elbarto

I know there are a bunch of ac related questions around here and ive xhexked a bunch of them and can't find an answer to my question... anyways ive got a 98 cherokee sport. the ac hasnt worked since i bought it a few years ago but i decided to give it a go today and see whata wrong. the compressor has never kicked on since ive owned it. i stuck a can of refregerant with a gauge on it and it showed around 25 to 30 psi. i started shooting some into the system and i got the compressor to kick on. it started short cycling and the pressure gauge would drop to about 0 when the compressor kicked on. the gauge would then climb back up after a few seconds. i added some more till it read about 45psi with the compressor not running. does this mean its low and if so why does it read highee pressure when off? btw its still short cycling... i think i only added a small amount so far.

or do i have some othee issue.

anyways thanks in advance for any help

96fsxj

I am by no means an AC expert but it sounds like it. I think you want to shoot for 35-40 on the low side for pressures depending on ambient temps while the compressor is running.. Dont think it matters much what the pressures are while the compressor is disengaged. If it were me i would keep adding til you get the compressor to stop cycling and get good pressures or cold air.

macgyver35

Okay. Here's the long and short of it...

Yes, it's low. And if it's low or empty, you've had or currently have a leak.

You added enough freon to get the clutch to engage, but you're going to need to put a total of 1.25 pounds in to get a full charge. You've managed to get enough in to pass the low pressure cut-off switch's lower limit of approx. 38 PSI (I have a 98 and the factory service manual for it). But when the compressor kicks on it lowers the pressure on that side of the system and you get shut off again by the low pressure switch. Thus, the short cycling.

First, you need to determine if you still have a leak. You can do this two ways.

1)You can put freon in, take a pressure reading, then wait 48 hours and see if the pressure has dropped (or just listen for leaks if they are large enough). If it has, you've got a leak. You can put some UV dye in the system (they sell kits) and see if you can locate the leak yourself.

2) You can pull a vacuum on the system, either yourself if you have a vacuum pump (which I assume you don't or you'd likely be an ace at AC diagnosis) or you can go to an AC shop and have them pull a vacuum. If it doesn't hold, they put a little freon in and sniff around with a sensor and locate your leak for you. Probably cost you $50 to have this done. If the vacuum holds, they charge it for you. The added cost of freon will probably bring the bill up to $75.

If you go the DIY route of leak detection and repair, and you have addressed and corrected any leaks, here is the most important part. Have a shop pull a full vacuum on the system and have them charge it correctly.

There are a ton of guys on here who will tell you just to blow freon through the lines or some other BS, but be sure to have it done right. Their shortcuts may get it working half-a**ed, but the only way to have it working properly and at peak efficiency is to have a vacuum pulled. It's funny, these same guys would never argue that running your tires at 20 PSI on the highway is a good thing for your tread life or fuel efficiency, but they are quick to shortcut the vacuuming process. It confounds me why they would tell anyone to take a shortcut that they know will result in poorer performance. Anyway...

Pulling a vacuum before adding freon, will suck any regular air out of the system so that once you put the freon in you have a "pure" charge, which improves the efficiency and how well it cools. The vacuum will also boil off any moisture that may have gotten in the system (humidity in the air will deposit moisture in the system. Moisture can damage AC components and also hampers efficiency.

Good luck to you!

rrich

Ha Ha- Another self styled "expert" that has fallen for the hype -- .

"""""There are a ton of guys on here who will tell you just to blow freon through the lines or some other BS, but be sure to have it done right. Their shortcuts may get it working half-a**ed, but the only way to have it working properly and at peak efficiency is to have a vacuum pulled. It's funny, these same guys would never argue that running your tires at 20 PSI on the highway is a good thing for your tread life or fuel efficiency, but they are quick to shortcut the vacuuming process. It confounds me why they would tell anyone to take a shortcut that they know will result in poorer performance. Anyway...

Pulling a vacuum before adding freon, will suck any regular air out of the system so that once you put the freon in you have a "pure" charge, which improves the efficiency and how well it cools. The vacuum will also boil off any moisture that may have gotten in the system (humidity in the air will deposit moisture in the system. Moisture can damage AC components and also hampers efficiency.
"""""

But it's true - in part - it will make a difference.
Evacuating it before charging does get a slight amount more Freon in by removing the small amount of air in it instead of purging.
The difference? MAYBE noticeable with a thermometer in the vent - from 36 degrees down to 35.
TRY IT!

Properly purging it also blows out any water.

If it's open open for a long time - months - it should be flushed with cleaner to get the dirt out.

macgyver35

Well, rrich...

I'll say that in my relatively short time on these forums, it has become clear to me that you are the absolute authority on everything, and the rest of us are just idiots. So I guess we'll all just bow down to you from now on.

Not to put too fine a point on it, but I have seen a number of your posts where you use verbiage that is derogatory and insulting to other members. There are better ways to disagree with people and open a dialog that benefits everyone. Your approach tends to turn people off and they just stop listening to you, even if you're right. We're all on here to learn a few things, try to help others, and build a sense of community based on a common interest. Some, however, like to treat this forum as an opportunity for verbal sparring all too often. I've seen you called out in threads a couple of times in recent weeks for your attitude, and I guess it's my turn to do the same.

If you don't agree with me or others, that's fine. But treat the members of this board with a bit more respect. I, for one, have refrained from referring to you as a know-it-all blowhard.

