2002 Grand Cherokee A/C Blues - Page 3 - JeepForum.com
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post #31 of 41 Old 06-18-2021, 09:14 PM
WJ60
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Originally Posted by skatulaki View Post
Ok ! It is still blowing as cold as it was, and its a real relief this week let me tell you. Anyway I re-read all the posts, and I actually learned something I didn't catch on to before about pulling the vacume, and about air and moisture in the line.
So let's see if I've got the right thought process going !

I install a new main hose, which on installation, is obviously full of atmospheric pressure "air" and "humidity", and not refrigerant.
So a source of air in the line is automatically present from that installation ?
Second, I bought a brand new set of gauges, which were also obviously full of atmospheric air and humidity. Source of air number two !

Am I correct with this observation? Am I correct or on the right track, that the vacume pull is to get air and moisture out of the system without removing the refridgerant? I previously did not understand just what the vacume pull was supposed to accomplish .

Also I should probably do this pretty soon ?

Yes, yes, and yes.
Before charging the system a vacuum has to be pulled using a vacuum machine. After evacuating the gauges should be shut off and you should watch the blue gauge for at least thirty minutes to verify it does not move up towards 0. If it does you have a leak(s). If it holds the vacuum then hook the charging hose up to a freon can and use the freon to bleed the air out of the charging hose. Doesn't take much. You'll smell the freon. Then you can charge the system. If you have to use a second can then close off the gauges and hook up the second can and bleed the hose again.
When charging a system that's in a vacuum you want to charge liquid freon into the high side of the system. If the total charge can't be put in the high side, then start the ac up and charge the remaining freon into the low side while the compressor is running.
Air in the system drives the high pressure up higher than it should be. Moisture can freeze at the metering device and plug the flow of freon.

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post #32 of 41 Old 06-18-2021, 10:17 PM
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Does it get colder as you take off from a stop?
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post #33 of 41 Old 06-20-2021, 04:43 PM Thread Starter
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I have been watching some video's, and one thing I am confused about is whether or not I need to remove the refridegerant in order to pull a vacume ? Most video's showed people pulling a vac after replacing a compressor while the system was already empty. There was one video of a guy recovering the 134 ( out of a jeep actually ) but many of the comments suggested that while his effort was good , he wasn't doing it right. Recovery equipment is a pretty good chunk of $$$.
I need to clear this up before I go any further as to whether or not I have to extract the the 134 thats in there before pulling a vac ? ( I realize I probably look stupid, but I'm really trying to understand how all this works, I think I'm getting there.)

@ WJ60 You gave me 3 yes answers on my 4 questions, so I am not sure which one you didn't reply to? I would like to clear this up before going to the next step.

I was bumbling around AutoZone today waiting for my laundry to dry, and I inquired if they had the vacume pumps. They said they do not directly sell them on the shelf but they have them for use. Basically they charge you $200 and if you bring it back they give your money back, if you keep it, its yours, pretty fair deal if you ask me. The one they had in stock was leaking the oil, so I couldn't get one today, they said they would rectify that.
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post #34 of 41 Old 06-20-2021, 04:55 PM
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normally, the system is drained (they suck out the refrigerant and save it to reuse) after the system is drained, you pull vacuum. the shop (or you, if you have recovery/recharging tools) will then recharge the system, to factory recommended weight of refrigerant, and run it to test it. i'm thinking wj60 works in an a/c shop, so his knowledge reins supreme.

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post #35 of 41 Old 06-20-2021, 05:21 PM Thread Starter
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Originally Posted by Golden-Arm View Post
normally, the system is drained (they suck out the refrigerant and save it to reuse) after the system is drained, you pull vacuum. the shop (or you, if you have recovery/recharging tools) will then recharge the system, to factory recommended weight of refrigerant, and run it to test it. i'm thinking wj60 works in an a/c shop, so his knowledge reins supreme.
I do NOT question his knowledge, I am questioning what I have or have not learned and if I understand it properly. Some commenters on the videos have implied that pulling a vacume means pulling the refridgerant out and creating a vacume to let air and moisture out of the system, then charge back up. The procedure itself seems simple enough, The conditions to perform the procedure are what I have questions about. I want to learn correctly.

