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Discussion Starter · #1 ·
I have a 1977 Ford LTD with a 351 Windsor that I've driven for about ten years. I've decided that I want to start using the AC in the vehicle, and I want to use the original R12 refrigerant. I know almost nothing about the condition or the history of the system. The following is about all the information I have:
  • The belt that drives the compressor was already removed from the car when I purchased it.
  • Everything looks to be intact other than one damaged electrical wire running to the compressor.
  • There is no sticker on the system that I can see that says it was converted to R134a.
I'm aware that certification is required to purchase R12. This is not a problem for me; looks like I can get certified with a test online for very cheap. But before I go full bore into tearing down this system, I wanted to simply patch the bad wire, put a new belt on, and run it to see what happens. Will anything be damaged by running what is probably an empty system for a couple minutes?
 

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I'd try turning the compressor first
If it won't turn it's most likely locked up
empty system will spread debris to the rest of the vital parts
If not already done so
 

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Welcome to the FFO!

Depending on the compressor, running without referigerant causes damage because the oil for lubrication is in the compressor

Getting R12 has some hurdles, but you have other things.
Can you spin the compressor?

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The first step would be to pull a vacuum. If it holds at least you know you have a tight system.
If it does not hold then fix the leaks.

Given the brief data you have posted
I would flush the system and then plan on compressor replacement and what ever metering the system uses.

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converted system will have adapters on the charge ports. with engine off, try turning the clutch hub. if it is free, jumper the clutch wire to battery for a second and see if the clutch engages. if so , start the car and jumper again. if compressor turns, shut down engine and do the vacuum thing.
 

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Discussion Starter · #8 ·
I attempted to turn the compressor by hand, but I'm not sure I'm trying to turn the correct part. The pulley where the belt attaches moves freely without any problems, but I'm assuming there's another part that should rotate. There's a rubber disc (for lack of a better word) on the front of the compressor. This doesn't seem to move, but I also don't want to apply a lot of force and damage it. There is a skinny metal disc behind this that I tried to turn. It wiggled slightly, but did not rotate. Though it is hard to get a grip on it given how skinny it is.

Below are two pictures of the compressor. The first is just a photo (which also shows the disconnected wire). The second is the same photo with parts highlighted. The green pulley rotates freely. The red disc is the part that wiggles.



I was given another Ford compressor from this era by a mechanic for free. He said that it was operational. It's in a cabinet in my garage, and when I tried to move components on it by hand, I got similar results.

I also looked at the fittings on my car, and they do seem to be R12 fittings, suggesting the car has not been converted. I took the cap off the fitting that was higher and closer to the firewall and gave it a very quick light rap with my finger. I heard some gas escape, which suggests there is at least some pressure in the system still.

I would prefer to use R12 over R134a. I found a number of buying options on eBay and don't mind the higher cost. I like to keep things original where possible, plus I always see mixed opinions on R134a conversions (I'm guessing the different opinions are based on the climate where the system is being used). Peak summer temperatures here are close to 100°F with 100% humidity, and I'm the type of person who doesn't like to go outside once temperatures are above 65° (I'm a big fan of winter). So I want to maximize every bit of coolness I can squeeze out of my AC.
 

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The "rubber" piece as you called it is attached to the crankshaft of the compressor. It should turn. It may have dome resistance. Turning it by hand will not damage it. If it is rock solid the compressor is locked up internally. Almost not worth rebuilding.

That is a A6 compressor. It will cool a small house.
Was made in very large numbers.
The Ford version is a little different than other applications

The R12 v R135 suggestion above has merit. (A lot of merit) Especially with the cooling ability of that compressor. If it was a different compressor that you needed to squeeze cooling out of sure but not that one. The evaporator may be the limiting factor. But for the 70s the company stepped up to much larger condensers and evaporators than were designed in the 1960s. In the 60s it was a bonus IF AC was even available. In the late 70s AC almost became standard. However the oil is not compatible between the two systems. Flushing is mandatory if you are making the change.

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A historical piece on the A6
Frigidaire A-6 Air-Conditioning Compressor | Hemmings

And you need to find out why the system has been non-functional for a decade. Even if there is pressure in the system now, the pressures in the high side can get to a couple hundred PSI

Parts in your pic-
The green part is a clutch pully - it rides on a bearing that can be wore out.
The red is the clutch - electrically operated.

