How to: - 1st Gen. (R-12) AC REPAIR DIARY | Ford Explorer Forums - Serious Explorations

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How to: 1st Gen. (R-12) AC REPAIR DIARY

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EF Tranny Guru
Moderator Emeritus
February 8, 2003
Reaction score
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
A couple years ago I completely rebuilt my 92 Explorer AC system and enjoyed nice cold air. This spring, well... no cold air. So what follows is the diagnosis and repair of that system. I offer this in hopes it may prove helpful to others. I admit I do have access to some things that not everyone does, but at least you can get the flavor....

Well let's start with the diagnosis. I had no cold air, at all. I started the engine and turned on the AC and opened the hood.... no clutch operation on the AC. Uh oh, not a good sign. Generally means lack of adequate charge to get the low pressure cutout switch to engage, and as you shall see, LOW means LOW!!!

First thing I did was to remove the low pressure port's on the accumulator on the passenger side...


Next, using a sophisticated tool, I checked to see if there was ANY refrigerant in the system (pressing down on the core in the schraeder valve)


NOPE. Nada, zip, zero. THAT translates into gross leak. But without a charge how to test? You CAN use a vacuum pump and see if it holds vacum, and then oil the joints but that's a poor way in my opinion and only operates at atmospheric pressure (approx 15 psi). Better is to add refrigerant..... but this is an R-12 sustem and that stuff is EXPENSIVE! Wait.... I just did a home AC for a friend and my gauge set has a couple OZ of R-22 trapped in it! What to do? Hook it up and let the R-22 pressurize the system!

[There is a guy who thinks R-22 is the best of all worlds for leak testing - for one thing it has higher pressures for temperatures, and he believes it makes it way past oil barriers. Plus it is cheap! Right or wrong that's where we are headed.]

I drag out the gauge set (one of my favorites for reasons I will explain) and hook it up.


Those couple ounces have pressurzed the system to about 80 psi! (point why a "pressure check doesn;t really tell you charge state in AC work) I was going to get my "sniffer" but could hear hissing.... it was a GROSS leak all right, and right at the manifold that connects the lines to the compressor. Problem identified.

I removed the bolt, and here's the manifold.... it was the innermost seal that was leaking.


There are two O-rings on the back of the compressor.... I removed the offending one, and here's a pic after I did..


Tool of choice ?


Made right here in the good ol' USA.... oh, wait.... nevermind.

Just hook the O-ring and pop 'er out...


(I had a strange desire for potstickers after I did this)

I replaced the older Nitrile O-rings with newer HNBR (green) ones lubed with NYLOG


lossely fit the manifold for this pic...


There is one bolt that holds this together. Long time members of these forums know I am a locktite freak.... I added a little blue to this bolt....


(ok it IS a crappy pic, try doing this while also taking the pic!) Anyway... here it is all back together...


WHOA you say, what is all this about green O-rings and NYLOG? Ok, let's digress, since it is all back together.

Let's talk O-ring material. In the "older days" it was butyl rubber... then came a big advance... nitrile.... lasted a long time. When 134 came in, the molecules were smaller and nitrile wasn't good enough, so they came up with HNBR... for the life of me I forgot what that stands for but will find it in one of my books and post it, for us let's just say GREEN is BEST! R-12 is ok with Nitrile, but 134 isn't. IN the AC field we are going GREEN! I have a box of Harbor Freight O-rings, and also a box of AC Green O-rings.... here is the offending O-ring:


Why did it fail? I have no clue. Here it is next to a HF nitrile O-ring, same size


and here next to a "greenie"


the HF would be ok for R-12, ONLY.. repeat, ONLY greenies work with 134!!!

So here a full set of each next to our bad boy...


You can buy green O-rings in a master set online for about $30 or by the ring at any AC repair shop.

NYLOG. great stuff. It is THE very best lubricant for O-rings and can prevent leaks.... trust me on this. It comes in 2 flavors.. one for R-12/22, lighter colored:


and a darker colored one for R-134


I recommend NYLOG highly. If you cannot get it, best 2nd, for BOTH R-12 and 134 ? mineral oil. Plain old mineral oil. Ok, we get that all settled ?

I had added a new accumulator 2 years ago. This one was "probably" fine but with no pressure in it I wanted to take this chance to add a new one. SO, $40 later I had an exact replacement. I'll clean the old one up, oven bake it and sell it for $10.


Let's walk through the steps to replace one. The R-22 charge was recovered, so the system was empty.... in my case. NOT YOURS ! MAKE SURE YOU DO NOT HAVE ANY CHARGE LEFT and wear eye protection. DOING THIS ON A CHARGED SYSTEM IS DANGEROUS AND COULD CAUSE THE LOSS OF VISION!!! Ok, warned enough? I am serious. BE CAREFUL ! PLEASE.

