A/C dilemma

[SilSho95]

My A/C on my 95atx was not working, so I assumed that I had a leak somewhere and left it at that. One day last week for the **** of it I bought a gauge to check the pressure in my system. I hook up the gauge to the low side valve near the firewall, and it reads 65 psi so that rules out leak. So I start searching through the threads and get a couple of ideas. First with the engine running and the A/C on I tried to tap on the clutch hub with a wrench and it stuck to it like it was a magnet. I assume that means the coil works, Second I removed the clutch hub and checked the clutch gap there were 2 washers one thick one thin I removed the thin one because the thick one measured .35 I put the hub back on. After I put the clutch hub back on with the a/c on the clutch starts engaging for three seconds and releases it just keeps doing this over and over again. I put the gauge back on while it's doing this and the pressure drops from 65 psi down between 25-35 psi before it shoots back up because the clutch dis engages. I head back to the auto parts store and buy a can of r-134a, I assumed that maybe there wasn't a proper charge. After adding the refrigerant it still does the same thing, so I decide to replace the clutch hub. I go to Bison Ford here in town(to my surprise they had the part in stock motorcraft for $47). I replaced the clutch hub and still no change. So now I'm stuck I'm not sure what else to do and I don't want to keep dropping money on this. Could it be the low side cycling switch? Is that on top of the accumulator? How hard is that to replace? BTW I really appreciate this forum from all the searching through threads the guy at the auto parts store said it sounds like I've been working on a/c systems for a long time because the way I talked about it. This is the first time I've worked on an a/c system(I told him "no I've just done alot of research").

 

[Rob94]

It's possible that you are still low on refrigerant, or the pressure switch could be bad. Check your pressure with the engine running and AC on again. If it drops down to 25, then shoots back up, you are still low.

 

[projectSHO89]

The switch is fine and is doing its job. You're still a bit low on the charge.

Steve

 

[Mr Anonymous]

You don't set the gap by measuring the shims, you set the gap my measuring the gap -- with the hub installed -- with a set of feeler gauges.

I'd suggest trying a new pressure cycling switch (on top of the accumulator).

 

[rangerj]

If you have to add refrigerant, you have a leak. Look for signs of a leak at the A/C connections. The signs are generally black oily dirt around the connection, or on the condenser, or behind the clutch coil.

As stated above the clutch gap is the distance between the two clutch surfaces, that is the hub surface and the pulley surface. The gap should be approxamately between .025 and .035 inch.

When the gap is too large the clutch will also "cycle", but your problem would seem to be a lack of pressure due to an insufficient charge (based upon the pressure readings given). If you are not able to maintain a charge, then the leak needs to be addressed. rangerj

 

[SilSho95]

I put the gauge back on, first with the engine cold(sitting overnight)and the a/c off it read 65 psi, second when the engine reached normal operating temp and the a/c off it read 90 psi . BTW before I messed with the clutch hub it would not engage at all, after I removed one of the washers is when it started engaging on and off. Could it be the cycling switch?

 

[SHO_Driver]

Short the cycling switch and see if it blows cold.

 

[shojuan]

I put the gauge back on, first with the engine cold(sitting overnight)and the a/c off it read 65 psi, second when the engine reached normal operating temp and the a/c off it read 90 psi .

That's normal. In both cases the high side and low side have equalized. This means the low side reads higher pressure than it will during operation and the high side will read lower pressure than during operation. And it just read 90 psi because the ambient temperature in the engine compartment was higher after the engine warmed up. If your clutch would keep the compressor engaged then you would see the low side pressure drop during AC operation and more or less stay in roughly the same spot.

You might need a new switch because your AC was short cycling at pressures higher than typical. 25-35 psi during positive AC operation should not trigger short cycling. If it dropped down to 15-20 psi then sure, the switch is behaving normally and you would need to add refrigerant because you had a low charge as indicated by the 15-20 psi pressure. But 25-35, that would suggest you have an adequate charge.

So switch could be bad. Or you could have a flakey field coil. Or both.

 

[SilSho95]

I'm wondering if this is a clue to what's wrong with my a/c. The temperature outside is starting to drop around here at night,so yesterday I was driving and I turned the heat on full blast. The clutch starting engaging on and off the way I described it earlier in the thread. Is it supposed to engage with the heat on? I haven't had time or money to replace the cycling switch yet.