Easy fix, AC cold in traffic again

[JOAT]

My AC has been getting to where sitting in traffic it would cycle off, then wouldn't come back on till I got moving. Pressures were normal when the compressor was running. I then found the compressor clutch wasn't engaging at low RPMs when the system had been on awhile. Checked the manual and found the clearance on the clutch should be .014-.033" and mine was .045! I took a washer/shim out from between the cluch hub and the compressor shaft which left me with about .012 clearance. It has operated flawlessly since.

 

[johndeerebones]

on the a/c note, see if you guys got any ideas. I also have a 4 cyl 5 speed 96 dakota. Charged up the a/c and it cools ok, other than it should do better. the low pressure switch kicks out he compressor at like 30 #s, so even just sitting idling the clutch cycles in and out at about 15 - 20 second intervals. I've jumped the switch and the pressures run fine, clutch stays engaged. Im sure if I left it jumped though it would freeze up the evaporator. The way the service ports plumb into the system I don't think the switch can see different pressures than my gauge is showing..? I even replaced the switch to see if it was kickin out at a higher pressure than it should or something, same results. Aren't low pressure switches typically supposed to change state somewhere around 10 and 15 #s?

 

[JOAT]

30 seems a bit high, tho it should still cool OK, just cycle more often. 15-20 second intervals is not bad, as long as it kicks back in fairly quick, so maybe the 30psi was intentional for that system. If you increase the charge a bit it will probably cycle less often too. Might kick off for excess high pressure in hot temps if you overcharge too much tho.

Mine is actually cycling of at 24-25psi, and I was thinking of replacing the switch even tho it cools really well. Manual for the Ford shows 15psi cutout pressure.

 

[lifted_up]

My AC has been getting to where sitting in traffic it would cycle off, then wouldn't come back on till I got moving. Pressures were normal when the compressor was running. I then found the compressor clutch wasn't engaging at low RPMs when the system had been on awhile. Checked the manual and found the clearance on the clutch should be .014-.033" and mine was .045! I took a washer/shim out from between the cluch hub and the compressor shaft which left me with about .012 clearance. It has operated flawlessly since. Brrrrrrr!

I had the same thing happening and did the same fix you mention and it's been going for two years since without a replacement.

 

[johndeerebones]

30 seems a bit high, tho it should still cool OK, just cycle more often. 15-20 second intervals is not bad, as long as it kicks back in fairly quick, so maybe the 30psi was intentional for that system. If you increase the charge a bit it will probably cycle less often too. Might kick off for excess high pressure in hot temps if you overcharge too much tho.

Mine is actually cycling of at 24-25psi, and I was thinking of replacing the switch even tho it cools really well. Manual for the Ford shows 15psi cutout pressure.

15 is along lines I was thinking, but I'm more used to expansion valve systems too, where the valve controls refrigerant flow, not the compressor on/off state.

I replaced the switch, so I'm sure it is designed that way.

The truck is superclean and straight, but the guy I bought it from, 2nd owner said they told him it had a different eng, both 4 cyl than new. Came stock with the 2.5 ohc engine, it now has the 2.5 cam in block engine like yj jeeps do, so maybe the r134a sticker is wrong, and it should have more, hadn't thought of that. I charged by weight, so I KNOW it has full charge by the sticker.

 

[johndeerebones]

15 is along lines I was thinking, but I'm more used to expansion valve systems too, where the valve controls refrigerant flow, not the compressor on/off state.

I replaced the switch, so I'm sure it is designed that way.

The truck is superclean and straight, but the guy I bought it from, 2nd owner said they told him it had a different eng, both 4 cyl than new. Came stock with the 2.5 ohc engine, it now has the 2.5 cam in block engine like yj jeeps do, so maybe the r134a sticker is wrong, and it should have more, hadn't thought of that. I charged by weight, so I KNOW it has full charge by the sticker.

I went to work this morning and got my gauges, some 134, and my infared temp gun, gonna maybe put a little more in it. When I first did it seemed cool enough, no temp gun though and I had the switch jumped to stop the cycling, but it wasn't hot out either. I hit the vents with the temp gun going down the road on the way home and it was only 65*, outside temp was only about 80, so definitely something wrong. I'm gonna feel along the lines for temp changes in the wrong places before I put some more in it, maybe I have a restriction somewhere in the lines other than the orifice tube.

 

[JOAT]

65* is pretty bad. If it's not low on refrigerant and pressures are normal I'd check for a plugged orifice, a ducting issue, or severe dirt buildup on the evaporator.

 

[johndeerebones]

65* is pretty bad. If it's not low on refrigerant and pressures are normal I'd check for a plugged orifice, a ducting issue, or severe dirt buildup on the evaporator.

WOW, same thing I went to yesterday. Its not low at all, pressures odly enough are reasonable, its just not cold, even after I jumped the low switch. Our recovery/recycle machine at work is at the repair shop for Robinair, so when it comes back I'm gonna get a new orifice tube and suck it down and flush it and check it out. I noticed almost immediately after I jumped the switch the line from the condensor to evaporator FROZE, not just frosted up, froze. The orifice tube I'm hoping is between the condensor outlet and that line, cause that is where the giant temp change is. Not long after that I'm sure the o tube became fully clogged, because it unfroze on its own, with the compressor still running so it had to almost stop refrigerant flow completely. Only thing I don't get, is the pressures never got out of whack. Oh yeah, pulled the bottom of the dash off and made sure the evaporator wasn't plugged up on the fins. The outlet tube of the evaporator is just air temp, not cool to the touch at all, so refrigerant isn't flowing like it should be...