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A/C gauges are reading retard on low side and 250 on high side?

Tiny
CWILSON25
  • MEMBER
  • 1998 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
A/C is blowing cold, but gauges are reading retard on low side and 250 on high side. Also, the compressor isn’t cycling.
Saturday, June 3rd, 2023 AT 11:43 AM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

What is the actual reading on the low side? Are you saying it is negative pressure?

Let me know.

Joe
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Saturday, June 3rd, 2023 AT 10:44 PM
Tiny
CWILSON25
  • MEMBER
  • 7 POSTS
No low side pressure was maxed as far as the manifold guard could read.
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Sunday, June 4th, 2023 AT 8:05 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Can you upload an image of the gauge pressure while running?
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Monday, June 5th, 2023 AT 8:18 PM
Tiny
CWILSON25
  • MEMBER
  • 7 POSTS
Sorry for the late response. I vacuumed down the system today and changed the orifice tube in truck. I added freon with 3 ounces of 150 pag oil in a can to equal a total of 2.25 pounds of Freon and oil together. Gauges read 50 PSI on the low side and 275 on high side. Ac was blowing extremely cold, but the compressor never cycled. It was only cycling as I added Freon. When I had almost a pound of Freon in the truck it stopped cycling and stayed engaged. It would stay engaged until I manually made it disengage.
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Saturday, June 10th, 2023 AT 12:52 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

First, what were the outside temperatures when you checked pressures? The readings you have sound good, but I just want to confirm they are within range for the temperature.

Next, when the A/C is on low, see if it cycles. Note: It may take longer to cycle based on temperature. The high-pressure switch is designed to turn it off if there is an issue.

Let me know. Also, I'm glad you got it working properly.

Joe
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Saturday, June 10th, 2023 AT 8:09 PM
Tiny
CWILSON25
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  • 7 POSTS
The outside temperature was 90 degrees feel like temperature was 102 degrees. It’s blowing cold just will not cycle even when air is on low.
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Sunday, June 11th, 2023 AT 1:12 PM
Tiny
CWILSON25
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  • 7 POSTS
It started cycling on low this evening.
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Sunday, June 11th, 2023 AT 4:40 PM
Tiny
CWILSON25
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  • 7 POSTS
It started cycling on low this evening
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Sunday, June 11th, 2023 AT 4:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

Thanks for the update. Based on the temperatures you are in; it sounds like it is working correctly. Also, I assume when it started cycling, the temperature was cooler.

Let me know if that is correct.

Take care,

Joe
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Sunday, June 11th, 2023 AT 5:18 PM
Tiny
CWILSON25
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Yes, I was holding the rpm’s around 2,200 2,500 RPMs and it would cycle on low. Still wouldn’t cycle when the blower was on high.
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Sunday, June 11th, 2023 AT 7:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
The only other thing I can think of that would prevent it from cycling is if it is a charging issue. What are the high and low pressure readings and the outside temperature when checked?

Please keep in mind, what you are experiencing is not abnormal. When you request max A/C, if the temperature is high enough, it won't cycle.

Joe
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Monday, June 12th, 2023 AT 8:04 PM

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