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Old 06-05-2018, 07:09 PM   #1
zedjr10
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AC issue. Compressor never cuts off. 0 high port pressure reading?

I just redid almost my entire ac system. Compressor, condenser, dryer, expansion valve, and system flush. After all done my ac works good it seems but compressor never cuts off and there is a 0 reading on high pressure port when i charged it for first time. What are my possibilities. Did i forget to pull a little black plug out of somewhere like the expansion valve. Is the valve just faulty? When i was evacuating the system i had a leak on high side i didn't realize until later. Could that cause this. DO i need to evacuate and recharge? That tutorial i tried to follow suggested a bad expansion valve but everywhere else i looked said that isn't possible to have 0 reading with ac working and bad valve. Anyone?
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Old 06-05-2018, 07:49 PM   #2
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Not to sound mean, bit you did open the valve on the high side line, right? Unless the system is empty or your guage is broken is the only way you could have a 0 reading. If it was a leak you would still see pressure, falling as it bleeds off. You would also smell it, and if the leak is large enough, you would hear it.
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Old 06-05-2018, 07:55 PM   #3
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Quote:
Originally Posted by Size9zombie View Post
Not to sound mean, bit you did open the valve on the high side line, right? Unless the system is empty or your guage is broken is the only way you could have a 0 reading. If it was a leak you would still see pressure, falling as it bleeds off. You would also smell it, and if the leak is large enough, you would hear it.
It is the fkn gauge. Thank god also. Just high fived my wife. So it works all ok i guess except compressor never cuts off. I just went out and checked again. This time testing the schrader valve itself. Plenty of pressure. THe thing on the manifold set doesn't reach down enough. I replaced the schrader valve first with same size one. WHich is also the same size as low side port. IS this normal. Now i need another gauge set with a needle that reaches farther as i went to evacuate and fill with proper amount. Is 120 in on low side ok when ac is off. Why the heck does compressor never cut off. I got the high side gauge to read 80 in but not sure if it is even accurate as needle is barely pressing on valve. I had to press on it with my hand to get that reading. What a pos gauge set or my valve isn't right size.

Last edited by zedjr10; 06-05-2018 at 08:20 PM.
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Old 06-05-2018, 08:11 PM   #4
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Was the valve open on the manifold gauge and closed on the end of the hose?

This is what Size9Zombie was asking. If the valve on the manifold is closed you will get a 0 reading forever. Also not having the system in vacuum prior to charging the system is reducing it's ability to cool. Any moisture and or oxygen is reducing the effectiveness of the R134a.
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Old 06-05-2018, 09:16 PM   #5
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Originally Posted by Rilas View Post
Was the valve open on the manifold gauge and closed on the end of the hose?

This is what Size9Zombie was asking. If the valve on the manifold is closed you will get a 0 reading forever. Also not having the system in vacuum prior to charging the system is reducing it's ability to cool. Any moisture and or oxygen is reducing the effectiveness of the R134a.
Yeah all the compressed air now in there. I plan on getting another gauge set and re-evacuating and charging. Maybe this is why compressor stays on all the time. I hope so. Why does the valve sit lower than low side port. I mean the reason the needle doesn't reach it is cause it sits a little lower. I hope the next gauge set needle is deeper. Is there a way to fix this schrader valve or is it the way it is supposed to be.
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Old 06-05-2018, 11:11 PM   #6
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Yes it is normal for the schrader valves to be the same, different size ports, small is low side bigger of the 2 is high side. Static pressure of the system will fluctuate with ambient temprature, but 100 to 120 is normal when the a/c is off. The compressor can and will run all the time as long as the high side pressure doesn't reach a predetermined pressure at which point it will cycle off until the pressure drops to a certain point, then it will turn back on. As we said, before you charge it, MAKE SURE it is vaccumed to atleast 30 inHg, for at LEAST 30 mins. If it doeant gwt all the way to 30 inHg of vaccum AND HOLD IT FOR AT LEAST 5 MINS, then there is still a leak somewhere that needs to be addressed BEFORE you charge the system with refrigerant. The gauge you have on the high side is wrong. High side pressure goes up. If the low side gauge was showing 120 static then it would be 220 or better while running. The low side should be 30iah depending on how hot ambient temp is when you are looking at it.

Last edited by Size9zombie; 06-05-2018 at 11:15 PM.
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Old 06-06-2018, 02:49 AM   #7
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Fixed the schrader valve. Evacuated and charge. Works perfect. Compressor stays on longer than before i think but it does cycle off and on and high side and low side pressures look good. So all good to go. Was soo glad it was a stupid schrader valve not tightened down.
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Old 06-06-2018, 09:30 AM   #8
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Good job, glad you got it done.
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Old 06-06-2018, 11:45 AM   #9
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Nice. Sorry I havenít been on, long days recently.
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Old 06-07-2018, 02:31 AM   #10
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Quote:
Originally Posted by Size9zombie View Post
Good job, glad you got it done.
I think i effd something up in an attempt to get my compressor to cycle right. Am so depressed now. I made a new post about it. Have to take the manifold gauge back also as it sprang a leak. Hopefully the lines just froze up temporarily and didn't mess anything up in the system.
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Old 06-07-2018, 09:19 PM   #11
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My gauge set was defective. Lesson to anyone doing this. CHeck and make sure your manifold gauges work and are assembled right and tight. The first set i get from autozone the high side leaked and it blew a line. Not to mention i had to tighten it really tight. THe second set had different problems. THe vacuum line only flowed one way so i had to switch it back when charging it. And if i tightened it too tight it would not work at all. The easy way to check is to connect it to your ports. Open the port valve and then look at your reading. Now close the port valve and disconnect it from low side. Once disconnected open it back up and see if it goes to 0. You may need to open the valve on manifold gauge to go to 0. Then close it. After that reconnect to low side and open the port valve and see if you get your reading from low side port. It should've been the same as when you had it connected before.THe high side you check the same way. You will save yourself the trouble of many hours assuming the gauges work. As both sets i got had problems.
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