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Patience, persistance, and a little sweet oil

JohnCarswell on Thu June 09, 2011 3:50 PM User is offlineView users profile

Year: 1972
Make: Chevy
Model: Surburban
Engine Size: 502
Refrigerant Type: none
Ambient Temp: 90s
Country of Origin: United States

I have a ’72 suburban 3-door. I am a hobby home mechanic. I have no automotive AC experience and only the most basic understanding of refrigeration. I started a do-it-your-self project and quickly got beyond my knowledge level. In this situation, ignorance is not bliss.

The AC was kind of cool when I bought the truck in 2007, but not very. The second summer I took it to Sears. They recharged the system with R134A…got vent temp down to 61 degrees. It gradually got warmer.

The second summer I got another recharge for another $150…same story.

I shop the LMC catalog. I saved up for the compressor upgrade. It’s a OldAir Products Pro6TEN Part Number 21-2201SH.

I took it to Sears to have them install it. The fellow in the shop told me it would be folly to install the new compressor without calibrating the POA valve, installing R134A compatible hoses, a new TXV, and a new filter/dryer.

I read a post from “Mitch” on your forum that showed a photo of a setup to calibrate the POA. I did it. It was easy. When I put 60 psi into the TXV the pressure in the POA was 28 psi. I adjusted it to 26 psi. (I live at sea-level on a barrier island on the SE coast of Georgia.)

The hoses from the compressor-manifold to the condenser and from the POA to the compressor-manifold are marked SAE 2064 “barrier”. I believe I can re-use them. The hose from the condenser to the TXV is not marked. I can buy the filter/dryer, the hose from the dryer to the TXV, and the TXV for the front evaporator from LMC for about $125.

The hoses to the rear unit are not barrier hoses. I bought new barrier-type hoses, 23 feet each, to snake through the chassis and body to the rear AC.

Here are my questions:

1)Do I need a new TXV for the rear unit? What kind? Where can I buy it?

2)Can I make hose-clamp connections that will hold R134A?

There are several clamps in this system. The hoses to and from the rear unit connect to tees in the lines from the POA to the evaporator and from the filter/dryer to the front TXV; they are installed with clamps. The old hoses were connected to the rear unit with clamps.

There are also two “extra” clamps on a ½ x 5/8 adaptor that someone in the past used to hook the original 5/8 rear hose to the tee in the hose from the POA (5/8 inch -- unmarked) into the hose (1/2 inch SAE 2064) going to the compressor. The 5/8 hose crimped to the POA u-tube is not marked, but it appears to have an inner wall so I think it is barrier type.

…fellow at the hose shop said he knew a guy that could crimp hose to o-ring type fittings for $20 each. I would need 10 crimps and some o-ring type tees and nips…I would like to save the expense if I can make clamps work.

3)If the clamps won’t work, can you recommend a place to ship all the old mess to for conversion to o-ring connectors.

Patience, persistance, and a little sweet oil can accomplish wonders...Dad

John Carswell

JJM on Sat June 11, 2011 2:10 PM User is offline

Sounds like you simply had a leak from the very beginning, my best is the shaft seal on the old A6 that would only cost a few dollars to replace. I doubt you need a compressor "upgrade" at all... the A6 is an extremely hearty unit and can go almost forever if oil level is properly maintained.

Given the age of the vehicle, you need to replace all the hoses, receiver dryer (go with XH7 or XH9), and o-rings (go with HBNR) - regardless of whether you're going with R-12 or R-134a. I recommend sticking with R-12.

The system should also be flushed, to ensure a dry system to add the proper amount of oil.

Barrier hoses aren't even an issue anymore, since most hoses from the 1993/1994 and prior R-12 era should be replaced, and they're all pretty much barrier now. It is been found that the mineral oil coating over the years in R-12 systems formed a pretty good "barrier" job, but now with age, the rubber should just be replaced regardless.

So in answer to your questions:

#1: TXV - front or rear - does not need to be replaced unless defective. They'll work fine with both R-12 or R-134a. The POA will need to be readjusted, and it looks like you've got that covered.

#2: You need a proper crimping tool for A/C lines - there's way just too much pressure and temperature differential and we're dealing with aluminum, which expands and contracts a great deal. The tools are not cheap, but there's a reasonable one available from this site:

71550 - Hydra-Krimp (Basic Crimper)

They go up from here.

You'll probably also need to replace your condensor if converting to R-134a, along with some fan enhancements. R-134a will also require PAG or POE (POE is preferred on retrofits), HPCO, and proper fittings, and labeling.


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