A/C blows warm, compressor engaged, pressure variable

Tiny
SWOFRA
  • MEMBER
  • 2005 ACURA TL
  • 74,009 MILES
When AC off/not selected, 134a pressure at low pressure port reads 55. When AC is selected I can hear it click on, hear a hiss inside the car, and visibly see the compressor clutch engaged continuously. 134a Pressure measures 0. Heat works, fan works. It has not been recently serviced. Any ideas? Thanks in advance.
Sunday, February 18th, 2018 AT 8:48 AM

6 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning.

When it is running can you give me the high and low side readings? Do you have a set of gauges? If not, you can rent a set at a parts store. Need those readings to see if the pressures are correct.

Roy
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Monday, April 26th, 2021 AT 10:46 AM
Tiny
SWOFRA
  • MEMBER
  • 4 POSTS
When gauges first hooked up and car has not started, low pressure reads 35 and high reads 50. After starting car with AC off, not difference. When AC turned on low immediately drops to zero and high is about 60-65. Compressor clutch is engaged continuously when AC on, even if set to max heat. When AC cycled off again, clutch stopped and low pressure rose to 45 and high pressure dropped to 50.
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Monday, April 26th, 2021 AT 10:46 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Okay.

From those readings, you need a expansion valve and dryer right off the battery. With the engine off, the pressures should be equal. At no time should the low pressure go to 0.

You will need an expansion valve and dryer, evacuate the system and charge with proper amount of Freon.

Roy
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Monday, April 26th, 2021 AT 10:46 AM
Tiny
SWOFRA
  • MEMBER
  • 4 POSTS
If I let it run for about five minutes with the A/C off, the low and high pressures are equal at about 40-45. Does that still mean I need the expansion valve and dryer?
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Monday, April 26th, 2021 AT 10:46 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
The unequal pressures at rest are the indicator as well as when you turn it on, the low pressure goes to 0.

Roy
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Monday, April 26th, 2021 AT 10:46 AM
Tiny
SWOFRA
  • MEMBER
  • 4 POSTS
Thanks, I installed a new expansion block fixed it!
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Monday, April 26th, 2021 AT 10:46 AM

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