Alright thanks man. I am probably gonna have to try this as my compressor doesn't like to stay running unless I keep a paperclip in the low pressure switch.

 

If that's the case the clutch isn't the problem. Mine wouldn't turn with the lo bypassed. Yours sounds like you just don't have enough freon in the system. I'm by no means an ac guy. You need to have the low bypassed and then while the clutch plate( front center peice) is spinning that's when you put the charge in. It should empty your can. Mine took a two cans.

 

 

While a lot of your other information is correct, you've got this part wrong on air being in the system. Keep reading that AC book you have. When you decide to work on a system the proper way, then I'd be inclined to send people to your shop.

Air is something you do not want in an A/C system because it is a noncondensable gas. Air does not change from a vapor into a liquid at the kind of pressures that can be achieved by an ordinary compressor, so all it does it occupy space and displace refrigerant. The result is reduced cooling performance, evaporator freeze-up, intermittent cooling, increased compressor noise, higher than normal discharge pressures, and maybe even compressor failure. Air can get inside an A/C system a couple of ways. Air enters the system anytime the system is opened for service. If the system is not vacuum purged prior to recharging, air may still be inside when the refrigerant is added. Air can also enter through leaks. Even when the system contains refrigerant and is under pressure, some air and moisture will still get inside. I don't know why you would never put a vacuum on the system anyway not only to remove the air but to confirm that you have no leaks now. So you're charging systems without knowing they are 100% sealed? This to certain people would be called intentional venting if you think about it.


So, while you are doing "charges" to systems and not actually fixing them, I have to wonder how many of those customers come back and complain saying "yeah, it's cold but not THAT cold". Especially on really hot days. You might get by on charging it with air in the system, maybe when the ambient is below 85 degrees, but you'll have issues when it gets really hot and the head pressure sky rockets and the compressor shuts down. I see why other shops may have hated you. I always hated when people came to my shop to have me fix something that someone else didn't do correctly. The customers hate paying for stuff twice.

 

I recharged my AC yesterday because it just wasn't cold enough. Everything went fine and is blowing cold. My question is about the compressor. Before I added a can of refrigerant the compressor would cycle on (3-5 seconds) then off (for about 1 second). Now the compressor constantly runs when AC/defrost is on.

So... should the compressor run constantly or cycle on/off? I don't think I overcharged it (one 18oz. can)

1998 Cherokee SE with 125,000 miles.

 

The fallacy of air -
If you were to open the system and blow out all the freon out so it's only air left in the system - then close it you'd have a little air in it.
It would be at atmospheric pressure.
It could hold maybe 2 of air OZ at STP.
Now fill it with freon. - when you fill it with freon you have to force it in on top of the air to get any in. Typically you fill it to about 30 lbs. pressure static.
Now the actual VOLUME OF FREON is far more than the tiny bit of air left in. If you were to actually reduce the pressure down to where you had the air at STP you'd find the amount of air is only about 2% or less of the total volume of air and freon combined.

It's not unlike adding 2 drops of food coloring to a gallon of water - not much.

Yes, it will reduce the temp slightly = but by very little.
Can you tell the difference between 36 degrees and 36.72 degrees? 2%
If you do a quick purge it's even less.

Sorry you've fallen for all the bull.

You need to go take a physics class 101.

But go ahead and fleece your customers. lots of people do.

 

I agree. You also have to put a vacuum on the system to remove said air. Air contains moisture and moisture inside an AC system will cause damage. Please service these systems right. A home AC book or a Physics book does not apply here.

 

He He - Laws of physics don't apply to AC?

How much water do you think 2 OZ of air at STP can hold? 10 gallons?

How much water can that 2 OZ hold after you flush the air (and water vapor) out by purging with Freon?

Why did other shops hate us? We did not screw people like others did. We did not spout lies and falsehoods. The result was we ended up with more business than others, and the customer cost was much lower.
HONESTY DOES PAY OFF!

A typical AC service job-
Complaint - no longer blowing cold.
First we'd pull out the Freon it still had in it - if any.
Then we'd use air pressure (dry air) to pressurize the system. We'd usually use 50 lbs of pressure. Leaks don't always show up under vacuum in a system that uses pressure DUH!
If it held air pressure it should hold Freon.
if we found leaks we'd repair them as needed - and charged accordingly.
Then we'd release the air pressure.
next step was to add Freon. We'd shoot a little in the low side with a vacuum canister on the hi side to catch any freon expelled = EPA rules.
The flushing/purging with Freon would remove the vast majority of air. Since we'd used dry air there was very little moisture to be found, but the purging removed it along with the air.

