Ac low side pulling a vacuum
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
For diagnostic purposes, you can try back-flushing the liquid line, the condenser and the high pressure line. Disconnect each at both sides/ends.
If any are clogged, replace it. Plan on replacing the condenser as a likely step anyway. If it or the high pressure line is clogged, they will need to be replaced as neither can be effectively cleaned out.
If any are clogged, replace it. Plan on replacing the condenser as a likely step anyway. If it or the high pressure line is clogged, they will need to be replaced as neither can be effectively cleaned out.
Tuned
Joined: Feb 2015
Posts: 323
Likes: 12
From: Tulare, CA
I have a dumb question for you. Is/was your truck operated in a dirty or dusty environment? The previous owner of my truck owned orchards and drove the truck through them a LOT. The dirt & dust plugged up the evaporator cooling fins. I don't know if this is your problem or not or can even be related to your issues. I do know it's not too difficult to check. The inner fender well has to come out and the evaporator case then splits in half to check. I did check mine not too long after I bought it to check on it and wash off the evap core. I do know if the evaporator is plugged the high side will be through the roof but that's all I know (or was told anyway) This info might not do you any good but it doesn't hurt to ask an A/C person.
Moderator
Joined: May 2004
Posts: 6,517
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From: Home Base Nebraska
If you can flush through the evaporator and condenser and they are both externally clean and with a new orfice, can't remember if they have a filter dryer that should also be changed. Then your problem is the valves inside the compressor are bad. Bad valves will cause low suction pressure and high head pressure depending on what one failed.
Denny
Denny
Cargo Master
Joined: Jul 2009
Posts: 2,541
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From: Des Moines
Well that didn’t fix it , after flushing the evaporator out and pulling a vacuum for 30 min I put in 33-35 oz of Freon while I was putting it in the pressure was at 45 low side 350 on the hi side , as soon as I finished the low side slowly dropped down to a -3 vacuum . I replaced the orifice tube again also . On the back side of the orifice (closest to evap) the line had frost on it but the large line coming out was not cold and the air wasn’t cold . Is that Saying the evap is plugged even after I flushed it ? Or is it something else plugged ?
In a properly charged and correctly operating system, the evaporator outlet line and the compressor suction line off the accumulator will both be relatively the same temperature.
The frost on the evaporator side of the orifice tube might be an indication that the incorrect tube is installed. If it is the correct tube, then most likely the evaporator is plugged.
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Trailering
Joined: Jan 2021
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Ok this evening me and my 16yr old son unhooked the hoses to the condenser, evaporator and compressor isolating them and flushed them out . We then added 7 ozs of pag oil . It was a guess how much I lost when flushing out everything but it calls for 9 ozs of pag oil to total . We then pulled a vacuum of 29ish lbs for about a hour and 15 min on entire system . Let it set for another 20 min and no loss of vacuum . We added 3 12 oz cans I’d Freon , the system calls for 2 lbs 10 oz of Freon (42 oz’s ) at the I hooked up the 4th can and started to add the 1/2 of it and my son tripped on a hose and I went over to check on him. While I was doing that it emptied the 12 oz can so it now has 3 lbs of Freon in it . The compressor will run for 5 seconds and shut off for 2 seconds . Pressure on low side goes from 20-50 in that 5 seconds then takes 2 seconds to drop to 20 again . High side pressure goes from 175 -250 in that time period . Air is cooler but not cold . Do I need to take out the 6 ozs of Freon , or add more lol . I took a video of the gauges but not sure if or how I can share it here
Cargo Master
Joined: Jul 2009
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From: Des Moines
Where are you finding the capacity? In your first post you said it takes 34 oz - now you say it takes 42 oz.
According to prodemand.com it takes 45 oz.
If there’s no label under the hood, check the capacities and specifications page in the owner manual.
There is a little “wiggle room” on the capacity because the accumulator can store a certain amount of extra refrigerant, but if it’s significantly overcharged, the clutch on/off time and cooling effect you describe is an indicator of an overcharged system.
Verify the capacity before adding or removing from the system.
According to prodemand.com it takes 45 oz.
If there’s no label under the hood, check the capacities and specifications page in the owner manual.
There is a little “wiggle room” on the capacity because the accumulator can store a certain amount of extra refrigerant, but if it’s significantly overcharged, the clutch on/off time and cooling effect you describe is an indicator of an overcharged system.
Verify the capacity before adding or removing from the system.
Ok this evening me and my 16yr old son unhooked the hoses to the condenser, evaporator and compressor isolating them and flushed them out . We then added 7 ozs of pag oil . It was a guess how much I lost when flushing out everything but it calls for 9 ozs of pag oil to total . We then pulled a vacuum of 29ish lbs for about a hour and 15 min on entire system . Let it set for another 20 min and no loss of vacuum . We added 3 12 oz cans I’d Freon , the system calls for 2 lbs 10 oz of Freon (42 oz’s ) at the I hooked up the 4th can and started to add the 1/2 of it and my son tripped on a hose and I went over to check on him. While I was doing that it emptied the 12 oz can so it now has 3 lbs of Freon in it . The compressor will run for 5 seconds and shut off for 2 seconds . Pressure on low side goes from 20-50 in that 5 seconds then takes 2 seconds to drop to 20 again . High side pressure goes from 175 -250 in that time period . Air is cooler but not cold . Do I need to take out the 6 ozs of Freon , or add more lol . I took a video of the gauges but not sure if or how I can share it here
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Moderator
Joined: May 2004
Posts: 6,517
Likes: 917
From: Home Base Nebraska
Ok this evening me and my 16yr old son unhooked the hoses to the condenser, evaporator and compressor isolating them and flushed them out . We then added 7 ozs of pag oil . It was a guess how much I lost when flushing out everything but it calls for 9 ozs of pag oil to total . We then pulled a vacuum of 29ish lbs for about a hour and 15 min on entire system . Let it set for another 20 min and no loss of vacuum . We added 3 12 oz cans I’d Freon , the system calls for 2 lbs 10 oz of Freon (42 oz’s ) at the I hooked up the 4th can and started to add the 1/2 of it and my son tripped on a hose and I went over to check on him. While I was doing that it emptied the 12 oz can so it now has 3 lbs of Freon in it . The compressor will run for 5 seconds and shut off for 2 seconds . Pressure on low side goes from 20-50 in that 5 seconds then takes 2 seconds to drop to 20 again . High side pressure goes from 175 -250 in that time period . Air is cooler but not cold . Do I need to take out the 6 ozs of Freon , or add more lol . I took a video of the gauges but not sure if or how I can share it here
Denny
Cargo Master
Joined: Jul 2009
Posts: 2,541
Likes: 54
From: Des Moines
FYI, oil is circulated through the system with refrigerant - it doesn’t just remain in the compressor except for 2-3 ounces, if that much. That’s why it’s recommended to add oil after the condenser, evaporator or accumulator are replaced - because it’s expected a certain amount of oil is trapped in them. The idea is to have at least some oil at every point in the system to ensure that the compressor stays adequately lubricated.
While it’s true that excessive oil can affect system operation, the accumulator is designed to store additional oil and meter it back to the compressor as refrigerant is pulled in. I’d have to find my old notes to be sure, but I recall learning that it takes something in the neighborhood of 1.5 times oil capacity to affect an accumulator based system.
Given the OP’s description, I think it’s unlikely that it’s overcharged on oil.
While it’s true that excessive oil can affect system operation, the accumulator is designed to store additional oil and meter it back to the compressor as refrigerant is pulled in. I’d have to find my old notes to be sure, but I recall learning that it takes something in the neighborhood of 1.5 times oil capacity to affect an accumulator based system.
Given the OP’s description, I think it’s unlikely that it’s overcharged on oil.
The only way to adjust your oil level is to flush the system and drain all the oil out of the compressor then add the recommended amount. A normally operating system has very little oil vapor out in the system, the oil belongs in the compressor not out in the system. A oil logged system will never operate properly and it will destroy the compressor because it can't compress fluids. Don't guess know for sure.
Denny
Denny
5th Wheeling
Joined: Oct 2012
Posts: 28
Likes: 3
Oil logged
FYI, oil is circulated through the system with refrigerant - it doesn’t just remain in the compressor except for 2-3 ounces, if that much. That’s why it’s recommended to add oil after the condenser, evaporator or accumulator are replaced - because it’s expected a certain amount of oil is trapped in them. The idea is to have at least some oil at every point in the system to ensure that the compressor stays adequately lubricated.
While it’s true that excessive oil can affect system operation, the accumulator is designed to store additional oil and meter it back to the compressor as refrigerant is pulled in. I’d have to find my old notes to be sure, but I recall learning that it takes something in the neighborhood of 1.5 times oil capacity to affect an accumulator based system.
Given the OP’s description, I think it’s unlikely that it’s overcharged on oil.
While it’s true that excessive oil can affect system operation, the accumulator is designed to store additional oil and meter it back to the compressor as refrigerant is pulled in. I’d have to find my old notes to be sure, but I recall learning that it takes something in the neighborhood of 1.5 times oil capacity to affect an accumulator based system.
Given the OP’s description, I think it’s unlikely that it’s overcharged on oil.
Moderator
Joined: May 2004
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From: Home Base Nebraska
I see this all the time on older vehicles. The system has too much oil and cannot function. BLow everything clean again, (i use 91% rubbing alcohol and compressed air) and put it back together and add only freon. The compressor will have all the oil in it, the system needs. The oil is so thick it's slowing down the freon going through the orifice tube, causing the low side vacuum and the high side pressure. I get 20 a year in here doing it. Normally it destroys the compressor from high pressure, or blows the high pressure line. Some systems have a pop off valve on the compressor that will open at 600 psi and vent freon into the atmosphere.
You almost had it the last time you blew everything clean, until you added the 9 Oz of oil back into the system. Your compressor is full of oil, it has all the system needs. Blow everything else clean and put 40 Oz freon in, and it will freeze your *** off.
You almost had it the last time you blew everything clean, until you added the 9 Oz of oil back into the system. Your compressor is full of oil, it has all the system needs. Blow everything else clean and put 40 Oz freon in, and it will freeze your *** off.
Not much to add..
Denny
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