So my ac works pretty good, but lately at stop lights and idle, it's not as cool as it used to be. Clutch is working, electric fan is working and i have the hd cooling and the mechanical fan is working. Condenser is clean. I have a cheapo low side gauge. I checked the low side at idle with ac on max and windows down. Outside temp was 110 f. Low side was reading like 60 psi. Too high. I have never charged the system before. Previous owner had engine replaced so i figured they had over charged it. Let out some Freon and its hovering around 50 now. It is better, but still not what it used to be. My issue is when revving the engine a bit my low side pressure goes up, on other cars i worked on, revving the engine lowers the low side psi. It's weird because at speed while driving, ac gets colder. Could i have a restriction somewhere? Or is my compressor going? I know i need a good gauge set. Had the car in for an alignment and the place offered an ac check. Thought awesome, will have them check the system. Most places offer a free performance check, hook it up check the high and low side. Guy made me mad, told my wife, "oh we don't recommend that, we want to discharge and recharge the system. Checking the readings won't tell us anything." I told her not to have it done. Wanted to charge $60. I know checking high and low side can tell you allot, help you diagnose it.
Ac issue
- Thread starter nlocascio
- Start date
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tjkj2002
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You will need to know the high and low side readings,no way around it and the proper charge amount will have to be in the system also.
Birdman330
Full Access Member
An independent shop will most of the time do a quick check. Most major shops like where I worked at wouldn't do checks, just a full service with die to see if there were any problems.
uss2defiant
Full Access Member
i'd like to say that it is an AZ issue.
Don't know but I have the same issue.
Don't know but I have the same issue.
Thanks for the info. Will take it to a small local shop. I would think the readings would help you see if compressor is working as it should or if there is a restriction. If they evac and refill system to only find out that the compressor is bad, they would just have to evac again. Funny thing is the shop i was at did offer a check, but basically refused to do it, wanting to immediately charge me more than what they listed on the wall
adamkrz
Full Access Member
First of all a car a/c system is different from all others, at idle your compressor is running much slower therefore less btu's and a higher suction psi.
A proper charge would require a full evacuation with a vacuum pump and recharge by weight. I've seen systems charged without being evacuated cause all kinds of problems because of contaminates in the system.
A proper charge would require a full evacuation with a vacuum pump and recharge by weight. I've seen systems charged without being evacuated cause all kinds of problems because of contaminates in the system.
Taking it in Wednesday, so we'll see what happens. Local shop with good reviews. No chain shop this time. I'm not into the bait and switch. If you don't feel it is a good service, don't offer it in the first place. I like a place that is up front and honest. Some places like to talk down to you, make you leave there feeling stupid instead of informed. Will update on what they find. Thanks for all the info. I do try and run fresh air as well as recirculate. Doesn't make too much of a change. The shop i was at first just said, "oh it's normal because it's so hot". Not true. Ac used to perform better in same heat. This is the shop that also said they couldn't align the front end because I came from Ohio with it and they don't have a torch to heat it up. Lol we have lots of snow birds here from snowy states and rust, what shop doesn't know how to get a nut broken loose lol had to take pb blaster and do it myself. Ooh well... Time to find a better shop
renegade 04
Full Access Member
If I were you I would have the system brought down to a vacuum and then recharge the system.
megatone
Full Access Member
This is probably the best way to go. Just because an a/c system has pressure does not mean the R134a chemical refrigerant is still active.
The only reasons to put a vacuum on an a/c system is to test for leaks and to remove the moisture in the oxygen molecules contained within the air inside the system.
When I do an a/c recharge, I will apply vacuum for an hour then bring the system back up to ZERO psi and then add the proper amount of R134a refrigerant.
Here's something to think about. Example: A common sized 20oz can of R134a contains 17 ounces of the R134a chemical and 3oz of additives. If your a/c system requires 34oz of refrigerant for peak performance, you need to add two of those 20oz cans to the system for a total of 40 oz.
