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2004 Tahoe A/C high/low pressures

Discussion in 'Interior' started by ueww40, Jun 28, 2020.

  1. ueww40

    ueww40 TYF Newbie

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    Aug 5, 2017
    The other day I went out and got myself a beautiful professional A/C manifold gauge set to check the status of the A/C system on my 2004 Tahoe. As far as the proper pressures of the system are concerned the instructions on how to use the set say to follow the manufacturer's recommendations. I am confused now. I always thought that all automotive A/C systems operate within the same perimeters. A fully charged, properly working A/C system should be around 50 psi on the low side and around 250 psi on the high side +/- allowances for ambient outside temps. Is that correct? Or are these specs different for my Tahoe which has front and rear separately controlled A/C. The reading I got on my Tahoe was 60 psi on the low side and 265 psi on the high side at an outside temp of 87 F. Is that a good reading?
  2. PNWTahoe

    PNWTahoe Full Access Member

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    May 13, 2015
    Olympia, WA
    Ta Hoe
    A/C Refrigerant Pressure Sensor
    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 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).

    A/C Low Pressure Switch
    The A/C low pressure switch protects the A/C system from a low pressure condition that could damage the A/C compressor or cause evaporator icing. The HVAC control module applies 5 volts to the A/C low pressure switch signal circuit. The switch will open when the A/C low side pressure reaches 151 kPa (22 psi) . This prevents the A/C compressor from operating. The switch will then close when A/C low pressure side reaches 275 kPa (40 psi) . This enables the A/C compressor to turn back ON.
    PNW VietVet likes this.
  3. PNW VietVet

    PNW VietVet Supporting Member

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    Oct 8, 2014
    Humidity will/can make a difference as well. What was the temp at the front dash center vent? Temp on high fan? Temp on low fan?

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