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View Full Version : a/c rpm dependency



paulkeith
07-08-2005, 02:21 PM
my a/c works perfectly at idle and anything under 1500 rpm. ice cold.

as soon as the rpm go up , like during acceleration or interstate driving, the cold air stops.

now from what i tried to figure out, this means i'm building up too much pressure, and its tripping the high pressure switch, right? i can feel the compressor start to engage and instantly shut off. but again, this is only at high rpm. not the 1000 that you're supposed to test the system at. low rpm it does not cycle excessively.

has anyone ever seen this? is there a clog? its at a shop and even they can't figure it out. only gave it to them because i figured they'd have it done fast, and i dont have the equipment to vacuum before charging, etc etc

did some searching on JU and only found posts about excessive cycling at the 1000rpm test point. doesn't relaly help me, plus the charge is good. nagca was down.

thanks
Paul

OverkillZJ
07-08-2005, 03:42 PM
I think you really need to get a manifold on that to check the pressure of the high and low sides, see what's really going on. Sounds like maybe the thing seperating high and low side might not be doing so properly, that's what caused me to replace my compressor a couple of years ago.

paulkeith
07-08-2005, 06:18 PM
i just spoke with the mechanic on the phone. this is a local guy, but has an excellent reputation around town for knowing A/C backwards and forwards. did some work on my dad's cars and they came out very well.


back to the point. he said that the charge was a little high (which is strange, because i haven't touched it other than checking pressure since i bought it with 93k miles in 1999...now at 175k miles). So he said he let some pressure out, and adjusted the high pressure switch. I didn't know this switch was adjustable, but whatever. I said "its strange that the charge would be high, haven't touched it in 5 years, bla bla" and said something along the lines of as the compressor gets a little bit more wear and tear on it "it doesn't pull as much vacuum as it used to" and that would cause the higher-than-normal pressure in the system. didn't really make sense in my head, but he sounded like he knew what he was talking about/not pulling it out of his ass. can anybody substatiate this? or at least know what the hell he's even talking about?

in any case, he said he spent about half an hour driving/testing it and thinks its fixed but wants to drive it a little more before turning it back over.

tia
Paul

OverkillZJ
07-08-2005, 06:24 PM
....vacume? adjustible switch, huh?

Hope it's fixed, but if it's wasn't a trusted source I'd say BS right off the bat. None the less, I hope it's fixed :partyman: