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Turbos4life

AC help low side line icing

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I just had my heater core,ac evap,and dash top replaced. My old ac evap was leaking so that was the main reason for all the work. Before ac work my center vent air temp would get about 33-34 degrees. My temps now after the work is with fan on high and outside temp at 92* the center vent will not get lower than 47-48*. With fan on low it gets up to 50*. The ac doesnt cycle alot like when it was low on 134a but the low side line going to compressor is iced up with all fan speeds but high. I checked low side pressure and it runs around 25 psi with fan on medium and it will have ice all the way to compressor with center vent temps at 47*. What if any problems does this look like? Thanks so much...

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Time to get out the manifold gauges and check the pressures. I hate to say it but low freon will causing icing problem because lower the pressure colder it gets typically. This also could be a low side switch problem that is not cutting out the compressor to allow for thawing too.

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Ok I did pressure checks.....90* Outside temp. Low side 32-34 psi high side 190 psi fan on high center vent temp at 51* with passanger side window down. Like I said with fan on high I dont get icing but lower fan speeds I get icing all the way to compressor. Is this normal?

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Yeap your low on freon... As the pressure starts to drop a bit the temp of the evaporator falls more and with high humidity the icing starts forming and no its not normal you want it to sweat but not ice up on you. Because after a while the evaporator will freeze solid and not pass air. So as you increase pressure slightly to about 40-45 PSI on the low side it will stop icing up. Typically the low side switch should shut down the compressor for freezing conditions.

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post-11155-138698178828_thumb.jpgOk I had to stop adding freon I had noo difference. It will start icing up at about 22psi and cycle off at 18psi. The gauge picture is with engine at 1500 rpm's right before it cycles off. Keep in mind I never lose any air flow I just have this icing. It cylces off thaws cycles back on and repeats. I did not have this before evap work and center vent would get 33-34* now just 47* is as low as it will go. Also understand it cools well but I know something is different than before. post-11155-13869817882_thumb.jpg

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Look at the scale for R134a and you'll see its 19-20*F temperature... Too cold.. Now look at your gauges... (Opps the red text should be lower 35*F and upper 40*F) :doh:post-2-138698178835_thumb.jpg Here is Dodge FSM suggested pressures... post-2-138698178844_thumb.png More freon the warmer its gets. As you see on the gauge as the pressure rises the temperature rises. When I was doing R12 A/C units they where charger to 40-60 PSI running. Then when I did fridgerators they where 2-5 PSI running. Take another look at the temp scale on your gauge and you'll see you need to add more freon yet.

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Thanks so much for the help! Help me understand something. If the system is properly charged and you are running the ac on a lower fan speed with windows up and the cabin air is getting cooler and the low side pressure will be dropping. Once the pressure gets to low 20's with a proper charge it shouldnt ice up right? The reason I ask is because even with old evap with it cycling of and on like normal I never seen icing on low side. I may need to get help at a shop. A little back ground with the work that was done.....I spent 900 bucks getting all the work done to find out what a crappy job they had done a few days later. My ac would totally freeze up after a few hours of running so I did alittle looking and found green dye leaking from my low pressure switch. I tried to unscrew it to find out why it was leaking but everytime it got close to coming off freon would pour out. Once it does that I knew I was screwed so I just unscrewed it and within a few mins it was totally gone. I could see that the little scraider valve was smashed down and the oring was torn so when the switch was removed the freon would just come out. I replaced scraider valve and oring around drier and screwed switch back on so that fixed my leak there. I recharged with 3 cans of refrigerant which is little over 2 lbs. I have noticed this low side icing since last year when I done this. I dont drive this truck that much and decided to figure this out. Now today I have added another 6 oz's. I know this may require a professional at this point but I want to thank you again with being patient with a AC newbie. Any other advice that you have I am all ears!

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Apparently you still have a slow leak somewhere... Because the the only time I've seen 20 PSI on the low side while recharging was at 45*F outside temp. The other fact is it odd that the low side switch is allowing the freezing to occur that switch shouldn't alway the compressor to run below 30 PSI it should be cycling right now.. But all the dodge Trucks I've down typically will have 35-45 PSI on the low side and about 35-45*F out of the center vent.

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Thanks so much for the help! Help me understand something. If the system is properly charged and you are running the ac on a lower fan speed with windows up and the cabin air is getting cooler and the low side pressure will be dropping. Once the pressure gets to low 20's with a proper charge it shouldnt ice up right? The reason I ask is because even with old evap with it cycling of and on like normal I never seen icing on low side. I may need to get help at a shop. A little back ground with the work that was done.....I spent 900 bucks getting all the work done to find out what a crappy job they had done a few days later. My ac would totally freeze up after a few hours of running so I did alittle looking and found green dye leaking from my low pressure switch. I tried to unscrew it to find out why it was leaking but everytime it got close to coming off freon would pour out. Once it does that I knew I was screwed so I just unscrewed it and within a few mins it was totally gone. I could see that the little scraider valve was smashed down and the oring was torn so when the switch was removed the freon would just come out. I replaced scraider valve and oring around drier and screwed switch back on so that fixed my leak there. I recharged with 3 cans of refrigerant which is little over 2 lbs. I have noticed this low side icing since last year when I done this. I dont drive this truck that much and decided to figure this out. Now today I have added another 6 oz's. I know this may require a professional at this point but I want to thank you again with being patient with a AC newbie. Any other advice that you have I am all ears!

did you evacuate the system to -20psi of pressure before charging? if not then it sounds like that is your culprit.

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Well a update.....I had another shop look at it. We had to replace the drier and I had to have the dash taken back apart to fix where the evap and heater core lines run through fire wall. The other shop did not seal up the holes where they run through it. I was losing tons of air flow out of them so I figured poor air flow was the reason for the suction line frosting. After all the work I have proper air flow out of vents and my temps are now 35-36* again.. But....I am still having frosting issues with suction line when fan speeds are on low.The shop pull a vac to verify I didnt have a leak and to remove any water. The refrigerant was measured in at 2lbs. The evap is not icing up to lose any air flow and the temps are great now but still seeing frosting on suction line to compressor. I am really confussed and I am about ready to forget about it because it is now working like it did when the truck was new. I have spent $1900 so far had 2 driers replaced and dash removed twice. LOL any other ideas I am all ears! Thanks for everyones help!

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My name is Layman :lmao: This is what I have done to get 29 degree. Make sure you have a new orfice line because they will get restricted. Let all freon out (have somebody suck it out) vacuum the system down,Get two cans = 2lbs have a pan of hot water ready, roll all windows up and put on max high, put the first can in. Now use the hot water to get the AC to suck all freon in from second can. Dont get any liquid from the can in the system you could damage the compressor you just wont vapor. If it wont take it in the hot water will warm it up and let it do its thing.I dont know high sides and low all I know is if the compressor is new and the rest is in right order you will have 29 degree in the Texas hot weather of 113 :mad: I have done this three times and got the same result every time.

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