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Home >> Audi >> 2016 >> S5 Prestige, 2D Convertible >> Repair and Diagnosis >> External Pages >> Different car >> Section 1499 (Heating & Air Conditioning (On Board Diagnostic)) >> 01 On Board Diagnostic (OBD) >> Read Measuring Value Block (function 08) >> Measuring value blocks from "001" to "010" >> Display group "001"

Display group "001"

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A/C Compressor Regulator Valve N280 and High Pressure Sensor G65 

NOTE:
  • In the event of a compressor shutoff condition, the A/C Compressor Regulator Valve N280 cannot be activated even during Output Diagnostic Test Mode (DTM) diagnosis (→ Output Diagnostic Test Mode (DTM) (function 03) ).
  • If no pressure signal from the High Pressure Sensor G65 is detected, the A/C Compressor Regulator Valve N280 must not be activated.
Display field Meaning Remarks
1 Measured control current for A/C Compressor Regulator Valve N280 (in amps)
  • Current flowing via A/C Compressor Regulator Valve N280
 
  • Display = less than 0.050 A
  • Compressor switched off
  
 
  • Display = 0.300 A to 0.650 A (up to 0.8 A)
  • Compressor in control mode; control current is governed by cooling output required
  
NOTE:
  • Display field "1" indicates the current flowing via the A/C Compressor Regulator Valve N280.
  • The current is calculated by the operating and display module, Climatronic Control Module J255 and is governed by the required cooling output, the operating mode selected (set) for the operating and display module, Climatronic Control Module J255 and the electrical system voltage. The regulating valve can however only operate reliably if there is a specified minimum current flow (0.3 A for the regulating valves installed at present).
  • Full A/C Compressor Regulator Valve N280 activation results in a maximum current of at present approx. 0.65 A (up to 0.8 A) depending on vehicle electrical system voltage and the version of the operating and display module, Climatronic Control Module J255 (calculated, regulated and limited by operating and display module, Climatronic Control Module J255).
  • If the pressure in the refrigerant circuit (display zones "3" and "4") does not change when the engine is running despite the A/C Compressor Regulator Valve N280 being activated with maximum current, check the pulley or the drive unit at the compressor. The compressor must be driven (if the overload safeguard has been triggered, the pulley turns, for example, but the compressor is not driven) → Belt pulley/drive unit of compressor, replacing .
Display field Meaning Remarks
2 Duty cycle for activation of A/C Compressor Regulator Valve N280 (in %)
  • Time component of A/C Compressor Regulator Valve N280 activation
 
  • Display = 0%
  • Compressor switched off
  
 
  • Display = 30 to 40% to 100%
  • Compressor in control mode, activation time is governed by cooling output required, operating mode selected and electrical system voltage. The minimum activation time is however that required to achieve a mean current flow of 0.3 A and the maximum time is such that a mean current of 0.65 A (0.8 A) is not exceeded.
  
NOTE:
  • The duty cycle for the period during which current can actually flow is indicated in display zone "2".
  • The operating and display module, Climatronic Control Module J255 employs a frequency of 500 Hz (500 Hertz = 500 activation pulses per second). The duty cycle indicates the proportion of the ON time per pulse.
  • The activation signal can be checked for example using the Diagnostic Operation System VAS 5051A ("Measurement" function).
  • The duty cycle is selected by the operating and display module, Climatronic Control Module J255 such that the Evaporator Vent Temperature Sensor G263 attains the specified evaporator temperature, which is influenced by various factors.
  • If a malfunction is detected at the Evaporator Vent Temperature Sensor G263, the operating and display module, Climatronic Control Module J255 switches to emergency operation and the A/C Compressor Regulator Valve N280 is then only activated with a maximum control current specified by the software of the operating and display module, Climatronic Control Module J255. The maximum control current is governed by the version of the operating and display module, Climatronic Control Module J255 and may be between approx. 0.3 A and 0.5 A for the operating and display modules, Climatronic Control Module J255 installed at present (the cooling output of the air conditioner is thus reduced and the cooling effect is no longer sufficient at higher temperatures).
Display field Meaning Remarks
3 Ratio for pressure signal from High Pressure Sensor G65 (in %)
  • Time component of positive signal from High Pressure Sensor G65
 
  • Display = 0 to 5%
  • Open circuit in wiring between High Pressure Sensor G65 and operating and display module, Climatronic Control Module J255
  • Open circuit in power supply or Ground (GND) connection to High Pressure Sensor G65
  • High Pressure Sensor G65 defective
  
 
  • Display = 5% to 12 %
  • Insufficient pressure in refrigerant circuit (system empty)
  • High Pressure Sensor G65 defective
  
 
  • Display = 12 % to 87.5%
  • Pressure in refrigerant circuit in permissible range
  • If a ratio of less than 16.5 % is displayed at an ambient temperature above 20 °C, the measured value of the High Pressure Sensor G65 is not OK or there is not enough refrigerant in the circuit
 
  • Display = greater than 87.5 to 90%
  • Pressure in refrigerant circuit too high
  • Activation for Coolant Fan V7 not OK
  • High Pressure Sensor G65 defective
  • Radiator and/or condenser contaminated
  • Malfunction in refrigerant circuit
  
