Okay I have an 1989 3.9 v6, D100, that I'm trying to get the air conditioner working on, this next week. I have a good compressor for it (which was missing when I bought it) and everything else is there and looks okay.

I also bought a new gasket kit and dryer. Bought some gauges and a vacuum pump that works with an air compressor.

I still need r12 to 134a conversion fittings, and I guess to find a sticker?



I notice there is a pressure switch on the low side that is like a round plastic disc by the firewall. I was wondering if the pressures are different from the r12 to 134a and if I will need to replace that switch??? The only one I can find is a -all metal one, labeled 134a at the parts store.

Also there is this piece on the low side line that connects to the compressor. The piece is on a canister. I don't know wtf it is. It kinda looks like a sensor missing a wire connector, but I didn't find a wire that would connect there. Better yet, here is a picture.

When the a/c works on these trucks, is it very good? Worse with 134a or about the same?

Any suggestions?

I really do not want to spend another Texas summer without air conditioning, am kinda excited. Thanks.

That piece is called a muffler. Besides changing the seals, a R134 system uses a condenser that flows better than the R 12 system. A R134 system uses a charge equal to about 2/3 3/4 of what a R12 system uses.

I looked up a new condenser, and its $150!! A/C for these trucks aren't cheap. Especially looking at what a new compressor and hoses go for!

From the pics of a new condenser, I do see how the tubes are parallel, as opposed to series like the unit I have. Seems, it would flow a lot better.

Is the muffler the piece hanging off the canister? Or the canister itself is called the muffler? If so, what is the piece that looks like a sensor?

Thanks.

If the system still holds a little pressure you could top it off with some R134A after you added some Ester oil (works with both R12 and R134A).

At least that's what I did on an '89 Taurus, put in two or three little bottles of Ester, then about 2 1/2 bottles of R134A.

The pressure switch wouldn't let the compressor run so the oil and the first couple of bottlesof R134A, I put into the low pressure side using a heat gun on the bottle. At that point the compressor kicked on and I added the remainder of the R134A with engine running, A/C on high, windows open, and a thermometer stuck in the dash vent. When it got below 38 degrees F I stopped adding the R134A.

This is "ultimate shadetree" mechanicing at its finest, not very elegant, but that A/C system worked through three summers like that.

PAG oil will not work for R12, don't use it on a mixed system.

There isn't an A/C shop who will work on a mixed refrigerant system, at least not to my knowledge. That means once you step out over that edge you can't go back. My '89 I knew was never going to see the inside of a refrigeration shop so I had at it.

The books are full of warnings about condenser insufficiency and compressor failures, these MAY happen but they didn't happen to me. I didn't change one other part from what I wrote above, except adding the R134A port conversion fitting to the stock port.

R.

PS: I hear the price of recycled R12 is coming down as demand ges down. Or smuggle it in from Mexico.

PPS: There are Federal laws against these procedures, so I am expecting the FBI to be breaking down my door at any moment.

Thats a pop off relief valve on the side of the muffler. I mixed 134 with 12 in my 89 cummins and had no issues

Ignore all the advice here and fix any leaks; then recharge with R-12.

Would an a/c shop have R12 on hand?



I plan to mount the compressor and put the new seal kit on, then vacuum it down, sometime this week.



Today I put on a new thermal fan clutch and blade. Decided to do the motor mounts while the fan was off. What I thought would be an hour job turned into like a 4 hour job. Only had a floor jack and a piece of pipe. Lesson learned. Don't do motor mounts without a engine hoist.

The hoses are often the weak link in old systems and they'll be much more so if converting to R-134. Good idea to have them rebuilt with barrier hose no matter which way you decide to go.

James, I would definitely use R12. Check the Dallas craigslist. There are some cans for sale on there for $15 to $25 per can. You will need a set of R12 guages as well. You will have fewer problems if you use R12.

I did a bunch of swaps at work years ago.Most we used the old hoses if they were decent.I like to change the O rings to the new ones.That and you run less 134 than 12.IIRC it 80 or 85 % of factory spec.Most cooled as good as the 12 did.I used ester oil in most conversions.Just dont add too much as it will affect pressure and it wont cool.Rocky

Some years ago I used one of those conversion kits to switch the air on my '84 from R12 to R134. It worked but not real well. Last year a bought a kit from Classic Auto air to replace everything from the firewall out to R134 compliant parts. Rotary compressor, mounts, condenser, dryer, hoses, etc. I now get 40 degree air out the vents! It works super.

Okay. So I put on the compressor and new gaskets.

I bought ester oil (and pag too just in case) but its not in a can, its in a bottle. How many ounces do I use on it, and where do I fill it at?

BTW

I've decided that I'm going with 134a because its readily available and if I have any leaks down the road I can easily find more. That's the only reason.

I'm also using all the original equipment. I understand its not going to work as well as it could.

I just need something to make it through the summer. Maybe by next summer I'll be in a better position to redo everything correctly.

The compressor was missing when I bought it. I have a used one mounted. I'm pretty sure there isn't any r12 remaining in the system.

After some searching, I have read I need to add the oil to the compressor itself. So I'll take one of the hoses off and add it.









I still need to know about the oil though. Do I use Ester oil because its an R12 compressor or PAG oil because its going to be 134a? And how many ounces do I add?

Thanks!

The factory V2 compressor has a plug in the sump that can be removed to check the oil level with a home-made dipstick. If you had the system open to replace the compressor there is no R12 remaining in the system but it's not the remaining refrigerant you need to worry about, it's the remaining mineral oil.

Ester oil will work with both R12 and R134.

That's good to know!

And thank you to the guy who told me that was a pressure valve. I would have never guessed that.




I used the ester oil, 8oz.

And today I did a vacuum on it, and found it leaks. So I put in a tiny bit of freon and found the leak. I just listened to where it hiss. Did that twice. Both leaks were at the new dryer. The gasket sets didn't seal good there. So I used o-rings and that worked great.

Filled with a three cans of r134 and the compressor wouldn't stay on still. Just cycled. Neither of the lines were cold. 150+ psi highside and 60+ until compressor kicks on then it went -30. I had a friend look at it and he said expansion valve is no good. So I'm going to replace that and try again.....

I will try and use green o-rings on the expansion valve if I can.

I'll let you guys know how it works out.

Thanks for all the good advice!

Just updating for anyone following or using the search button.




My a/c, now, works great after installing the new expansion valve. Also, I put a few ounces of pag oil in it. It was suggested to me by a guy that helped sort it out. I've also read that ester oil might not circulate with 134a. I haven't found my thermometer yet, its in a box somewhere.

I'm sure if I had used the correct condenser or R12, that it would be even better!

Thank you for the useful info!

Just wanted to add another update.

Since then ^^ I have added a r134a low pressure / cycle switch. Compressor stays on almost full time now.

I now have ice cold a/c, even in 100 degree heat, like today....

Without carpet my legs were sweating and its loud inside the cab. I remedied that with a $20 4ft x 6ft carpet that is thick. Much much quieter and cooler cab temps now.


Its awesome.

Thanks again.