Air conditioning is switched on by push button located to right of blower control knob. see scheme 1 A/C system will operate only at temperatures greater than 37°F (3°C) with engine on. At least one air outlet must be open when operating A/C system, to prevent evaporator freeze-up.
Air Distribution Control Knob
Rotary motion of control knob varies amount of air to defroster, footwell and instrument panel outlets. Defrost is controlled by temperature and blower controls. An illustration below temperature control knobs shows settings for maximum defrost.
Blower Control Knob
Blower control knob allows volume of air entering passenger compartment to be varied. Airflow increases as knob is turned clockwise. Airflow decreases automatically at speeds greater than 50 MPH. When A/C switch is turned on with blower control knob in "0" position, a small amount of air will continue to enter passenger compartment. Blower control knob has 5 positions, and allows 4 different blower motor speed settings.
Pushing recirculated air button cuts off outside air flow.
Temperature Control Knob
Temperature control knobs determine temperature of air entering driver-side or passenger-side compartment. Turning control knob clockwise will increase air temperature. Selected air temperature will stabilize within passenger compartment shortly thereafter.
Scheme 4
Condenser
Note. Use Pulley Holder (11 5 050 on 318 Series or 11 5 030 on 325 Series) to hold radiator (cooling) fan pulley. Turn 32-mm Wrench (11 5 040) clockwise to remove cooling fan. Cooling fan nut uses left-hand threads.
PIN VOLTAGE CHARTS
Pin voltage charts are supplied to reduce diagnostic time. Checking pin voltages at the A/C-heater control unit determines whether it is receiving and transmitting proper voltage signals. Charts may also help determine if A/C-heater control unit wiring harness has a short or open circuit.
Note. All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with minimum 10-megohm input impedance.
| Pin No. | Function/Description | Signal Type Or Voltage Value |
|---|---|---|
| 1 | A/C-Heater Control Panel Voltage | 12 Volts |
| 3 | Air Flow Control Knob | 0.6-4.0 Volts |
| 5 | A/C Push Button | Zero Volts (On); 10 Volts (Off) |
| 6 | A/C Indicator Light | 2.7 Volts (LED On/Lights Off); 8.9 Volts (LED Off/Lights Off) |
| 7 | Air Recirculation Button | Zero Volts (On); 10 Volts (Off) |
| 8 | Air Recirculation Indicator Light | 2.7 Volts (LED On/Lights Off); 8.9 Volts (LED Off/Lights Off) |
| 9 | Control Knob Lights | Ground Circuit |
| 10 | Indicator Lights Voltage Supply | 10 Volts (Lights Off) 4 Volts (Lights On/Indicator Light On) 6 Volts (Lights On/ Indicator Light Off) |
| 11 | Control Knob Lights & Indicator Lights | Voltage Input (Interior Lights) |
| 14 | Water Valves | 12 Volts |
| 15 | Interior Sensor Blower Activation | Zero Volts (Ignition On); (2) 12 Volts (Ignition Off) |
| 16 | Control Knob Reference Signal | 5 Volts |
| 17 | Control Knobs & Interior Temperature Sensor | Ground Circuit |
| 18 | Temperature Sensor (Left) | 0.5-4.2 Volts At 61-90°F (16-32°C) |
| 19 | Temperature Sensor (Right) | 0.5-4.2 Volts At 61-90°F (16-32°C) |
| 21 | Interior Temperature Sensor | 1.7-3.4 Volts At 50-104°F (10-40°C) |
| 22 | Ventilation Flap Switch | Zero Volts (On); 10 Volts (Off) |
| 23 | Rear Window Defogger Push Button | Zero Volts (On); 10 Volts (Off) |
| 24 | Rear Window Defogger Indicator Light | 2.7 Volts (LED On/Lights Off) |
| 25 | Push Buttons & Ventilation Flap Switch | Ground Circuit |
| (1) Pin assignments not listed are not used. (2) Reading is obtained after ignition is off for 3 minutes. | ||
| (1) | Pin assignments not listed are not used. |
| (2) | Reading is obtained after ignition is off for 3 minutes. |
A/C-HEATER CONTROL PANEL PIN ASSIGNMENTS (1)
| Pin No. | Function/Description | Signal Type Or Voltage Value |
|---|---|---|