 
  • Display = 90 to 100%
  • Short to positive (or Ground (GND)) in wiring between High Pressure Sensor G65 and operating and display module, Climatronic Control Module J255
  • Open circuit in power supply or Ground (GND) connection to High Pressure Sensor G65
  • High Pressure Sensor G65 defective
  
NOTE:
  • The ratio for the period during which the signal is actually applied is indicated in display zone "3".
  • The operating and display module, Climatronic Control Module J255 uses the ratio to calculate the pressure in the refrigerant circuit. The calculated pressure is indicated in display zone "4".
  • If the ratio is less than 12 % (corresponding to approx. 1.8 bar absolute pressure) and greater than 87.5% (corresponding to approx. 32 bar absolute pressure), the operating and display module, Climatronic Control Module J255 does not switch on the compressor (the A/C Compressor Regulator Valve N280 is not activated). The compressor is only re-activated once the ratio exceeds 15 % (corresponding to absolute pressure of 2.6 bar) or drops below 48% (corresponding to absolute pressure of 16 bar).
  • To prevent abrupt compressor shutoff because of excessive pressure in the refrigerant circuit or excessive coolant temperature, the compressor output is reduced by the operating and display module, Climatronic Control Module J255 :
  • - As soon as the pressure in the refrigerant circuit exceeds 30 bar (absolute) (full compressor output is not released again until pressure has dropped below 16 bar)
  • - As soon as the coolant temperature exceeds 115 °C (full shutdown at 118 °C)
  • Depending on the ratio, the operating and display module, Climatronic Control Module J255 transmits a signal via the CAN-Bus comfort system to the relevant engine control module, thus causing it to act on the Coolant Fan Control (FC)Control Module J293 to switch the Coolant Fan V7.
  • At absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure thus corresponds to roughly 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (can be seen from "-1" mark below "0").
  • The pressure in the refrigerant circuit and thus the ratio are governed by various factors. As a general rule, however, the pressure will not exceed 20 bar (absolute) with maximum compressor output and an ambient temperature of 20 to 25 °C. Under extreme usage conditions (e.g. in hot countries with high ambient temperatures, "stop and go traffic" and high relative humidity), the extremely high cooling output involved may also result in pressures of up to 30 bar (absolute).
  • The High Pressure Sensor G65 operates with a frequency of 50 Hz (50 Hertz = 50 activation pulses per second). The signal ratio indicates the proportion of the ON time per pulse.
  • The activation signal can be checked for example using the Diagnostic Operation System VAS 5051A ("Measurement" function) (Checking signal from High Pressure Sensor G65).
  • The signal generated by the High Pressure Sensor G65 is also used to control the engine (the torque required to drive the compressor is governed by the pressure in the refrigerant circuit). Depending on the engine control module version, the signal is displayed as signal ratio in the measuring value block of the relevant engine control module.
  • The signal transmitted at a refrigerant circuit pressure of approx. 5 to 6 bar absolute corresponds to a signal ratio of approx. 22%, which is achieved with the compressor not running, at an ambient temperature of 20 °C and with the refrigerant circuit properly charged.
Display field Meaning Remarks
4 Pressure in refrigerant circuit (in bar absolute)
  • Display = less than 2.6 bar
  • Insufficient pressure in refrigerant circuit (system empty)
  • High Pressure Sensor G65 defective
  • The pressure is calculated via the signal ratio indicated in display zone "3" by the operating and display module, Climatronic Control Module J255.
 
  • Display = 2.6 bar to 29 bar
  • Pressure in refrigerant circuit in permissible range
  • If a pressure of less than 4 bar is displayed at an ambient temperature above 20 °C, the measured value of the High Pressure Sensor G65 is not OK or there is not enough refrigerant in the circuit
 
  • Display = greater than 29 bar (also for brief periods)
  • Pressure in refrigerant circuit too high
  • Activation for Coolant Fan V7 not OK
  • High Pressure Sensor G65 defective
  • Radiator and/or condenser contaminated
  • Malfunction in refrigerant circuit
  
NOTE:
  • Also observe the notes on display zone "3".
  • By way of the signal ration (display zone "3"), the operating and display module, Climatronic Control Module J255 calculates the pressure in the refrigerant circuit.
  • If the refrigerant circuit has been properly charged, the pressure settles at 2.6 bar at a temperature of -3 °C. To avoid a fault being stored at low temperatures, the operating and display module, Climatronic Control Module J255 only recognizes a fault in the refrigerant circuit at pressures of less than 1.8 bar (attained at -12 °C). The High Pressure Sensor G65 is however no longer checked at this temperature.
  • If the pressure in the refrigerant circuit (display zones "3" and "4") does not change when the engine is running despite the A/C Compressor Regulator Valve N280 being activated with maximum current, check the pulley or the drive unit at the compressor. The compressor must be driven (if the overload safeguard has been triggered, the pulley turns, for example, but the compressor is not driven) → Belt pulley/drive unit of compressor, replacing .
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