1991 Mustang GT w/ R12 - need help

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fastsvo
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1991 Mustang GT w/ R12 - need help

Post by fastsvo »

Hi Everyone,

I have a '91 5.0 with 62k original miles. About 12 years ago, I had the system vacuumed and recharged with R12 and 4oz of mineral oil was added (it had Freeze 12 before). Worked great! That is until COVID hit and I stopped driving the car. Now, the system doesn't blow cold and I am assuming it's empty (more on that later). I can see dirt around the front seal of the Denso 6P148A compressor, so again, assuming it's leaking out of there.

I cannot find a shop local to me (SoCal) that wants to even touch this thing because of the R12. Yes, I do have more cans of this stuff and I want to use it :)

So, I am stuck with trying to learn and service this car myself and hopefully be able to pull this off with the help and knowledge shared here. I would like to start with the basics and just simply diagnose the car with a set of gauges, an air compressor and soapy water. I will need some guidance here.

I was able to borrow a set of 134/410A gauges.

Would this be sufficient? Can someone please point me to a set of adapters so it can work with my R12 charge ports?

When removing the cap on the high side, it started to hiss out freon, so I quickly closed it back up. I understand the caps are the the primary seal here, but should have that happened?

How bad of an idea is it to turn car on and engage the AC while diagnosing this? Wouldn't it further ruin things in the system?

Thanks for your help!
Last edited by JohnHere on Thu Sep 01, 2022 1:45 pm, edited 1 time in total.
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tbirdtbird
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Re: 1991 Mustang GT w/ R12 - need help

Post by tbirdtbird »

"About 12 years ago, I had the system vacuumed and recharged with R12 and 4oz of mineral oil was added (it had Freeze 12 before)."
This has come up before.
I was just reading a case like this in the archives:
messageview.cfm?catid=2&threadid=22464
Freeze12 is an advertising gimmick making you think you have something legitimate in your R12 system. It is actually a blend of R134 and R142. It has absolutely nothing to do with R12. Notice the letter "R" is lacking in the designation. There are oil compatibility problems with the mineral oil in your system.

My advice is to flush the entire system, remove the comp and flush that, and start fresh. When you get to that point come back and we can advise you further. There are pointers on flushing on this site in the Flushing Forum, and the flush gun and flush solution can be obtained from Tim, the owner of the forum, at ACKits.com, at reasonable cost. I would also replace the comp and filter drier, again available from Tim at reasonable cost

You will need to add the proper amount of R12 and mineral oil once your system is back to bare metal.
Have to wonder why someone installed Freeze12 if you had a supply of R12
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fastsvo
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Re: 1991 Mustang GT w/ R12 - need help

Post by fastsvo »

The car currently has R12 and everything was flushed out 12 years ago. Now, it’s time to do it all over again, except I need to take the lead on this :/.
tbirdtbird
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Re: 1991 Mustang GT w/ R12 - need help

Post by tbirdtbird »

OK, I am glad we got that cIeared up. We are happy to help.
"I was able to borrow a set of 134/410A gauges".
You are looking for R134 to R12 adapters, which are available easily via internet search. Not sure if Tim has them. R12 uses 1/4 male flare fittings, R134 uses 1/2" Acme fittings

I would still advise replacing the comp and filter drier

"How bad of an idea is it to turn car on and engage the AC while diagnosing this? Wouldn't it further ruin things in the system?"
I would not do this, especially if the system is empty. If there is still any R12 in the system, I would use an electronic leak detector (sniffer) to check for any leaks before going further. Barring that you can use soapy water but that method is not as sensitive as the sniffer. Also, the electronic sniffer can be used in the evap drain from under the car, but the soap bubble trick does not allow you to do that.
If the system is truly empty, then you can puff in a small amount of R12 or even Freeze-12 if you have any left over, just enough to get to about 20 psi on both the hi and lo side and then proceed with a sniffer, etc. You can also use dry nitrogen but then you will have to use soap bubbles. The last resort is shop air, and bubbles. But shop air has a very high water vapor content and you will need a longer vacuum time to get it all out.

