AC Clutch staying engaged all the time

Tiny
KENNY SMITH2
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 230,000 MILES
System had bad tensioner and replaced and put new belt on as belt wasn’t present when vehicle was purchased.

Noticed the AC wasn’t cold. Checked pressure and AC clutch was kicking in and out but was full of air and very little Freon. Evacuated system and installed can of oil and filled with Freon.

AC is very cold now but clutch will not disengage.

Any suggestions?
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Monday, June 10th, 2019 AT 4:50 PM

14 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome to 2CarPros.

First, the power-train control module (PCM) or monitors the high side refrigerant pressure via a A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low the signal voltage is low. When pressure is too high the PCM will not allow the A/C compressor clutch to engage. If pressure is too low, I believe it will allow the compressor to not cycle.

Now, you recharged the system. Can you tell me what both the high and low side pressures are? Also, please include out side temps. I feel that either you are low on Freon or the high pressure switch may be bad,

Here are directions showing AC manifold gauges. I'm adding them in case you need them. I have no idea if this is how you did it or not.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Let me know.

Joe
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Monday, June 10th, 2019 AT 8:49 PM
Tiny
KENNY SMITH2
  • MEMBER
Hi Joe,

Thanks for the information. Actually I just let the air out and recharged only at the low side. That s the way I ve always done it and never had issue with most of the vehicles I ve owned. Air is very cold, I put right about three smalls cans of
Freon in it as it holds I think about 34oz. I am sure it s over charged a little right now too. I had it at a garage yesterday and they suggested it was the high pressure sensor but I ve had people tell me it was bad compressor that would cause that too. I will try and change the high pressure sensor first and see if that solves it.

Thanks again.
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Tuesday, June 11th, 2019 AT 4:15 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

You are very welcome. I just hope that it helps. Honestly, it sounds like the sensor is the issue and not telling the PCM when to cycle. That is my first suspect.

I don't know if you need them, but here are the directions for replacing one. The attached picture correlates with the directions.

___________________________________

AIR CONDITIONING (A/C) REFRIGERANT PRESSURE SENSOR REPLACEMENT

TOOLS REQUIRED
J 39400-A Halogen Leak Detector

REMOVAL PROCEDURE
1. Raise and support the vehicle. Refer to Vehicle Lifting.

Picture 1

2. Disconnect the electrical connector from the A/C high pressure recirculation switch.
3. Remove the A/C high pressure recirculation switch from the evaporator tube.

INSTALLATION PROCEDURE

NOTE: Refer to Fastener Notice in Service Precautions.

Also Picture 1
1. Install the A/C high pressure recirculation switch.

Tighten
Tighten the switch to 6 N.M (53 lb in).

2. Connect the electrical connector to the A/C high pressure recirculation switch.
3. Leak test the fittings of the components using the J 39400-A.
4. Lower the vehicle.

I hope this helps. Let me know the results.

Take care,
Joe
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Tuesday, June 11th, 2019 AT 8:46 PM
Tiny
KENNY SMITH2
  • MEMBER
Hi again, I ve not replaced any sensors yet but I ve took both out and cleaned and when I hook them back up, the clutch works as it should, but when the pressure rises it seems it doesn t kick back down. Could this actually be a condenser fan/ condenser blockage?

My father in law says my compressor is failing, he says it isn t pumping the pressure back down. I don t really understand all this other than what I ve been researching.

Had someone tell me it was an ambient sensor too. I m now having heat on driver side come out and cold come out on passenger when ac is on. Happens about a minute after it s been on.
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Thursday, June 13th, 2019 AT 5:55 PM
Tiny
KENNY SMITH2
  • MEMBER
Also had pressures checked yesterday with manifold gauges and the low side read about 45 to 60 and the high was 225 to 250 and it was about 75 degrees.
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Thursday, June 13th, 2019 AT 6:01 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

Both sides are too high for that temperature. You have too much Freon in the system. You need to remove some. Do that first. At 75 degrees, low side should be between 35 and 40 and the high side should be 150 and 170.

Once you get the low side between 35 and 40, if the high side is still tool high based on what I mentioned above, then there is a good chance the orifice is plugged. However, the high pressure switch should be cycling the compressor off even now.
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Thursday, June 13th, 2019 AT 8:00 PM
Tiny
KENNY SMITH2
  • MEMBER
I ve lost a lot of Freon. Due to pressure rising and blowing o rings. If I release some of the pressure it will work until it gradually builds more up. I m stopped up somewhere just not exactly. Probably going to replace that sensor and clean the system.
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Friday, June 14th, 2019 AT 2:42 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
If there is a plug, my first suspect would be the orifice tube. As far as the sensor, if it isn't too much money, just replace it.
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Friday, June 14th, 2019 AT 6:49 PM
Tiny
KENNY SMITH2
  • MEMBER
Would the A/C still be cold continuously?
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Sunday, June 16th, 2019 AT 10:35 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
One would think it wouldn't, but that is the most common place for a blockage.
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Sunday, June 16th, 2019 AT 8:38 PM
Tiny
KENNY SMITH2
  • MEMBER
What about condenser radiator? Would it be wise to check there as well? I have a new low pressure/cycling switch and a high pressure transducer switch on the way to replace and try first. Just really odd. I ve never see one still get cold and do that.

Can you explain to me what makes a compressor actually start the pump down cycle? Does it cycle up and then just kick off and release the low pressure on its own or what exactly?
Sorry for so many questions just trying to understand all the AC components and workings of the compressor itself.
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Sunday, June 16th, 2019 AT 8:46 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

Honestly, if you have any questions, never worry about asking. I'm glad there are people that are interested in learning. Here is what causes the system to cycle. This is a description of the high pressure switch and its purpose.

The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0.5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts. The powertrain control module (PCM) converts the voltage signal to a pressure value.

The A/C refrigerant pressure sensor protects the A/C system from operating when an excessively high pressure condition exists. The PCM disables the compressor clutch if the A/C pressure is more than 2957 kPa (429 psi). The clutch will be enabled after the pressure decreases to less than 1578 kPa (229 psi).

I hope that helps.

Take care,
Joe
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Sunday, June 16th, 2019 AT 8:57 PM
Tiny
KENNY SMITH2
  • MEMBER
How about the low pressure/cycling switch. Is that actually what signals the compressor to engage and disengage the clutch or does the compressor do that on its own?
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Monday, June 17th, 2019 AT 8:16 AM
Tiny
KEN
  • ADMIN
Yes, that is correct. You might have too much oil in the system causing the issues. But to be sure lets unplug the pressure sensor to see if the compressor clutch disengages. Here is the location. The pressure seem okay to me so I don't think the seals are gone. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Tuesday, June 18th, 2019 AT 12:22 PM

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