Heating and A/C System Changes, 1997 >

Heating And A/C System Changes, 1997 >

On Board Diagnostic changes
- New A/C control head -E87- with specific coding for m.y. 1997, 4-cyl. and 6-cyl. engines.

NOTE:
- Before performing On Board Diagnostic of A/C system, ensure A/C control head -E87- is coded correctly (according to engine application).
- A/C control heads beginning with Part No. 8L0 820 043 should only be installed in m.y. 1997 vehicles.
- A/C control heads beginning with Part No. 8D0 820 043 must only be installed in vehicles through m.y. 1996.

CAUTION:
- Part numbers are for reference only.
- Always check with your Parts Dept. for the latest information.

NOTE:
- For m.y. 1997, changes that affect monitoring of the A/C system by A/C control head - E87- were made.
- Monitored components, locations.
- Additional technical data and notes.
- If a replacement A/C control head is not coded after installation or if an unrecognized code was entered, code "04142" (Audi A4 -4cyl. -USA) is stored.
- The A/C control head is no longer connected to terminal 30 (vehicle electronics). The last input setting (into the A/C control head) is stored when the ignition is switched off and retained when the ignition is switched on.
- The duration of time when ignition is off is calculated by the A/C control head. When ignition is switched on, the previous "standing time" is calculated by monitoring a time signal from the instrument cluster. If more than 4 hours pass since ignition was switched off, the actual measured values of the outside temperature sensor are used as instantaneous outside and engine temperature inputs for A/C system control. If "standing time" is shorter than 4 hours, the actual measured values of the outside temperature sensor are suppressed and system output temperature control is calculated by the A/C control head. The "standing time" period is monitored and used for this calculation. (Heat radiating from the engine and radiator leads affects the measured value of the temperature sensor).

The following components previously monitored by OBD and triggered by A/C control head -E87- are deleted:
- Refrigerant low pressure switch -F73-.
- Refrigerant high pressure switch -F118- (low and high pressure switch functions integrated into A/C pressure switch, -F29-).
- Fresh air/recirculating flap two-way valve -N63-.

The following new components are monitored by OBD and provide input signals to -E87-:
- A/C pressure switch -F129-.
- Sender for outlet temperature, center -G191-.
- Sender for outlet temperature, floor outlet -G192-.

The following components monitored by OBD or triggered by -E87- are revised:
- The heater/air conditioner assembly with all servo motors.
- The fresh air blower and control module.

Following components that provide input signals to the A/C control head -E87- are revised:
- Instrument cluster

A/C system changes
- Revised heating/air conditioner assembly with flap motors.
- The air flow flap motor now activates the fresh air/recirculating air flap as well.
- The two way valve for the circulating/fresh air door, the vacuum unit and the vacuum reservoir are deleted.

A/C refrigerant circuit changes
- New service valve connection on low pressure side.
- Service valve connection for high pressure side installed in high pressure line in plenum panel (deleted at condenser).
- A/C pressure switch -F129- replaces pressure switches -F73- and -F118-.
- New version "Zexel" compressor and high pressure line (4-cyl. engines only).