First order of business is to remove the low pressure cutout. In doing so I am gonna bust a myth. But to start, we removed the electrical connector by gently pulling it off (gently my ass, but be careful as you go)


and off


Next something to undo the switch... it screws on and is not on "tight" but more than finger tight - barely.... I got it started


then used my fingers


WAIT STOP!! THEY SAY... NO there is nothing to stop the refrigerant, "you will go blind!" (and I didn't go blind doing THAT either, thank you, though I shave my palms)


Well I'll be damned... there IS a schrader valve and a greenie. (myth #20887 BUSTED). You can take the low pressure valve off a fully charged system, safely.

Ok next up, the garter spring...

These are a unique thing... you need a special tool to release them...
The tool can be plastic... inexpensive, here is an autozone set, about $10


(also thinkin this thread cements my place in history as having my hands as being the most photographed on the net)

This has a protective guard to hold it all together, so we remove it first


and off


So you find the right size (black in my case) and slide it into the back of the fitting.... expanding the garter's the tool


"oh baby slide it IN" (stop that)


and voila, it pulls apart


there is also a flange nut to undo


and lastly a clamp down at the bottom


Ok once it is out, drain the oil from it...


Notice the color, it has dye in it, here is that dye


(the dye was no help in a long time slow leak, it gets carried by the oil..... so DYE is not as good as a sniffer, by far) anyway we add the same oil to the new accumulator, a little to each side


Word of wisdom here. People often get the wrong accumulators. They all come with new green O-rings, make sure your has them in it, if not get another one that does....


Let's recharge!

Now to the Q of why I love this gauge set so much (btw the high side is screwy I blew it out on the home AC job, it needs a new gauge)

Anyway here is the gauge set hooked up, notice anything?


4 yep, count em (four) hoses! One to the pump one to the supply and one to high and low... I can evacuate everything! Notice the hose size to the pump. I am told that at low vacuum size is important.... (thank gawd we do not live at low vacuum)


After a minute, I am nearly at 30 inches vacuum


I ran the pump for an hour.

Meanwhile I set up the charging refrigerant. R-12 is not available in cans anymore, so you have to buy a "jug" (about $800 these days). So how do you measure out the charge (in our case 28 oz?). You use a scale. Here is the jug, upside down (liquid dispensing) on the scale [Note I used 32 oz when I did this thread, the correct amount of R-12 should be 28 OZ, NOT 32 OZ I apologize for the error]


and I zero the scale


When everything is ready I open it up and let the vacuum suck in liquid refrigerant... it equalizes at almost a 3/4 charge


I turn the jug right side up, start the car and finish like that, charging as a gas...


the final charge


1/2 oz over.

The low side operating ? (remember the high side is broken)


Vent temps around 50 'ish at the curb in 90 degree weather, vents nearer 40 at highway.

Job done. Who's buyin the beer?

Thread officially open for comments etc

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Before you spend money on a new gauge, try swapping the charge hose (small yellow) for the red one ... it's not uncommon for the seals to deteriorate, restrict the hose and cause false readings ... also take the gauge off and check the inlet for gunk ...

I have the exact same charging maniford and ironically just today the high side hose went bad and although it seemed to read the pressure correctly when you 'reversed' the flow and tried to charge as a liquid, it would close up and the refrigerant just couldn't get in (at least not very fast) ... that little built in sight glass (nice feature) is what clued me in that something was wrong (besides my scale barely moving) ... swapped a hose from by backup (company supplied) set and all was well .... it would have taken all day to charge 12.3 lbs of R22 through that restricted hose ...

Now if I can just convince the service manager that changing the hoses every spring would save money in the long run (you would think people who push preventative maintainence contracts would know better themselves) ... waste a half an hour labor jacking around with bad hoses and you bought a new set anyway ... so I'll just do the usual, get a new set next time I'm at the wholesaler and argue with him about it later ...

I should also mention that refrigerant can toast your lungs as easy as your eyes (easier if in an enclosed location) ... back in the early 80's my Dad was working in a small room on a system that was grossly overcharged by someone else (Condenser coil was built in wall) and before he could even get his charging manifold on it, a joint on the liquid line blew out (The hack used 95/5 plumbing solder) and it damn near killed him, 1st by toasting all the little 'hairs' in his lungs and again a couple of weeks later by the heart attack brought on by the physical stress on his system ...

Thanks, I'll check that!

Sorry about your Dad!

(and for those considering ever soldering an AC system you ONLY use silver solder! And special Silver solder at that!)

I once made my own vacuum pump out of an old window style A/C. I removed the 110 volt compressor, and mounted it inside of a wooden crate, with a switch. I connected a refrigerant hose onto one of the ports for this contraption to act as a vacuum pump. I saved some money instead of having to buy an electric vacuum pump. I've previously used a manual hand pump which took a really long time to pump out an entire system before I made this. These compressors were really heavy compared to the new ones they now sell.

This is an awesome write up, thanks for posting it!

I have an old system that has been at zero from before I owned it.

Im thinking about replacing the hoses and going from there, is there anything that is smart to replace before doing a vac and pressure test on it?

uh oh

So out of curiousity if I didn't know my 92 explorer used r12 and I filled her up with 134a did I just screw my entire system up?