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Discussion Starter · #11 ·
Just went out and tried to manually turn both compressors again, this time with a bit more force.

The one in my garage did put up a bit of a fight at first, but I was ultimately able to get it to spin with only mild resistance. The belt-driven clutch pulley on that one is a bit stiff, though. Might need new bearings?

As far as the one in the car, the crankshaft seems pretty well frozen. I question if it's only frozen because hasn't moved in 10+ years, and would a momentary kickstart from the motor itself be enough force to break it loose and get it spinning again? But if I do that, then we're back to the potential issue of spreading debris throughout the system.

I'm assuming there's no way to swap the compressors without having to depressurize the system.

As far as why the system has been non-functional for at least a decade, that I'm not sure. That's why I'm trying to figure out the best way to start tackling the project while keeping the car as original as is possible/practical. Given my lack of experience with AC systems, I wonder if it might be wise for me to have the system inspected by a professional before I start going off half-cocked. I have no aversion to doing the work, but I'd hate to do more damage than good simply because I didn't know what I was doing.

And you weren't kidding about cooling a small house with that thing! Those outputs in that article you linked are huge. I'm quite impressed.
 

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Unless you have some experience, now maybe a good time to farm this job out.

Unlike older compressors, there is no isolation for this one OR for any newer ones.
And isolation is NOT what is desired at this point.

For an unknown system that has been down for a decade with a questionable compressor ..
Remove all of the charge if there is one
Remove the compressor*
Remove the suction throttling valve*
FLUSH what is left.
Once that is done I would strongly replace with new/rebuilt/remanufactured compressor and valve. Otherwise a system failure is possible with little use. And most good shops are not going to just partially do this kind of work. It leaves them exposed to a repeat repair on an old system that has been dormant.

You the same job and save yourself labor. However you will need -
An AC gauge set
A vacuum pump
A flush kit
Basic hand tools to remove the pump and valve
Gas of your choice. If you go to R134a you will need fitting adapter

Lastly R134a is being phased out. It is available for now and it will go away soon.

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*These parts either generate debris or trap debris.
 

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Discussion Starter · #13 ·
I think I'll get a quote from a shop before I proceed. If it's cheap enough, I might let them handle this job. I'd prefer to learn how to do this myself, but this is my primary car which I plan on continuing to drive for many more decades, so it's probably not the best vehicle to use as a learning tool on such an expensive system. I have other vehicles of a similar vintage with bad AC that I don't drive every single day in the summer, so they might serve as better vehicles to practice on. If I botch the job on those, they were vehicles I never expected to have AC anyway.

Looking at the prices of the equipment you mention, they're not too bad. I suspect they'd be significantly cheaper than getting the work done at a shop. I'm fearing a multi-thousand-dollar quote if I don't do the work myself...

R134a being phased out is another reason I'm hesitant to convert this vehicle from R12. Given I plan on driving this car for a very very long time, it's hard to justify converting from one obsolete refrigerant to another. Since I started this thread a few hours ago, I have gone online and gotten my 609 certification through an EPA-approved affiliate, so I can now legal acquire and work with R12 if I choose to do so. There are a number of sellers on eBay with "virgin" R12 that was canned before it was phased out, and the prices are not unreasonable on some of them. I also found a number of people selling "R12a" for cheap, which can be used in R12 systems. But doing a small bit of research on that, it seems to be a highly flammable substitute, so that looks like something I'll avoid.
 

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no suction throtlling valve on ford. it will have a txv(thermostatic expansion valve). any ac shop will have a recovery system to drain your left over r12. the equipment cleans and stores the refridgerant for future use. do not let it out to the atmosphere. ozone hole yyou know?
 

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no suction throtlling valve on ford. it will have a txv(thermostatic expansion valve). any ac shop will have a recovery system to drain your left over r12. the equipment cleans and stores the refridgerant for future use. do not let it out to the atmosphere. ozone hole yyou know?
Hello redrag,

Actually Ford did use suction throttling valves and the original poster should have one on his car. A6's were typically non-cycling systems. So his suction throttling valve has the absolute pressure chamber calibrated to hold around 35 degrees in the evaporator with R12 if it's the original. They should be adjustable (might be able to adjust it to R134a if he wanted to), but you have to remove it to adjust it and there goes your refrigerant.