Next - close the hi side - fill to specs using the customer's own Freon he came in with, plus however much more he needed
Then let it sit for a few minutes
We'd use 2 different types of electronic leak detectors to make sure we did not miss any leaks.

Finished -
then the part they hated us for:
We already cured and tested for leaks - doing it right we knew there was no more problems.

1 YEAR UNCONDITIONAL GUARANTEE AGAINST ANY LEAKS or other problems - like blowing warm etc.!
We even put the vent temps right on the invoice to compare it to in case of a complaint.
If it developed a leak we'd fix the leak and refill it AT NO CHARGE.
NOBODY OFFERS THAT KIND OF GUARANTEE!

That's the difference - other shops always came up with excuses as to why their work didn't last - always bull!

Sure, once in a while we'd have to eat a job - something we missed - but we stood behind the job no matter what. Even if we had to replace the evaporator the costliest type of comeback we'd do it with a smile.

After all - all a business has is it's customers - without them you have nothing.

 

Not starting an argument, but I've never had one complaint or problem doing it the old fashioned way or with the newer machines. Personally, blowing air into an AC system is something I'd never do or consider. But to each his own.

 

Well my compressor fix lasted a month or so.... The compressor bearings are squalling and the clutch slips now. I am hoping that is where my leak was. I plan on replacing my compressor with a used one I got for 65 delivered. How much oil do I put in it and what kind? It's a 99 4.0 auto. And, do I need to replace the receiver dryer or the orifice tube?

 

In an effort to get the AC to work in the 1998 4.0 Auto Jeep Cherokee Sport I just purchased with 324,000km, I had a similar issue. The first issue was the fan didn't work, no problem, I purchased a used one. The used one didn't work either. I picked up another fan, it may have been out of a Buick, but I installed it into the housing and used the Jeep fan blade. Great, fan works, but didn't come on. I checked the pressure with the engine off and it was really low. Not enough pressure to allow the fan/compressor to kick in. With a DIY kit, I put in about half a can, 30psi. Then I started the Jeep and put the AC on high. It went from 20psi-45psi as the compressor cycled and wouldn't pull any more. Once the engine got warm, it went to 75psi and didn't move, the compressor no longer cycles, and the AC doesn't blow cold.
Will 75psi cause damage?
If it holds 75psi for a few days, I'll take it to a shop to get evac and fill.
Somebody mentioned earlier that it will do this if there isn't enough r134a in the system. I don't want to try adding more with the pressure that high. It also seems that when it gets hot, the clutch loses its effectiveness. I'll keep you posted.
Please let me know your thoughts.

 

Seems like I have the exact same problem. I just checked the pressure again after letting it sit overnight. The engine was cold and the compressor was working great. I put in the other half of the freon canister and the ac worked great, until the engine got to normal operating temp. The pressure then jumped to 75-80psi and stayed there, the compressor stopped cycling. It's a Sanden compressor. I'll try to grab a clutch next time I go to the junk yard.

 

Sorry for hijacking your thread, but my personal opinion is to take it to a shop. You might also need a new orifice or expansion valve, and a new filter/dryer. They can check the chart in put in the proper amount of oil, and do a proper evac and fill. If you had a leak, the oil probably leaked out too killing the compressor. Not doing a proper recharge also could have killed the compressor. The shop is expensive for a reason, but it'll save you from doing it twice. I plan to have a professional fill/inspect mine as soon as I verify if the clutch is bad and make the repair.

 

1) Got some cans of R134 with standard hoses, nothing connects right on the fitting where you go to charge the system. Parts place told me the wrong fitting.

The filler hose appears too large for the fitting to put the freon in.

Info says to get a manifold which is about $100 to fill using a can of freon that costs about $12. ?? Is there a connector fitting you can get that connects from the freon hose to the a/c system?

Have a 98 Cherokee inline 6. Possibly the fitting on the a/c system isn't usual? Have the Haynes a/c manual and regular Haynes manual for the Jeep.

2) Also a/c hasn't been really cold this year. How do you bypass the cutout for the compressor.