Those 20oz cans that I am referring to are brand named "A/C Pro" available at all auto parts stores. The cost for one of those cans is $50 (US). VERY expensive per ounce. I do alot of a/c service out of my own home and when I buy R134a I get it in the 30 pound tank. The price for 30 pounds of this stuff is $200 (US). But think about this: 4 cans @ $50 each=$200 and in reality, you're only getting 68oz of R134a, where as for the same price, with the tank, you're getting almost 500oz. If the average car a/c system requires 40oz of the chemical.......I can service a dozen cars for $200 (with the tank), where as, with the small cans, I would only be able to do 2 cars with that $200.
If you're a/c temp is colder at higher engine rpm's but not as cold at idle (low rpm's), you may have a problem with the valve.......aarrrgh!!!!....I forget what the valve is called, but it's function is to (basically) hold back the (pressurized) liquified R134a right before it passes thru that valve and vaporizes.....becoming ice cold.
I hate when I forger things.
Whether your a/c system is low on R134a or not.....it will NOT have an effect on the cold air changing temperatures at higher engine rpm's vs lower engine rpm's because the amount of R134a is not fluctuating. Something else is going on.
Let me ask you this. When you shut off the vehicle with the a/c running......do you hear a hissing type of sound coming from under the hood? Kinda like the sound a tire would make if it has a slow air leak? If you hear the hissing sound right after you've shut off the engine while the a/c system was operating, this could.......this would indicate that the high pressure side of the system is leaking down, back into the low side of the system.
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Thanks very much for the info. I'm not sure about the sound, will have to check. I was thinking that something maybe stuck open or something. Ac had not been charged with auto parts store stuff. Was charged by the mechanic who replaced engine before i got the jeep 6 years ago. I haven't lost any pressure since i got it, just had performance issues at idle this year. Is that the valve or restriction device in the ac line? I read somewhere the one line needs to be replaced to do that
uss2defiant
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Hockeygoon
Full Access Member
Stupid question time. If you replace the condensor (and probably the air dryer) once its bolted together can you just refill with the WalMart A/C recharge?
Arctic Freeze Ready-To-Use Arctic Freeze Kit (California Only) - Walmart.com
Arctic Freeze Ready-To-Use Arctic Freeze Kit (California Only) - Walmart.com
megatone
Full Access Member
No!!! You will need to apply VACUUM to the system.....the vacuum tool costs right around $300.....you could borrow the vacuum pump from Autozone (giving them $300 deposit, which you will get back when you return the vacuum tool). The vacuum tool does two things...
#1)It insures that the system has no negative pressure leaks.......and
#2).....more.....most importantly, applying the vacuum, and holding that negative pressure for an hour draws out the super small molecules of moisture in the air which is inside the system. Just the smallest amount of moisture can kill an ENTIRE a/c system within one season of use. The moisture mixes with the R134a chemical and turns to acid.....the majority of an a/c systems 'hard components' are made of aluminum....which is what the acid attacks first.
You could just add the chemical to the system after that system has been opened, but you will NEVER get the amount of cold air that should be coming out of it, plus the system will be destroyed from the inside out....eventually.
dougmac
Full Access Member
I am an AC tech. Here is my advice,..
The guy that wanted to complexly evacuate and recharge you system was quoting the correct way to service your system. Today's CCOT systems have a very small refrigerant capacity and are very sensitive to having the proper charge. The only way to get the proper charge is to remove the charge and weigh the charge back in. You can do this without opening the system if you use a recovery machine. It is impossible to determine the amount of refrigerant in the system by simply looking at the gauge readings.
If the system is opened to the atmosphere, all of the moistue and air must be removed. To accomplish this, it will need to be drawn into a deep vacuum with a vacuum pump. You should draw it down to around 500 microns. Proper procedures must be followed to prevent any air from getting into the system when servicing it. Even a small amount of air in the system will affect the performance and can destroy the compressor.