I know they sell those cheap aftermarket kits that replace the POA-STV's with a tacky cycling setup. Personally I like the non-cycling systems. My old Caprice Classic convertible has a very similar A/C to the '77 LTD.

To the original poster:

If you replace the A6 make sure it's the exact same one. There are two different displacements in the same physical package. There was a smaller displacement used for Corvettes and pretty much everything else had the 12.6 (I think, been a while) cubic inch version. Also the back of the A6 can be different. Some A6's have a port for a high pressure switch cutout and that obviously is connected to the high side port, then there is the A6 with the superheat switch and that port is connected to low side, so check that as well.

If the hoses are original, do yourself a big favour and have them replaced they are old and rotted by now and if you do get the system to run, it'll probably will pop the high pressure hoses for sure. R12 is to expensive to waste. If you do convert it to R134a, that stuff is very cheap right now and I'd stock up, but then if a hose pops it's not as expensive. There's nothing wrong with R134a. You should have new hoses made anyway and they will be the barrier hose for R134a. The compressor and condenser are HUGE on your LTD as it is on my old Chevrolet, it will have no problems cooling on R134a. You will not notice. I've converted a '66 full size Ford with a much smaller A/C system and it runs 37 degrees out of the vents at idle on a 90+ degree sunny day, with the windows down and blower on high. Like I mentioned you won't even know it's R134a in your LTD.

A couple more things, just replace the Thermostatic Expansion Valve. If the system has been non-op for long periods especially with no refrigerant that pintle is probably stuck and it will not meter liquid refrigerant properly. Now if the compressor is locked it probably shed metal in the entire system and that means burnt mineral oil and metal in the condenser and in the evaporator. They will need to be flushed really well.

They are reproducing the A6 again, dunno how the quality is, but they are expensive and if you splurge for a new one the last thing you want is to ruin it with bad oil and debris hiding in the system.

As always replace the receiver dryer, it has desiccant that is probably old and dead and maybe saturated by now. As always make sure you use the proper oil for R12 (mineral oil), DO NOT USE PAG, you can use Ester if you really want to. Be sure to add the proper amount of oil to compressor and lines before adding refrigerant. The A6 has a sump, with a drain plug (obviously under pressure when charged) and it also has its own oil pump which I think it kind of neat.

Good luck.

Cheers
 

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Discussion Starter · #16 ·
Coming back to give a few updated bits of info on this. Sorry if this a bit rambley. (Also, thank you to the people who posted after my last message; don't think I got notified of your replies.)

For starters, I found a copy of the ad from ten years ago when I bought this car. The ad said the AC compressor was three-years-old (at that time) but the AC wasn't blowing cold. The ad recommended that the system be converted to R-134a and recharged (suggesting the only problem was a small leak). So I'm thinking the compressor locked up from sitting idle for the last decade (since it's never even had a belt on it since I got the car).

That bit of backstory aside, I had to call quite a few shops before I found one that would work on the car, but I just finished up there today. The mechanic was very nice and let me watch him work so I could learn more about tackling AC repairs myself in the future. I told him what I knew, brought in my extra compressor and some R12 cans (since he had none on hand), and let him have at it.

When he started, there was no refrigerant left in the system but he was able to pull a good vacuum. He pointed out that oil had leaked from the back of the old compressor and based on how insignificant the leak seemed to be, it was hopefully just from bad seals on the two line ports there. My extra compressor had a semi-stiff pulley, so he took the good pulley off the frozen compressor, swapped those, put new seals on the back, and put the replacement compressor in. While the compressor was removed, he looked inside the lines for debris and saw none, so he said he felt no need to replace any other parts. He added some oil, which he said had some leak detection dye in it, and then started adding the R12. This is where we ran into a slight problem. I brought four 14oz cans, but two of them leaked while attempting to add. One of them was really bad and I'm willing to bet none of it actually made it into the system. After he added what I had, he said the high pressure line had the pressure he wanted, but the low pressure line was a little lower than he'd like to see. He said if it were his car, he'd probably buy a bit more R12 to add. The temperature is operably cold, but certainly nothing to write home about. He said run it and if the performance drops, bring it back in because there is a leak somewhere other than the seals he replaced (which he'll hopefully be able to find due to the dye in the oil).

