in R-12 systems is not the same kind, or compatible with, the oil used in R0134 refrigerant systems. After you evacuate the R-12 you need to remove the old oil and use the correct R-134 compatible oil.

That said, for our 1969 Shelby GT4500, which also has factory A/C, I opted to keep the original A/C system in place. I was able to (and still can) find R-12 on ebay. It is a lot more than it was back in the 70s and 80s, but at least it is still available, although the writing on the outside is Japanese. All I know is it works. And the equipment used to pump a strong vacuum down on an A/C system, and the manifold gauge set, also still work nicely. Lucky for me I was able to get the Receiver/Dryer, Condenser, and TXV I needed for our Shelby, and after installing the new parts and pumping it down and later recharging the system, it is working beautifully.

We did install aftermarket A/C kits with R-134 in our 1973 Mustangs (both were non-AC cars originally). We selected kits from Classic Air. They also have a division that specializes in oem A/C equipment for cars. If yo run into a pinch, whether using R-12 or R-134, they have an excellent support group available via phone Highly recommended.


Thanks for the information mrgmhale
 
Joined
Mar 28, 2013
Messages
37
Reaction score
6
Location
Oklahoma
My Car
1972 MACH I - 351C 2V - FMX
Good advice all around. I am faced with the same delima. This is what I am looking into. Any users out there?
I have converted several cars over the early years of 134, and each one was not as efficient as I would have preferred. Like yours, my components are factory installed, and when there is a leak, there is moisture that enters. Upon disassembly I discovered some age-old contamination.
You could also look at this:
Hoping too only do it once.
Seems like a reasonable way to go.

For personal use, Harbor Fright sells decent gauges and vac-pump. Use them once, save a buck, use them twice, etc. etc., they pay for themselves.

All feedback is welcome. Thank you
 
Joined
Mar 10, 2022
Messages
14
Reaction score
4
My Car
1973 Mach 1
Good advice all around. I am faced with the same delima. This is what I am looking into. Any users out there?
I have converted several cars over the early years of 134, and each one was not as efficient as I would have preferred. Like yours, my components are factory installed, and when there is a leak, there is moisture that enters. Upon disassembly I discovered some age-old contamination.
You could also look at this:
Hoping too only do it once.
Seems like a reasonable way to go.

For personal use, Harbor Fright sells decent gauges and vac-pump. Use them once, save a buck, use them twice, etc. etc., they pay for themselves.

All feedback is welcome. Thank you
thanks for the info!
 
Joined
Jan 1, 2012
Messages
8,223
Reaction score
963
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
R134 is not as efficient as R12. It requires a larger condenser and evaporator to match the cooling power of R12.
Duracool is a propane based refrigerant that is more efficient than R12, and has been approved by most countries. The US hasn't approved it because of volatility concerns in motor vehicles (that pack around a tankful of highly volatile and explosive gasoline). David (Carolina_Mountain_Mustangs) has tried it and really likes it. Individuals can order it directly online. You can read more about it here:
 
Top