A/C compressor runs constantly?

Tiny
JKRO1098
  • MEMBER
  • 2007 CHEVROLET 2500
  • 6.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 382,000 MILES
I recently did some work on my A/C system. The old compressor failed and there was a leak in the system, so I changed most of the old components. I got a new compressor, new condenser, new accumulator/receiver drier and a new aluminum line from the condenser to the evap core with a new orifice. I flushed the old lines and the evap core with A/C solvent and blew them out dry with dried compressed air. The new compressor came prefilled with 8oz of pag 46 oil. I pulled a vacuum on the system and then began to charge it. I got one 12oz can in and then started to fill another can when the high side discharge line from the compressor to the condenser blew. Before it blew, the compressor clutch was cycling rather quickly, like a second on then off, I thought that was a bit abnormal. I replaced the discharge line, dumped maybe a 1/2oz of pag 46 in the discharge side of the compressor. Then I pulled a vacuum, added some dye in the yellow charge line then charged it once again. I purged the yellow charge line of air both times (before the line blew and the second time before charging). I charged with two 12oz cans and then noticed that the compressor was running constantly. I'll add a picture of the pressures on the gauges after I stopped adding refrigerant. Then I replaced the cycling switch on the accumulator/receiver drier. The compressor still ran constantly. So, then I replaced the high side sensor switch on the discharge line, again compressor still ran constantly. I pulled the A/C Comp fuse and the compressor clutch kicked off, so I know it's not a mechanical issue with the compressor, but now I'm stumped.
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Monday, July 8th, 2024 AT 7:39 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,506 POSTS
So, when you say it blew the line what happens, did it come disconnected? What was the high side pressure at the time, also I would remove the orifice tube to make sure it is not clogged with debris. The pressures on the gauge in the image you have provided looks okay. Also, was the A/C cold at any time during this operation? Can you please give me the outside temperature where you are at? Please give me more information so I can help you.
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Monday, July 8th, 2024 AT 11:36 AM
Tiny
JKRO1098
  • MEMBER
  • 13 POSTS
Of course, so what I mean by the line blew, The discharge hose from compressor to condenser has a rubber hose section in the middle and it blew a hole in the rubber section. That line hasn't been changed the entire life of the vehicle so I thought it was just old and worn.

The temperature was into the 100's while I was doing this.

Unfortunately, at that time, the high side gauge wasn't showing any pressure so I don't know what it was when it blew. I was getting cold air before it blew. At the time it did blow, I had barely charged a small amount from the second can of refrigerant.

It wasn't till the second time I charged the system that the low side was reading 30psi that I stopped charging. I decided I really needed to see the high side pressure before adding more. I closed the low side blue knob on the manifold and unscrewed the red hose to the manifold just a little bit, pressure spewed out, the gauge started showing pressure, then I screwed the red hose back in to stop the spewing. Apparently you can tighten the hose to the manifold too much and the gauge wont read. At this point the low side read 30 psi, the high side read 200 psi. I added a little more refrigerant till the gauges read what they do in the picture and stopped. The AC was nice and cold, but the compressor still ran constantly.

Lets back up to the first time I charged the system and the discharge line blew. After it blew, I did take out the orifice. There was a little debris on it, but not enough to clog the system. I took the line off the condenser to the orifice, with the orifice out, and shot compressed air through it. I thought maybe the condenser might be clogged, so with both lines off of it, I shot compressed air through it the opposite way and didn't notice any constriction. My compressed air is dried by the way. I cleaned the orifice off, installed it and then installed the line to the condenser. Before I installed the new discharge hose, I thought maybe I lost a little oil when it blew, so it was at this time I added the 1/2oz of oil in the discharge port of the compressor, installed the new line, and continued with the next steps of charging the system the second time.
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Tuesday, July 9th, 2024 AT 8:17 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,506 POSTS
It sounds like you may have too much oil in the system, also the gauge set may not be working correctly, giving you false pressure readings. Here is a video you can go over to get a quick update on pressures and how to charge the system, you should never open the high side (Red) valve.

https://youtu.be/4EqdrBVb0sY?si=W3vPy4PbbNJwT3cm

When the system is fully charged the A/C compressor will not cycle, it will stay on while the system is running.
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Tuesday, July 9th, 2024 AT 9:55 AM

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