Question More AC Questions

[femurphy77]

I've searched the various forums and have come up with a few general ideas but am hoping somebody with BTDT experience can chime in. While driving with the AC on it blows great for awhile then the compressor disengages, the air warms up and stays this way for varying amounts of time. After a little while the compressor kicks back in and we are blowing cold air again. Maybe coincidentally it seems to do it more after I drop the blower speed in the truck. I've checked the charge with one of those gauges that comes on the top of some cans of freon and it is in the high end of the good range, checked the electrical connection at the compressor and the pressure switch but nothing has cleared up the problem. Is there a spec for the clutch gap? Clutch coil resistance? Or any other areas that I have failed to check? We are doing an Indy to Cleveland TN trip next month and AC is not optional, it's gotta work! Help!!!!

 

[keanoknick]

Fill in your signature with your truck details, it will help us to know what you're driving so we can better help.

I've had a similar problem with my truck, although I don't think it's the clutch or anything to do with the compressor, I believe it to be a vaccuum problem, that's not allowing the "flapper" valve to direct the air over the condenser coils, all of the time, then vacuum builds back up and it works again.

Hopefully someone that is more educated in AC systems than myself, will chime in shortly.

 

[95_stroker]

Sounds to me like the pressure switch is doing its job and is cutting out on a high discharge pressure. Have you hung a set of gauges on the system yet?

 

[femurphy77]

Nope, no real gauges yet. That's the next step. That was my suspicion but not knowing AC systems very well was hoping it was something I could handle in the driveway. If it's a high discharge pressure situation what are we looking at; orifice valve blockage? It's a 2000 SDD, 4dr, 4wd, AT.

 

[Potentialbuyer]

It sounds like the evaporator is freezing up because the compressor is not cycling correctly. You will need a set of guages to proove this. If the orifice was plugged, you probably wouldn't get any cold air at all. A way you might be able to check for a freezing evaporator is to run the truck at a fast idle with the air on and look at both hoses that go into the evaporator. When the compressor engages, the hoses will sweat but if the evaporator starts to freeze, the hoses will build frost on them. The compressor should disengage before the hoses frost up. You could have too much refrigerant in the system too. If you have access to a Ford service manual, they give cycle times (compressor on and off times as well as total cycle time) that give you diagnostic information about the refrigerant system. You can get a better idea of what is going on before you put a set of gages on it.

 

[JLDickmon]

Nope, no real gauges yet. That's the next step. That was my suspicion but not knowing AC systems very well was hoping it was something I could handle in the driveway. If it's a high discharge pressure situation what are we looking at; orifice valve blockage? It's a 2000 SDD, 4dr, 4wd, AT.

there's a lot of "could be's" but I need to know what kind of gauge readings you're getting at about 2,200rpm

if it's bone-frostin' cold at idle, I doubt a system blockage.
Plugged orfice tubes tend not to "cure" themselves, nor "clog" only at high compressor speeds (and are usually a sign of impending doom; i.e., compressor failure).

Actually, my GUESS (I'm not standing there looking at it, and don't have gauge readings) would be an airflow or other problem with the condensor not giving up heat. Make sure all your shrouds & ducts are in place, and not busted all to chit... might even check the condensor fins for damage and make sure the mice disn't build a nest between condensor & the intercooler...

no one painted the condensor to make it look better, did they?

oh, and stick a thermometer in the center vent and tell me what temp it blows when it's "working" and what it warms up to when it's "not working"

most everything uses a variable displacement compressor nowadays, that's why I need to know pretty much what's happening & what's been done to it.

If you can tell me what the pressures are and whether or not the needles are steady or if the jiggle like a tweeker on meth...

 

[JLDickmon]

Is there a spec for the clutch gap? Clutch coil resistance? Or any other areas that I have failed to check? We are doing an Indy to Cleveland TN trip next month and AC is not optional, it's gotta work! Help!!!!

yes, there is.
(to both questions)
can't remember what they are off the top of my head...

 

[Tbar]

When it stops working........get out and give the front of the clutch a thump with a screw driver.

If it reengages you may need to remove a shim to tighten the gap.


Tbar

 

[Potentialbuyer]

The Ford service manual says that there are seven possibilities for erratic compressor operation. 1. Fuse 2. Wiring 3. Cycling switch 4. System pressures 5. A/C pressure cutoff switch 6. A/C control 7. A/C function switch. The A/C clutch air gap is .014"-.030". I couldn't find a spec for the clutch coil. When the system stops working, check to see if you have 12V at the clutch coil. If not, go back to the cycling switch and see if you have power there. If you have 12V at the coil, chances are that the coil is bad or the gap is excessive.