Pressures, Checking
-- Turn off the ignition.
-- Connect the A/C Service Station. Refer to A/C Service Station, CONNECTING .
-- Take pressure gauge readings (two possible results).
| Ambient Temperature in °C (°F) | Pressure in Refrigerant Circuit in bar (psi) Positive Pressure |
|---|---|
| 15 (59) | 3.9 (56.57) |
| 20 (68) | 4.7 (68.17) |
| 25 (77) | 5.6 (81.22) |
| 30 (86) | 6.7 (97.18) |
| 35 (95) | 7.8 (113.13) |
| 40 (104) | 9.1 (131.98) |
| 45 (113) | 10.5 (152.28) |
Temperature of refrigerant circuit components should be equal to ambient temperature.
Pressure will deviate from values in table if individual components of refrigerant circuit are warmer or colder.
At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure (positive pressure) corresponds to 1 bar (14.5 psi) absolute pressure. 0 pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated by -1 bar (14.5 psi) below 0).
On vehicles with High Pressure Sensor -G65- with which the measured pressure is displayed in the measured value block, the measured pressure should correspond to the values in the table.
Refer to REFRIGERANT CIRCUIT .
The Refrigerant Circuit Pressure is Lower than Indicated in Table
Not enough refrigerant in refrigerant circuit
-- Determine refrigerant circuit leaks. Refer to REFRIGERANT CIRCUIT, TRACING LEAKS, WITH Electronic Leak Detector .
-- Check the pressure relief valve.
If pressure relief valve has responded:
-- Check the coolant fan activation.
-- Check refrigerant lines and hoses for cross-section constrictions caused by inadequate bending radii.
-- Check refrigerant pipes and hoses for external damage.
-- If no malfunction is found, flush refrigerant circuit with compressed air and nitrogen.
The Refrigerant Circuit Pressure Is in Line with Table or Is Higher
-- Start the engine.
-- For vehicles with an electrically-driven A/C compressor, switch on the ignition.
High voltage is extremely dangerous.
The high-voltage system is under high voltage. Electrocution can cause death or very serious personal injury from damaged high-voltage components and high-voltage cables.
If procedures are necessary near the components of the high-voltage system, visually inspect the high-voltage components and lines for damage. Refer to HIGH VOLTAGE SYSTEM GENERAL WARNINGS
If it is necessary to perform work on the high-voltage system components, de-energize the high-voltage system (refer to DISABLING THE HIGH VOLTAGE SYSTEM ) and observe the "High-Voltage System General Warnings" (refer to HIGH VOLTAGE SYSTEM GENERAL WARNINGS ).
-- Set the A/C system to maximum cooling output.
If the low pressure switch was removed to connect the A/C Service Station, bridge the electrical connections in the corresponding connector for the pressure measurement.
- A/C compressor is driven by the engine via A/C Clutch -N25-.
- The A/C Compressor Regulator Valve -N280- is activated by the Climatronic Control Module -J255-.
Refer to the appropriate service information .
If A/C Compressor Is Not Driven with the Engine Running or Regulating Valve Is Not Actuated:
-- Determine and eliminate cause e.g. by checking air conditioner DTC memory.
-- Observe test conditions.
-- Check the A/C Clutch -N25- voltage supply. If it is OK, repair the A/C clutch.
-- Check activation of A/C Compressor Regulator Valve -N280-.
Refer to the appropriate service information .