The only thing in the system should be refrigerant and oil. DO NOT PUT ANYTHIG BUT PURE 134A IN THE SYSTEM!!! No added enhancers! No stop leak! No refrigerant with oil added! JUST PURE 134A!!! The only time you should add oil is when a component has been changed. The service manual will tell you how much to add for each specific component. An over-charge of oil will adversely effect the performance and is very difficult to correct. Chemicals other than refrigerant and oil are contaminants. Once these have been added, it makes it impossible to service your system without contaminating the recovery equipment. I cringe every time I look at all of the crap they sell to put into AC systems that doesn't belong in it. (dye for leak checking is my only exception to this rule}
You may get it to cool some without servicing it properly, but it won't perform well unless it is done right. These systems are built on the edge of being adequate and if things aren't completely up to par, you won't get good results.
The guy that wanted to complexly evacuate and recharge you system was quoting the correct way to service your system. Today's CCOT systems have a very small refrigerant capacity and are very sensitive to having the proper charge. The only way to get the proper charge is to remove the charge and weigh the charge back in. You can do this without opening the system if you use a recovery machine. It is impossible to determine the amount of refrigerant in the system by simply looking at the gauge readings.
If the system is opened to the atmosphere, all of the moistue and air must be removed. To accomplish this, it will need to be drawn into a deep vacuum with a vacuum pump. You should draw it down to around 500 microns. Proper procedures must be followed to prevent any air from getting into the system when servicing it. Even a small amount of air in the system will affect the performance and can destroy the compressor.
The only thing in the system should be refrigerant and oil. DO NOT PUT ANYTHIG BUT PURE 134A IN THE SYSTEM!!! No added enhancers! No stop leak! No refrigerant with oil added! JUST PURE 134A!!! The only time you should add oil is when a component has been changed. The service manual will tell you how much to add for each specific component. An over-charge of oil will adversely effect the performance and is very difficult to correct. Chemicals other than refrigerant and oil are contaminants. Once these have been added, it makes it impossible to service your system without contaminating the recovery equipment. I cringe every time I look at all of the crap they sell to put into AC systems that doesn't belong in it. (dye for leak checking is my only exception to this rule}
You may get it to cool some without servicing it properly, but it won't perform well unless it is done right. These systems are built on the edge of being adequate and if things aren't completely up to par, you won't get good results.
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How much of a vacuum do you have to pull prior to recharge? Not familiar with the micron unit.
adamkrz
Full Access Member
Couple of things to correct you guy's.
1- You break the vacuum with refrigerant - Do not bring it to zero and then refill.
2- A vacuum of at least 29" inches is needed to remove non - condensables from the system; Mostly nitrogen and moisture and what ever else is in the air.
3- If your changing the condenser, evaporator or compressor you must know how much Pag oil was in each and add as needed, Very Important .
4- A proper shop will also have a reclaimer to remove what you have in the system to filter and re-use.
5 -R134a systems are more sensitive to the correct charge than the older r12 .
1- You break the vacuum with refrigerant - Do not bring it to zero and then refill.
2- A vacuum of at least 29" inches is needed to remove non - condensables from the system; Mostly nitrogen and moisture and what ever else is in the air.
3- If your changing the condenser, evaporator or compressor you must know how much Pag oil was in each and add as needed, Very Important .
4- A proper shop will also have a reclaimer to remove what you have in the system to filter and re-use.
5 -R134a systems are more sensitive to the correct charge than the older r12 .
Okay so 29 inches of mercury would convert to 500mtorr so mtorr is micron. Got it.
dougmac
Full Access Member
29" Hg = 20,000 microns This is not a deep vacuum. You should get below 750 microns which is 29.89" Hg. 500 microns is better.
You need a micron gauge to properly measure a deep vacuum. A compound gauge is not adequate. As you can see one inch Hg is over 20,000 microns.