I'm a little leery that he didn't replace any other parts based on what people have said here, but I guess at this point I'm just playing a waiting game since the job is already done and the system seems to be working. I'm not sure if I want to add a bit more R12 like he suggested right away, or wait and see if the system leaks to minimize wasted refrigerant. I think I'm going to buy a thermometer to monitor the temperature at the vents instead of just trying to go off how it feels to my hand (tried to hold a disconnected wall thermostat in front of a vent and got 51°, but I'm not sure I trust that number). Out of curiosity, does anyone here know what the capacity of the system in my car is?
 

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Hello,

So something is still amiss if your A/C on recirc (max) at even idle doesn't feel cold - cold. The vents closest to the evaporator core should be around 35-40 degrees depending on interior heat load.

You mentioned the mechanic said the high side was ok, but the low side pressure was too low? Do you have the readings? For the low side was he measuring evaporator pressure or suction line pressure? Not sure if there is a schrader port on the low side hose. If it was evaporator pressure (before the STV) and high side was in range for the heat load and outside temperature and if the sight glass was clear then I'd say the expansion valve is stuck or just plain inoperative and not letting in enough refrigerant. Those expansion valves are only around 20 dollars (Rock Auto) and it would have made good sense to install a new one since you had the system open. Also if the receiver drier wasn't replaced, it could have been saturated with moisture and you have moisture contamination as well. A stuck expansion valve can also flood the compressor with liquid refrigerant under low heat load and ruin the compressor.

Did the mechanic measure the evaporator superheat? It would be interesting to see where it's at.

Also too for an unknown system that's empty and you're replacing the compressor, I would have not only replaced the expansion valve (cheap insurance) as well as the receiver drier, but also cracked the lines on the evaporator and condenser and blew them out and any oil in there.

Then in the factory service manual it should list the dry oil charge and total refrigerant needed. You add the oil volumetrically and the refrigerant gravimetrically and that takes any guess work out. The A6 has an oil drain plug and obviously old oil should be drained first.

I would advise not adding more refrigerant until you have more information. I am not sure of the exact refrigerant charge but I would imagine for that car with that system it's between 3-4 pounds. My '73 Chevrolet with a very similar system is 3.75 lbs of R12.

Cheers
 

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Ditto on the expansion valve not correctly working.
If the expansion valve is getting replaced, do replace the reciever dryer.

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Discussion Starter · #19 ·
Ugh, I'm kind of wishing I'd just bought an RRR machine and done the project myself. Having it done at the shop was cheaper (and I thought wiser), but now there's a lot of stuff I don't really know the answer to, and can't answer without buying equipment anyway.

I re-tested air temperature with a different thermometer that I could stick in the vent and got a similar reading. It was a tiny analog thermometer, but it looked like it floated between about 49 and 53° at the passenger vent positioned at the top-left of the glovebox. Temperature outside today was in the mid to high 80s, so nothing crazy.

Unfortunately, I'm not sure what the readings were on the high and low pressure lines. And yes, he said the high pressure line was good, but the low pressure line was lower than ideal. Is the sight glass what shows if there is moisture in the system? I'd think he would have checked that. If the receiver dryer was saturated, would it have shown moisture in the sight glass? I can't say I know what evaporator superheat is, so I'm not sure if he measured that. If it's not something that can be measured with the RRR machine, it's not a measurement he took.

The reason I brought up the capacity of the system is because I had enough cans to put in 3.5 lbs at most, but given that the rim of one can failed completely the moment the hose was on it and I suspect none of it actually made it into the system, I think I'm actually sitting at about 2.6 lbs. Assuming the system should have over 3 lbs, being that low seemed like both a plausible explanation for the less than perfect performance and a good reason for him to recommend I add another can at home. But that may have just been wishful thinking.
 
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