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Procedure for changing high pressure switch? (A/C)

HMGanja

NAXJA Forum User
Location
N.C.
I have been having problems with my A/C feeling and sounding rough and got a high pressure switch (only $12) after having a good friend/mechanic look at it for me. I was just wandering if there is any special procedure for changing this switch, or if you just take the old one off and replace with new one. I am pretty mechanicly inclined and do all other work on my stuff, but have never had to mess with any A/C system. Thanks.
 
You can probably just remove and replace. FSM says you need a NEW oring lubed with the same type oil for the compressor. The oring is special for R134. Sounds to me though, like you are changing parts without diagnostics. And possibly inducing a leak where none exists now.
 
Should be as simple as screw the old one off and screw the new one on.

Good Luck

Nick
 
Stop the bus! Are you talking about the low pressure clutch cycling switch or the high pressure cutoff switch?

The low pressure switch turns the compressor on/off. They do sometimes go bad. The high pressure switch is a safety cutoff that turns off the compressor if the pressure gets too high, usually the result of overfilling or a blockage in the system. They hardly ever go bad. Also what year? What makes you think its bad?

The low pressure switch usually has a shraeder valve under it to hold the system pressure when you remove the switch. I say usually, because I once worked on a Mustang that didn't have a shraeder under there. Started unscrewing the valve expecting it to hold pressure and instead it started spewing freon. The o-ring got pushed out of place by the pressure and wouldn't seal again so I ended up dumping the entire system in the parking lot. Turns out the system wasn't factory installed, but rather an aftermarket installed by the dealer.
 
The Jeep is a '99 Limited. I am going by what my mechanic is telling me. Like I said, I have no A/C experience really. I told him what it was doing, he went out and looked at it while it was running, and of-course it done just fine when he was looking at it. But he said it could be the high pressure switch based on what I told him it was doing. So, thats what I got since it was so cheap I said F it, really wont hurt anything to try. But, I think I may wait to see if it actually keeps acting up. Since it only felt and sounded bad that one time. It sounded to me like the compressor was running really rough. But it was still blowing cold air. Thanks for the information people!
 
Good time to point out safety with A/C. I had a customer come in yesterday with an expansion valve in his hand. He said he was doing fine removing it until the freon began spewing out under pressure and soaked him.

I want to suggest that anyone doing work on A/C systems who doesn't have some training and a set of proper gauges is looking for an injury. It's just a little safer than changing a fan clutch on a running motor - just a little safer - since most of the diagnostics have to be performed on a running motor. A gauge set tells you what's up, not a guess at what may or may not be a symptom, and then blaming a part you didn't test.

My customers symptom was that the low side pressure was 108 pounds - not running. The compressor is also the suction motor for the low side, and if it's not running, no low side pressure is very accurate. So he basically dumped 4 pounds of R134 at $7.99 a can blaming the wrong part - a part not available except through his dealer.

You all think it through, surf for better answers, and be ready to let the pro's do the work, because honestly, even a great powertrain mechanic knows he could be kinda weak on A/C, and it's better to let the other guy get it done right the first time.
 
I second the notion let pros handle A/C work....venting Freon can cause major frostbite VERY quickly. That stuff comes out extremely cold (I don't recall the specifics off the top of my head, but suffice it to say that you can get second degree frostbite in seconds). I've seen guys think that they'll just barely crack a line open, and let it slowly vent without issue...problem is that as soon as they feel the freon, they instinctively jerk their hand back and get it caught in something letting the freon burn them for a good 20-30 seconds while they panic trying to get free.

It's not likely to happen if you're careful, but if it happens to you, you'll be in a world of misery for quite some time, assuming you're lucky enough to avoid amputation.
 
Well, I have officially been talked out of doing it period. If the the damn A/C quits, I have the expert change it. BTW For shats and giggles I priced a new compressor from Mopar....$480.....
 
Good plan. The other thing to keep in mind that I forgot to mention is the simple gauges that typically come with the do-it-yourself freon kits are almost useless. Since they only measure low side pressure, they're only telling you half the story. If there is something else wrong with the system, such as a partial blockage somewhere, you may never know it with that gauge. The system on my '91 is a good example. It shows approx 25psi on the low side, which is on the lower limit of OK. What it isn't telling me is the nearly 450psi the compressor is making on the high side, which is WAY too high. It's a sign of a blockage somewhere in the system. But just using the DIY kit, it would have me adding still more freon....
 
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