You have a leaking schrader valve core which can be replaced with a schrader tool easily. Or maybe it just needs to be snugged up. Such a core resembles a tire valve core, but has a better seal.
You will have to recover the R12 to evacuate the system before you open it up to change the comp and FD. The core can be changed out then. They are also available on line all over the place. There is a so-called "hot swap" tool for changing schrader cores on the fly without evacuating the system, but you have to open your system anyway.
I usually check the snugness of schrader cores whenever I work on a system, but do not over tighten you will destroy the seal.

Some of your hose clamps may be loose, some of the hoses may be aged and brittle (30 yrs old) and oozing refrigerant. Leak detection will help with all that.

Sounds like your first order of business is to get the gauge set adapters.

As an aside, I am confused that you say your gauges are for R134/R410.
As stated R134 uses 1/2" Acme fittings, while R410 uses 5/16 SAE fittings. So I am not sure exactly what fittings you now have on your hoses.
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Cusser
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Re: 1991 Mustang GT w/ R12 - need help

Post by Cusser »

In Phoenix, there are shops who service R-12 systems as recently as a couple of years ago; even the local ASE shop I use checked my 1988 Mazda truck for leakage and filled it a few years ago when I wanted to know the oz. R-12 in it.

I'd be real surprised if there are no shops in S. California that still service R-12; I'd contact AC specialty shops, vintage car clubs, etc.

Myself: I still have R-12 gauge et as well as R134a set, and 1991 Mustang likely needs the smaller Ford-type adapter for the smaller high side fitting; I use such adapter for my 1988 Mazda truck, and of course GM/Toyota use a slightly different adapter.

Most vacuum pumps -including the loaner ones from Autozone - have fittings for both R-12 and R134a; the loaner service gauge sets are R134a so you'd still need R-12 adapters (assuming such stuff is allowed in California).
tbirdtbird
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Re: 1991 Mustang GT w/ R12 - need help

Post by tbirdtbird »

Some good suggestions. Another idea is to get on to the MACS (Mobile Air Climate Systems) website and you can get a list of MACS certified AC shops in your area. There is a link to click there for that.
For those that are unaware, MACS is a high-powered Mobile AC certification process and these guys are highly trained. At least one of the consultants on this board is MACS certified (JohnHere). A MACS shop IMO is more likely to be able to help you out.
When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com
fastsvo
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Re: 1991 Mustang GT w/ R12 - need help

Post by fastsvo »

Thanks for the replies!

I guess the link to the gauges in my original post was stripped away. Let's try this again: .From what I can tell, this gauge set's low side port is 1/4” flare, which should work on my low side port. The high side is a 1/2” ACME fitting. I think I will need an adapter for the high side - 3/16"?

With respect to the valve core removal tool (on the high side), it seems that a 3/16 fitting is hard to come by, but those 1/4" tools can be used with the appropriate adapter.
Of course, I am not 100% certain if these tools or sizes I am posting are correct.

I have contacted a lot of local shops, only to get either turned down or referred to someone else, who then still couldn't help me. A lot of these shops no longer have the equipment (or it's not working). I have been looking for a "Journeyman" A/C guy, who might be able to help me out, but still searching.

Yes, I need to figure out and get the correct gauge adapters and hook them up. I found a 4 Seasons reman compressor w/o the clutch and I am leaning towards this part.
tbirdtbird
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Re: 1991 Mustang GT w/ R12 - need help

Post by tbirdtbird »

Just for the record, most of us would lean the other way...remans tend to not to hold up well, and few us would buy anything from 4 squeezin's
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fastsvo
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Re: 1991 Mustang GT w/ R12 - need help

Post by fastsvo »

tbirdtbird wrote: Fri Sep 02, 2022 12:32 pm Just for the record, most of us would lean the other way...remans tend to not to hold up well, and few us would buy anything from 4 squeezin's
That bad huh! Ok, good to know!
tbirdtbird
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Re: 1991 Mustang GT w/ R12 - need help

Post by tbirdtbird »

At least get a price from Tim, can't hurt, and you'll be surprised!
When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com
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