Last edited by skatulaki; 06-20-2021 at 05:30 PM. Reason: more information
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post #36 of 41 Old 06-20-2021, 06:16 PM
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If you try to vacuum the system before reclaiming the Freon then alot, if not all, of the oil in the vacuum pump will blow out of the exhaust port in the pump. Vacuum pumps are designed to hook up to systems that are sitting at atmospheric pressure.
I understand your desire to learn and work on your ac system but you really should take it to a shop. Most HVAC techs take a minimum of 1-2 years of training (in excess of $20,000) before working out in the field. There is a lot of harm that can occur if not done exactly right. Not only to the system but to you.

I should have suggested it, after reading your initial post, but if the system was empty of Freon for more than a week, then everything should have been replaced. The entire system. Contamination in a system containing POE oil is the ultimate killer. The only other option besides a complete replacement, is to run flush through every component and hoses.
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post #37 of 41 Old 06-20-2021, 06:45 PM Thread Starter
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If you try to vacuum the system before reclaiming the Freon then alot, if not all, of the oil in the vacuum pump will blow out of the exhaust port in the pump. Vacuum pumps are designed to hook up to systems that are sitting at atmospheric pressure.
I understand your desire to learn and work on your ac system but you really should take it to a shop. Most HVAC techs take a minimum of 1-2 years of training (in excess of $20,000) before working out in the field. There is a lot of harm that can occur if not done exactly right. Not only to the system but to you.

I should have suggested it, after reading your initial post, but if the system was empty of Freon for more than a week, then everything should have been replaced. The entire system. Contamination in a system containing POE oil is the ultimate killer. The only other option besides a complete replacement, is to run flush through every component and hoses.
So now you give up up your lessons? Ok, be that way ! It's all right I'll learn from somebody else! You are not the only tool in the shed ! What is your problem? I'm not going into business!
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post #38 of 41 Old 06-20-2021, 06:53 PM
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You're reading emotions into the reply that aren't there. There's a basic rule with all public forums: if some answers offend you then don't ask questions. I'm going to take a wild guess and say your a young person. I'm not bent out of shape over this, just trying to help. I'll try my best not to answer any future questions you might post.
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post #39 of 41 Old 06-20-2021, 07:03 PM Thread Starter
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Originally Posted by WJ60 View Post
You're reading emotions into the reply that aren't there. There's a basic rule with all public forums: if some answers offend you then don't ask questions. I'm going to take a wild guess and say your a young person. I'm not bent out of shape over this, just trying to help. I'll try my best not to answer any future questions you might post.
Actually I'm a 60 year old guy who cannot afford to go into shops and piss away money on phony repairs. I like to do my own work, like I have done my whole life! You have been great help so far, then you unilateraly decided that it was in my best interest to go to a shop! Well I am not giving up now, maybe you are, but I am not!

finish helping, or dont finish the job, thats on you ! It is you who it will reflect on!

I'm going to let this pass, as a little bit of short attention span , and some frustration with ignorance on both our parts!

Lets try again please?

Last edited by skatulaki; 06-20-2021 at 07:14 PM. Reason: more information
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post #40 of 41 Old 06-23-2021, 10:12 PM Thread Starter
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This sites timeout sucks ! I spent several minutes typing out a polite gesture to WJ60 asking what I did that offended him , and apologizing for some offense I didn't think I committed, I'm not going to type it all again !
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post #41 of 41 Old 06-24-2021, 06:41 PM
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Originally Posted by skatulaki View Post
I do NOT question his knowledge, I am questioning what I have or have not learned and if I understand it properly..

i didn't say, or imply that. i was merely stating that i believe wj60 works in an a/c capacity, and his knowledge is reliable. if you got anything from that, other than what i just posted, well, that's on you.



you need to lighten up, francis.




the very real fact is, you need some specialized (expensive) equipment to work on the a/c system. that equipment requires training. at some point, with almost any repair, you have to decide between the cost of a repair at a shop, vs. the expense of acquiring everything you need to do it yourself. sometimes you win this bet, sometimes it's the shop. if it costs 250 bucks at the shop, and it costs you 1000 bucks to get the equipment to do it yourself, which is the better investment? if you're going to use the equipment more than 4 times, it might be worth it to buy it. using it just once? that should be a no-brainer.

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