A/C - Sticking with R12 but looking for help

[gable74]

I'm not an A/C guy but I know enough to be annoying. So I have a few questions and looking for some advice. I have spent a few hours reading old posts and questions on the subject which led me to more questions . Anyway here are a few I could use help with.

First, I am pretty sure everything as far as the A/C setup on my truck is factory original. The guy I bought it from said the A/C just blew warm air but since he had the truck in Upper Michigan he never really had a need for it anyway so he did not attempt any repairs. One of the first issues I noticed was the dry rotted vacuum hoses which I fixed so the passenger door flap as well as the heater valve were all working correctly. Just this small fix actually showed an improvement in temps of the A/C, but still not near where it should be.

Now what I would like to do is tune up the system. From what I gathered from other posts it would be something like this:

Replace O-Rings
Replace dryer
POA adjustment
Schrader valve replacement/adjustment
overall cleaning of parts and contacts
evacuate the system
test for leaks during vacuum
check/replace oil
charge with freon
Considering replacing the C6 compressor with an aluminum one

What I would like some help with are specifics of each of these steps and any I may have left out. For example, I do not know where all the O-Rings are or whats involved in the POA and schrader valve repairs.

I don't want to turn this into an r12 vs r134 debate. I have access to enough r12 to justify this path for now.

Any help would be great.

Thanks,
Jimmie

[davepl]

My only suggestion might be to run it on R134 first to make sure it doesn't leak, then put the precious R12 in it later.

I have a very slow leak that takes 3-4 months to empty the system, but I couldn't afford new R12 every 3-4 months, that's for sure! Of course I need to find the leak either way...

I ordered all the parts and an o-ring kit and if you start at one point and follow the lines and open every connection, you'll eventually find and replace every o-ring.

[hemi43]

Originally Posted by davepl

My only suggestion might be to run it on R134 first to make sure it doesn't leak, then put the precious R12 in it later.

That's a definite NO NO !! R12 uses mineral based oil, where R134a uses PAG oil.
The 2 should never be mixed. The OP should seek advice from someone in the trade and not on a chat forum, because there's some very bad advice given here that could cause irreparable damage.

[Andy4639]

In the world we live in today I would suggest the expert to look at it first. A good AC man can put a vacuum to it for a hour are so to see if anything needs fixing. Then they can charge it up and check it. If it has a problem they can pull it back down and fix it and charge it up again.

Then once the system is know good you can start doing 6 months checks on it and keep it in good working condition.

[Eddie H.]

What I would suggest is putting gauges on it first and see if the system has any refrigerant left in it. If it still has a partial charge, then there may not be much wrong with it.

[gable74]

Originally Posted by Eddie H.

What I would suggest is putting gauges on it first and see if the system has any refrigerant left in it. If it still has a partial charge, then there may not be much wrong with it.

Good idea!

[cdowns]

checkout the local yard sales I see the old overthecounter ones of r12 lots of times really cheap at a dollar or two each at that price id dump a few cans iinto the system and see if you get positive results at less than 5$ it wouldb worth the gamble

[Ed F]

What temperature air should a healthy AC put out? We haven't had any really hot weather here yet so I haven't been able to really test the AC in the Highlander. I put a thermometer on it today. About 80 outside and it was blowing 48.6 at an idle. I've gotta believe there isn't anything wrong with that.

[gable74]

So assuming I wanted to go through and tune up the system with new O-Rings, valves, and a dryer. Does anyone have links and part numbers to what I would need?

[drfloyd]

If it were me, I would definitely put the guages on it and see if there is a charge on it. If not, then I think you are at the point that you can go ahead with your refurb plan. Once that is done, you really need to dump some Nitrogen in and do a leak check to verify your work. The other thing that I haven't seen mentioned is that you need to evacuate the system before you charge it. Air is not your friend. At that point you can weigh in the charge and there is no guessing at all.

[gable74]

Originally Posted by drfloyd

If it were me, I would definitely put the guages on it and see if there is a charge on it. If not, then I think you are at the point that you can go ahead with your refurb plan. Once that is done, you really need to dump some Nitrogen in and do a leak check to verify your work. The other thing that I haven't seen mentioned is that you need to evacuate the system before you charge it. Air is not your friend. At that point you can weigh in the charge and there is no guessing at all.

Yup, definately going to throw the gauges on and see what I got first. Then if its empty I will move forward with the tune up. If its got some charge in it but is low, I will add some freon and see where i am.

Was hoping a few that have done this already could hook me up with some part numbers for the parts in case I have to go that route. O-ring set, heater valve, expansion valve, dryer, etc. I sent an email to classic air with the same question so I hope to hear backfrom them as well.

Thanks

[buddylee]

With a discharge temp of 48 degrees you are running fine.
Run with it

[F.A.A.benny]

