A/C compressor

Recently I was using my A/C. During this time, the compressor would drag the engine down by a couple hundred RPM when it cycled. After a while, it caused the car to stall. I unplugged the compressor and checked it again after the trip. When I plugged it in with the car idling, it dragged the idle down until the car shutdown, a time period of about 3 seconds.

The A/C was adequately cold.

It has cycled since being refilled last year, it was not filled to full pressure.

I am curious to know if the compressor is beginning to lock up, or if there can be another problem causing the compressor to drag.

New compressors are between 250 to 300 dollars, and if my compressor is siezed it will likely require replacement of all associated components. Therefore this is unlikely to happen. I am simply looking to at least partially restore operation.

I disected my old compressor 2 years ago and really looked it over last wknd to clear some room from my work table. When mine went, it was completely locked up. There are 5 double-ended pistons (for a total of 10 cylinders) that are driven back and forth by an angled swash plate between them. Each piston has a single teflon ring/band about 1/8" wide which seals it to the cylinder. That's 10 bands total. What happens is the bands break and get pushed up into the reed plate which will cause a loss of pressure and eventually when enough of them go, it will sieze up. In my case, 5 of the 10 were completely gone.
My guess is that maybe you've lost one or more bands, but not enough to cause to to lock up. If you don't run it, you might get lucky and the band pieces would still be stuck in the reed plates meaning that your condenser and liquid line/Otube may have been spared. Its worth it, IMO to see if you can get a used one.. Any Ford FS-10 will do. When you pull the old one, dissassemble it and inspect it to see just where the pieces went. Consider flushing the condenser and HPline/manifold and replacing the liquid line ($30) anyway. You can take a chance on the accumulator but only if you disconnect it and cap off the ends quickly. Better to replace it if its old, but its your call. If you have the original R12 (freon), call around and see if a shop will reclaim it and give you some $ credit on a recharge. Here's the hitch.. they'll have to evacuate it first before you can do any work on it, so it'd be a shop credit.
That's my $.02. Hope it helps.

Here's some pics of what I described.

TbirdSCFan; its very helpful.. thankyou!

Now I must clarify a few things: first, the liquid or O-tube is the orifice in which the freon changes from a liquid to a gas? And where is it located? Next, I was hoping you'd say the compressor was used for multiple cars, and it sounds like it is. What cars can I find the FS-10 on? And if I acquire from a junkyard or similar, what if anything can I do to help confirm its condition? Another thing, where exactly is the accumulator and what should I cap the lines with to seal well?

Thanks again for your help. A friend has access to more freon and the ability to flush it.

Digitalchaos said:

TbirdSCFan; its very helpful.. thankyou!

Now I must clarify a few things: first, the liquid or O-tube is the orifice in which the freon changes from a liquid to a gas? And where is it located? Next, I was hoping you'd say the compressor was used for multiple cars, and it sounds like it is. What cars can I find the FS-10 on? And if I acquire from a junkyard or similar, what if anything can I do to help confirm its condition? Another thing, where exactly is the accumulator and what should I cap the lines with to seal well?

Thanks again for your help. A friend has access to more freon and the ability to flush it.

Click to expand...

The liquid line is the bottom line from the condenser going to the fitting in the firewall. The liquid line has the Otube built into it. They slide it in, crim the line to hold it, and the bend it into a square U shape. All this means is that you have to replace the whole line, but it only runs about $30 so its not a big hit. You can't replace the Otube without cutting the line.
The reason the want you to replace it is small particles can build up on the screen and possibly clog it. To me though, if the old compressor didn't belch out any of the bands, I'd try to flush it from the large end to the small end with brake cleaner. Note, if when you do this, a large amount of black crud comes out, it may be best to flush the condenser and the high pressure line/manifold as well.
As far as the accumulator, its the black or silver canister just in front of the firewall. Its job is to catch and hold water in the system. Usually, you replace them if you ever open the system up as air gets in, they get saturated and can become ineffective; its a judgement call. To cap it off, you can use saranwrap and rubber bands. With a used compressor, I'd probably reuse the old accum as you don't know how long its going to hold up... No scratch that.. if anything an old compressor probably could use more protection, so its safer to use a new accum. Moisture is what kills compressors to begin with, so the dryer the insides, the better.

I think the Ford FS-10 (or Fx-15s) are quite common from 1990-95. Probably best to take a pic of yours to see that the manifold (brass block with the steel lines) bolts up the same. It is possible to unbolt and twist the body of the compressor 180 degrees if that gets things lined up.

To check a used compressor, if you can turn the shaft, not the pulley itself, with out a lot of force, then it should be fine. It will take a bit of extra force to get it started turning, but then it should turn smoothly. If I had to put a number to it, Id say it takes about 10 ft-lbs of torque to keep it moving. Give it at least 2-3 full turns.

When you refill it, you'll need to add about 6-8 oz of mineral oil and install new Orings lubed with mineral oil also. Then when you go to refill it, hook up a vaccuum pump to both ports (if you can) for 30-45 minutes to suck out all the air and moisture and then charge it up. Be sure to keep any air out. To do this right, you need a set of gauges and you need to purge the air out of the hoses; there's a bit of a trick to it, so post back if your friend isn't familiar with how to.

I'm attaching some pics of the various parts. Hope this helps.