I have no doubt that you have a great deal of knowledge to share that can benefit the group. Just try to share it in a way that isn't insulting and discounts the viewpoints of other members. You have an opportunity here to be viewed as someone who is a good teacher, but that won't happen if you take the approach of a heckler.

Lastly, until I see all the auto AC service companies out there start throwing their vacuum pumps in the dumpster, I'll stand by my previous statements about vacuuming being the proper way to charge a system.

rrich

AC shops are NOT going to throw them in the dumpster. Not as long the bull makes them profit.

Remember when there was the great crush to convert from R-12 to R-134?
A shop's typical conversion ran close to $1000 - they loved to scare you into replacing most everything.
Rumors like - even a tiny trace of 12 left in mixing with the 134 would EXPLODE!
Or they would plug up the system.
Or leak out right away.
Compressors would self destruct, Condensers would blow up, evaporators would leak and kill you, dryers/accumulators had to be changed (still a good idea when converting,) and of course the best profit of all - all the O rings had to be changed!

All kinds of bull to get you to pay them big bucks - for no reason.

That bull carried on to just refilling it too!
The AC shops still promote all that stuff.

The fact it has to be pumped down for it to work right is still a holdover from all that.

Reality - remember if air is in it, it's at atmospheric - there isn't much room for it so there's very little.
When putting in Freon it's way above atmospheric - cramming it in. The percentage of air left in - even if you didn't purge it is very minimal.
t much room for it - the entire system holds LESS than one lungfull of your breath. A quick purging with Freon gets almost all of the air out.
Then when you fill it you are putting much much more FREON in - under pressure - cramming it in.
The end result, evacuating vs purging makes very little difference, if any.

TRY IT AND SEE FOR YOURSELF!

Reality - the only thing that does not mix properly is the oils if converting. The old mineral oil should be flushed out. R-134 uses PAG oil. They will gum up - if there's any doubt whether all the old oil is out - the safe way is use ESTER OIL. - it's compatible with both.

Interesting - small leaks are not usually detected by pumping it down - a major leak won't hold vacuum. But where is it leaking FROM? All it tells you it's leaking. Besides the AC SYSTEM is under PRESSURE, NOT VACUUM.
dyes might - but they usually have sealant in them. And usually it's leaking where you can't see the stain.
Best way - electronic leak detector - ebay has them for about $20 - and last for years. Compare that with a can of Freon.

When you fall pray to rumors you need to know it - or go merrily on your way showing the world you haven't a clue.

People come on here for help - not to be led astray by folks who pretend to know.

macgyver35

1) You're taking examples of fleecing by some shops during the transition from one type of refrigerant to another, and trying to include in that the time honored and tested concept that vacuuming the system down results in optimal performance and helps to greatly reduce the chance of complications from air or moisture in a system.

2) Say what you will, but I am never telling anyone to do something wrong if I suggest they get their system vacuumed down per a standard practice that is based on physics. If it does no harm to the system, and in fact provides possible advantages, you simply can't say it is wrong to do it that way. Period. So stop trying to make me out to be either an idiot or a villian by insinuating that I'm giving people bad advice.

3) There is often more than one way to go about something. Your way may work, but mine (you know, the way nearly everyone does it, including the manufacturing plant where no end users are in witness to get fleeced for "extra profit") works too. And in my opinion, is the better way to go about it. It's the way I did it to my own vehicle, and I have ice cold AC that works flawlessly even in 95 degree heat in slow moving traffic.

4) Your final few sentences make may point about your tendency to insult and degrade far better than I ever could.

I'm not going to argue this with you anymore. The poor OP, who just wanted to get some help with his AC, is probably more confused now than ever. He can take my advice, your advice, or neither.

Jrock(fos)

If the compressor has never been replaced and the seals never been broken and it's empty there is a leak. I had the same thing with mine. The easiest way for me to find the leak for me was soap and water. See where it bubbles. You can fix the leak, but for the AC to run correctly and have the luxury of it in this hot summer, have it serviced and evacuate the lines. Even if it's empty it gets the water and crap out of it. The service costs about 60 bucks and you gotta pay for the freon on top. I had mine evacuated and filled for about 110 at Midas. Worth a Benjamin I'd say you can go through a bunch of the AC refill cans and it will be a waste until you find the leak. Save yourself the hassle.

rrich

""""Reality - remember if air is in it, it's at atmospheric - there isn't much room for it so there's very little.
When putting in Freon it's way above atmospheric - cramming it in. The percentage of air left in - even if you didn't purge it is very minimal.
not much room for it - the entire system holds LESS than one lungfull of your breath. A quick purging with Freon gets almost all of the air out.
Then when you fill it you are putting much much more FREON in - under pressure - cramming it in.

The end result, evacuating vs purging makes very little difference, if any.

TRY IT AND SEE FOR YOURSELF!"""""

Of course you HAVE TRIED IT!?

I have - many times. Being in he AC business - now retired - I still have 3 vacuum pumps.
I suppose you suggest completely deflating a tire before filling it - so you'll get more in?

Soap bubbles - explain how it could make soap bubbles if it was totally devoid of any pressure? If it still had enough to make bubbles - it has not let air in - it still has some Freon left.

But, fall prey to the bull if you believe it. The economy needs your money.