A/C troubleshooting help please

[Joe_Cool]

Last June I drove from Albuquerque to Houston. The A/C was nice and cold the whole trip. On the way back, it started going intermittently warm and back to cold, and then a few hours later it started blowing only hot air.

When I adjust the temp controls on a cold day I can make it go from hot to cold and back at will, so it's not the blend door actuator. I'm certain it's not a freon leak, because I drained it completely and refilled it, and it has held the pressure.

What could be causing this? I need to get this fixed now that it's starting to get warm outside again.

 

[rubydist]

Several likely possibilities (in order of likelihood of being the problem, imho):
1. a/c clutch doesn't engage properly. This often manifests itself with the a/c working ok when the engine is cold, but not when the engine is hot and eventually not engaging at all. Check to see that the clutch is engaging when the a/c is commanded. If not, *carefully* rap on the a/c clutch with a broomstick. If this causes it to engage, then you need to search for and perform the "shim removal" trick.
2. bad pressure switch on the a/c line. Jumper that switch to see if that causes the a/c clutch to engage.
3. eatc not working properly. It is possible that the eatc is not commanding the a/c to come on when it should. If the a/c clutch is not engaging when you think it should be, disconnect the connector at the a/c clutch and check for voltage there.
4. interior temp sensor bad. It is possible that the interior temperature sensor is not detecting that it is too hot for you in the car.

Hope that helps!

 

[projectSHO89]

Good list above.

Check #1 first. You probably have a worn clutch.

 

[Joe_Cool]

The amount of knowledge here is mind blowing. Thanks for the tips.

 

[kumba]

OR... compressor took a crap.

I'd see if you can grab the hub of the AC pulley (WHEN THE CAR IS OFF! and been sitting for 10+ mins) and see if it spins over with consistent force and is not binding up or extremely hard to move. It's possible the compressor locked up and took the clutch with it. I'd probably check that somewhere around the broom-handle step in the above list.

I have a long love/hate relationship with Ford AC compressors. At least the SHO doesn't use that marvelous POS FS10 thing that Ford spewed forth on damn near everything else.

 

[Joe_Cool]

Well, it's not certain yet, but it seems to be the compressor.

Is the compressor interchangeable between 93 and 94? Or do I need to buy a new one?

 

[projectSHO89]

They are interchangeable provided you have the correct pulley.

 

[SHO SPD]

Sounds like you do in fact have a leak, I would check that first. Could be a leak so small it slowly goes out when operated at full pressure.

 

[Joe_Cool]

Sounds like you do in fact have a leak, I would check that first. Could be a leak so small it slowly goes out when operated at full pressure.

I'm going to have it tested for leaks, but I drained the system a week after it stopped blowing cold air, and it was (or at least strongly resembled) fully pressurized. So I don't suspect that as the cause.

 

[SHO SPD]

Its possible for it to still have pressure but not enough for the system to turn on. I have a small leak in mine so the A/C lasts about 2 months then slowly goes in and out and stops. But there is still about a pound of refrigerant still in the system, its just not enough pressure for the system to operate. But it is worth looking into.

Maybe grap a couple cans of the r134a cans from autozone or something and add that to see if it will kick back on.

 

[Joe_Cool]

Its possible for it to still have pressure but not enough for the system to turn on. I have a small leak in mine so the A/C lasts about 2 months then slowly goes in and out and stops. But there is still about a pound of refrigerant still in the system, its just not enough pressure for the system to operate. But it is worth looking into.

Maybe grap a couple cans of the r134a cans from autozone or something and add that to see if it will kick back on.

I tried that. It didn't work.

And it wasn't slow, it was over the space of a couple hours while driving.

 

[bobreimer]

First, find someone who is an actual A/C technician. Most service places start swapping parts until it works.

I had your problem. I found one mechanic in town who was a trained A/C technician. He tested it the system and in about one minute told me it was the clutch air gap. He reset the gap and it worked fine.

 

[Joe_Cool]

Update:

I finally got under the hood to check this out. I can turn the compressor manually, but the clutch definitely does not engage. I was poking at it with a broom stick, and found that I can move the front plate maybe a total of 3/4" side to side. I'm assuming that's not good.

Granted that I haven't taken anything apart yet, does this sound like a simple repair, or getting a new compressor?

 

[Joe_Cool]

Also, is there a step-by-step someplace for removing and replacing the compressor?