'72 454 A/C oil and refrigerant capacity

[Randall K.]

I can't seem to find the total AC system oil capacity for my car in the AIM. The shop manual indicates 11 oz. I will be refilling with ester oil in preparation for R134a charge.

Can someone please confirm?

Also, how should I divide up the total fill among the compressor and other system components?

Finally, I understand that for R134a that I should use about 80% of the amount of R12 called for in the AIM. Correct?

Thanks
Randy

[Terry M.]

Re: '72 454 A/C oil and refrigerant capacity

Randy, I believe you will find the refrigerant oil quantities in the 1972 Chevrolet Service Manual and/or the 1972 Chevrolet Overhaul Manual. I am not sure which it is in, and quantities may be in both, or part in each. It will give you the amount of oil to add to the compressor if that unit is R & R, and the same for the condenser, evaporator and receiver/dryer. You will have to add up each of those numbers to get the total oil for the system.

It is my belief that you will not find the value for the oil in the AIM because each of those components were delivered to St Louis with the oil already in them.

Others here have more hands-on experience with 134a conversions than I have, so I will defer your last question to them.

[Larry M.]

Re: '72 454 A/C oil and refrigerant capacity

Randy, I believe you will find the refrigerant oil quantities in the 1972 Chevrolet Service Manual and/or the 1972 Chevrolet Overhaul Manual. I am not sure which it is in, and quantities may be in both, or part in each. It will give you the amount of oil to add to the compressor if that unit is R & R, and the same for the condenser, evaporator and receiver/dryer. You will have to add up each of those numbers to get the total oil for the system.

It is my belief that you will not find the value for the oil in the AIM because each of those components were delivered to St Louis with the oil already in them.

Others here have more hands-on experience with 134a conversions than I have, so I will defer your last question to them.

Agree with Terry. GM Service Manual shows

1. A6 compressor fill 6 oz (be sure to drain/remove any previous oil)
2. Evaporator fill 3 oz
3. Condenser fill 1 oz
4. Receiver/drier fill 1 oz
TOTAL ABOVE is 11 oz

I would add the oil to the compressor as stated above, add 2 oz to the receiver/drier, and the balance to the condenser. It will migrate to the evaporator and remainder of the system.

The genrally accepted charge of 134a is 80 percent of the R12 charge. For you this is about 2-1/2 pounds 134a. Use system pressures, the receiver/drier sight glass, and the inside duct temp to fine tune the 134a charge.

The POA valve should be adjusted for 134a versus R12. It is not mandatory, but a good idea. This requires a special test/calibration setup. Classic Air in Florida has this equipment, but you can also make it yourself. I can provides additional info if needed.....or contact them for assistance. Again, not mandatory, just recommended.

The GM Chassis Service Manual is your friend..............get a copy for your garage. Also, GM issued a service bulletin to their dealers regarding how to convert to 134a in the older systems. You should be able to "Goggle" it and get a copy. Or let me know and I can provide a link or scanned copy.

There is also a lot of EXCELLENT info available on the AUTOACFORUM at http://www.autoacforum.com. Checkout the Forum Section, and also the Tips and Frequently Asked Questions Section.

Larry

[Randall K.]

Re: '72 454 A/C oil and refrigerant capacity

Larry and Terry - thanks for the confirmation.

I have already had the POA valve serviced and recalibrated by Classic Air.

If you can provide a link to the GM service bulletin, that would be great!!

Thanks
Randy

[Larry M.]

Re: '72 454 A/C oil and refrigerant capacity

Larry and Terry - thanks for the confirmation.

I have already had the POA valve serviced and recalibrated by Classic Air.

If you can provide a link to the GM service bulletin, that would be great!!

Thanks
Randy

Try this: http://www.acdelco.com/pdf/appcat_bu...vice_parts.pdf. Also this

http://acdelcotechconnect.com/pdf/tsb/tsb_05D-114.pdf

I woud still use the Ester oil regardless of what is stated in the GM/DELCO bulletins.

Larry

[Terry M.]

Re: '72 454 A/C oil and refrigerant capacity

[Larry,
Thank you for a very detailed and educational post. You provided all the information I could not. Nice job!