Air conditioning - pressure switch bad? Reply #45 – July 10, 2010, 09:06:35 PM Guys, another summer is here and I'm finding weird issues with the system. At idle, I'm seeing 40psi low, 250psi high and at 2000 rpm's I get 30psi low, 325psi high. I adjusted the switch a half turn as it was turning off whenever it saw anything lower than 30psi. Why does it take 2-3 minutes before the compressor kicks on again when this would happen? Also, why after 15 minutes or so of driving (it can be stop and go or it can be highway), the compressor continues to run and gets near freezing while the cabin temperatures are still about 70?I get the following center-vent temperatures on a 90 degree day:Turn on AC and within 1 minute I'm down to 65 degreesTwo minutes and I'm at 55 degreesCompressor cycles on and off two to three times for the first 15 minutes.Half the time the AC stays around 52 degrees vent for the rest of my driveHalf the time the AC drops to a vent temperature of 38 degrees for the rest of the drive...this happened today and I kept it going - when I got to my destination, my hand was still cold about 5 minutes later.Why are my pressures so high now compared to last year when the system has not been touched and the temperatures are the same? 325psi high should be closer to 250, correct? Any lower pressure and my low pressure switch will begin to cycle unless I drop it down to cycle much lower...I use a Fluke 561 for my temperature readings with the contact probe intertwined with the vent. Quote Selected
Air conditioning - pressure switch bad? Reply #46 – July 12, 2010, 09:30:08 PM Now my low pressure switch is turning off at 45psi and screwing the adjuster either way apparently does nothing and I cannot hit a stop in either direction (should I?). It doesn't explain my earlier issue but this switch is bad, right? If I'm replacing it, I figure I may as well replace the orifice tube with a variable one? Is there one you guys would recommend or just pick up any ole' VOV from the parts store? Quote Selected
Air conditioning - pressure switch bad? Reply #47 – July 12, 2010, 11:19:51 PM Messed with it a bit more and it seems that once the cutout fires, a second later it tries to turn back on for a second before shutting off, and another second later it flicks on and then back off permanently. Messing with the screw, all the way turned in and back out, it'll work again but not if I hit around the cutout area again. At 70 degrees, it is dropping down to 28psi low/150psi high at idle, 19psi low/195psi high at 1500, and 17psi low/210psi high at 2000.I got down to 39 degree vent temperatures in the driveway with the doors closed for a couple minutes, 45 or so with the windows down. I'm sure it'd ice over terribly (and perhaps not oil well?) if I don't replace the low pressure switch.So yeah - appears bad low pressure switch to me. Should I try getting a Motorcraft piece from Ford or just grab one from the auto parts store? Still, what about the variable orifice tube? Is there a Motorcraft part number or just grab a parts store unit? Quote Selected
Air conditioning - pressure switch bad? Reply #48 – July 13, 2010, 08:45:09 AM You won't need to open the system to replace the switch, so I wouldn't mess with the orifice tube. As for the pressure switch, and decent aftermarket one should be fine. Just make sure it is an adjustable unit.Shiny Side Up!Bill Quote Selected
Air conditioning - pressure switch bad? Reply #49 – July 13, 2010, 10:56:26 AM Wait - I thought it was o-ringed and touched refrigerant directly? I know I'm still using an original unit from likely when the car was new so it's time but I don't want to pull it out and have the system purge all over my fingers...Autozone's (Chilton?) repair guides also say to evacuate the system? Quote Selected
Air conditioning - pressure switch bad? Reply #50 – July 13, 2010, 11:56:56 AM The cycle switch screws onto a schrader valve , you should not lose any measurable amount of refrigerant :D I just replaced the one in my fathers old F150 about a month ago Quote Selected
Air conditioning - pressure switch bad? Reply #51 – July 13, 2010, 12:18:40 PM Quote from: hypostang;328145The cycle switch screws onto a schrader valve , you should not lose any measurable amount of refrigerant :D I just replaced the one in my fathers old F150 about a month agoCorrect... it crews onto what is basically a charging port and should have a schrader valve.Shiny Side Up!Bill Quote Selected
Air conditioning - pressure switch bad? Reply #52 – July 13, 2010, 02:17:46 PM Thanks guys - that will do. So do my pressures from my previous post sound about right for a charged system? I know the less refrigerant there is, the better it will cool on hot days but it also means more cycling in the cooler months and with the defroster in the winter.I'm still not sure why I'm getting over 300psi on the high side on a slightly warmer day though. The condenser was only slightly warm (large 1997 Cobra unit) and the engine fan is new.Edit: In the driveway after a commute, my radiator was ambient temperature within a few minutes. Fan works very well, alongside the 3 core aluminum radiator. Quote Selected
Air conditioning - pressure switch bad? Reply #53 – July 14, 2010, 12:52:43 AM Replaced and the system works great now. Old oring ripped but I've got dozens of AC ones around. So after all this time, the title of this thread is finally coming to a close :p Quote Selected
Air conditioning - pressure switch bad? Reply #54 – July 14, 2010, 01:09:53 AM Good news , congrats Quote Selected
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