As mentioned above. put the gauges on it. If it has a partial charge then top it off. If that system is original, never been opened , and doesn't have a leak then you don't necessarily have to go through it at this point unless you really wanted to.
Now as for your list of things that that need to be done and parts you would want to buy when going through your system: First off yes you will definitely get a response back from Classic because they will want to sell you pretty much everything and at a hefty price.
You get orings anywhere from ebay, autoparts stores, harbor freight, auto ac shops, hose supply houses, etc. I buy mine in bulk. Same with Schrader valves and there is no adjusting them. Drier from ebay, rock auto, local auto parts stores. Poa doesn't need to be recalibrated if staying with r12 and wouldn't change the exp valve either. I would apply the following If going through the parts: I personally would flush and pressure check the evap and the condenser. You can new hoses from Old air products, the truck shop or lmc. They sell them at a fair price. But since you are staying with r12, your original hoses may work just fine. Putting the system in a vacuum can tell you if there is a leak but not so much in terms of where it is. To give an example, I restored pretty much the entire system of a truck a little while back. Put the system in a vacuum and it wouldn't hold. Everything was new/ rebuilt/ restored. All fittings were tight. Had to charge the system with nitrogen. Sprayed soapy water on all fittings and there was nothing wrong with the system. It was a bad coupler oring on the robinair machine. If you flush the system use mineral oil again. Local hvac supply houses should have it or you can get it on ebay?/ amazon, or even through google's search https://www.google.com/?gws_rd=ssl#q...l+oil&tbm=shop Aluminum A6 replacement compressors are available from quite a few vendors. I wouldn't pay more than $300. Here is just one of them. http://www.ebay.com/itm/GM-A6-Replac...-/151803236077

[rsgt]

If staying with R12 is it ok to put ester oil in the compressor?

[F.A.A.benny]

Originally Posted by rsgt

If staying with R12 is it ok to put ester oil in the compressor?

You can because its compatible but I would use mineral oil if staying with r12

[gable74]

Thanks everyone. Good news is there is pressure in the system and I can see fluid in the sight glass. There are bubbles in the sight glass so I am hopefull its just low on freon and all it needs is a charge.

On a side note as I was looking the system over I noticed something odd about the heater valve. Even when under vacuum (the valve should be closed under vacuum) the hose behind the valve was very warm. Is this normal? I would have thought with the flow being stopped by the valve it would not be warm. If this valve is bad it could also be part of the issue. The valve looks pretty rough so I am going to pick up a new one either way and put it on.

I am going by the house to pick up my gauges tomorrow so I can see just what the pressures are and go from there. Does anyone know off the top of their heads what the high/low pressures should be? Thanks for everyones input.

[SS Tim]

There is a lot of good information here and some bad. Unless you are properly converting to R134 keep it well away.

Though the information is dated, the factory chassis service manual has a good section on the four season A/C service and repair proceedures.
It also includes a performance test, @2000rpm with a 80* ambient temp you should see 38-41* with the factory fill of R12 (72 fcsm 1A-20).

Most of the manuals on pdf are linked in my signature below RTFM.

[gable74]

Thanks.

So where I am located I should see 29.5 on the low side and 185-195 on the high side if the OAT is 80*.

[davepl]

Originally Posted by SS Tim

There is a lot of good information here and some bad. Unless you are properly converting to R134 keep it well away.

Can you expand on that? I never though of R134 as "contaminating" R12, but you make it sounds like that's the case. Explain?

Not challenging, just asking because I don't know.

[RichardJ]

>>R12 uses mineral based oil, where R134a uses PAG oil.<<

You can't flush oil out of a compressor. You can drain it, but you can't flush it. When switching from R12 (with mineral oil) to 134a, you drain the old oil and replace it with Ester Oil. You flush the hoses, condenser and evap. You replace the dryer, if for no other reason than it will have mineral oil in it that you can not flush.

The Ester oil is compatible with any remaining mineral oil, PAG is not.

If a new compressor is sold for 134a and has PAG oil in it, then you would always use PAG if repairs are made.

[SS Tim]

Dave, All I can go on is mostly what I learned through Saturn. In the later 90s is was fairly common to "upgrade" an early R12 Saturn to R134A simply due to the cheaper R134A. We had a specific factory manual (if I have a copy I don't know where to begin to look) that outlined the simple steps for a conversion and tables for converted cars. These did not exactly match the R12 nor the factory R134A cars IIRC. In doing the changeovers basically it was only the hoses and seals the needed replacement to be compatable. We were advised (in the manual) the receiver dryer was large enough for the existing mineral oil charge to settle out when the PAG charge was added to the system. The claim was the system was designed anticipating the changeover and most existing parts worked with R134A. In practice worn compressors did not like the PAG and both compressor and THX valve issues were common post retrofit. One thing both Saturn and my NAPA sponsered retrofit class stressed was it is a one way conversion, that IIRC is due to the insolubility of PAG into R12.

[davepl]

Thanks!

[gable74]

It probably got lost in the conversation but what is the answer on my heater valve question a few posts back? Should the hose still be hot behind the valve if its closed?

Originally Posted by gable74

On a side note as I was looking the system over I noticed something odd about the heater valve. Even when under vacuum (the valve should be closed under vacuum) the hose behind the valve was very warm. Is this normal? I would have thought with the flow being stopped by the valve it would not be warm. If this valve is bad it could also be part of the issue. The valve looks pretty rough so I am going to pick up a new one either way and put it on.

[MARKDTN]

I would add another heater valve to turn it off in summer. Water leaking past the old valve is a big problem with these early 4-season systems.


OP-I know you are not going to, but for future readers of this: I would also echo the do not go to 134 and back to R12. That is a recipe for disaster. In my experience, even converting to R134 you have a better chance then not of eating the front seal of the compressor on either an A6 or R4 compressor. The Saturn (and other similar era) compressors mentioned do better with swaps than either an A6 or an R4 as far as not eating seals. Also as mentioned, the oils are not compatible.

[WorkinLonghorn]

Just a note. I have experience with commercial AC systems and some knowledge about Vehicle ACs and I wanted to point out that the correct way to leak-test a system is to use pressure, not vacuum. The shop I use to test systems uses 300 PSI of nitrogen.

If you use vacuum, you are using 14.7 PSI. and if there is a leak you are sucking air and moisture into the system which is always bad.

You can also use a Halogen leak detector ( around $30 on e-bay etc.) on a system pressurized with Freon. WL