| 1 | Terminal No. 50 | 12 Volts (When Starting) |
| 2 | Terminal No. 61 (Unloader Relay) | Zero Volts (Engine Off); 12 Volts (Engine Running) |
| 4 | A/C-Heater Control Unit Voltage | 12 Volts |
| 5 | Left Water Valve Activation | 0-100% (0-12 Volts) |
| 9 | Terminal No. 15 Independent Ventilation | 12 Volts |
| 12 | Right Water Valve Activation | 0-100% (0-12 Volts) |
| 14 15 | A/C-Heater Control Unit Power | 12 Volts |
| 16 17 | Load Circuit | Ground Circuit |
| 18 | (2) DME Activation (Anti-Stall) | Zero Volts (Off); 12 Volts (On) |
| 21 | Nominal Temperature Value (Right) | 0.5-4.2 Volts At 61-90°F (16-32°C) |
| 22 | Nominal Temperature Value (Left) | 0.5-4.2 Volts At 61-90°F (16-32°C) |
| 23 | Nominal Air Flow Value | 0.6-4.0 Volts |
| 24 | Interior Temperature Sensor | 1.7-3.4 Volts At 50-104°F (10-40°C) |
| 26 | Terminal No. 31 (Electronics) | Ground Circuit |
| (1) Digital Motor Electronics (DME). (2) Pin assignments not listed are not used. | ||
| (1) | Digital Motor Electronics (DME). |
| (2) | Pin assignments not listed are not used. |
A/C-HEATER CONTROL UNIT PIN ASSIGNMENT (BLACK CONNECTOR) (1)
| Pin No. | Function/Description | Signal Type Or Voltage Value |
|---|---|---|
| 1 | Air Recirculation Flap Motor Voltage | 11 Volts |
| 2 | Air Distribution Flap Motor Voltage | 11 Volts |
| 3 | Fresh Air Flap Motor Voltage | 11 Volts |
| 6/9 | Air Recirculation Flap Motor Activation | 0-100% (11 Volts When Motor Is Off) |
| 10-13 | Fresh Air Flap Motor Activation | 0-100% (11 Volts When Motor Is Off) |
| 14 | Control Knobs Reference Signal | 5 Volts |
| 15 | Diagnostic Initiation Line (RxD) | Input Signal |
| 16 | Diagnostic Data Line (TxD) | Output Signal |
| 17 | Ventilation Flap Switch | Zero Volts (On); 10 Volts (Off) |
| 18 | Interior Blower Sensor Activation | Zero Volts (Ignition On); (2) 10 Volts (Ignition Off) |
| 20 | Rear Window Defogger Activation | Zero Volts (On); 12 Volts (Off) |
| 22 | A/C Compressor Fan (Stage 1) | Zero Volts (On); 12 Volts (Off) |
| 23-26 | Mixing Flap Motor | 0-82% (Vent Flap Switch Off); 100% (Vent Flap Switch On) 11 Volts (Motor Off) |
| (1) Pin assignments not listed are not used. (2) Reading is obtained after ignition is off for 3 minutes. | ||
| (1) | Pin assignments not listed are not used. |
| (2) | Reading is obtained after ignition is off for 3 minutes. |
A/C-HEATER CONTROL UNIT PIN ASSIGNMENTS (BLUE CONNECTOR) (1)
| Pin No. | Function/Description | Signal Type Or Voltage Value |
|---|---|---|
| 1 | Air Recirculation Indicator Light | 2.7 Volts (LED On/Lights Off); 8.9 Volts (LED Off/Lights Off) |
| 3 | Rear Window Defogger Indicator Light | 2.7 Volts (LED On/Lights Off); 8.9 Volts (LED Off/Lights Off) |
| 4 | A/C Indicator Light | 2.7 Volts (LED On/Lights Off); 8.9 Volts (LED Off/Lights Off) |
| 5 | Rear Window Defogger Push Button | Zero Volts (On); 10 Volts (On) |
| 6 | Air Recirculation Push Button | Zero Volts (On); 10 Volts (On) |
| 7 | A/C Push Button | Zero Volts (On); 10 Volts (On) |
| 9 | Push Button, Vent Flap Switch & Indicator Lights | Ground Circuit |
| 10 | Air Distribution Control | Ground Circuit |
| 11 | Temperature Sensor | Ground Circuit |
| 12 | Control Knobs & Interior Temp. Sensor | Ground Circuit |
| 13 | Air Distribution Control Reference Signal | 4.7 Volts |
| 14 | Indicator Light Voltage Supply | 10 Volts (Lights Off) 4 Volts (Lights On/Indicator Light On) 6 Volts (Lights On/Indicator Light Off) |
| 15 | Terminal 58K | 12 Volts (Lights On) |
| 18 | Engine Speed Signal | Input Signal (Ignition On/Engine Off) |
| 19 | Road Speed Signal | Input Signal |
| 20 | Independent Ventilation | Zero Volts (On); 11 Volts (Off) |
| 21 | Nominal Mixing Value | 1.6-2.7 Volts; 0-100% |
| 22 | Evaporator Temperature Sensor | (2) 1.6-3.4 Volts At 25-79°F (-5-26°C) |
| 23 | Outside Temperature Sensor | (2) 0.6-4.5 Volts At -32-104°F (-40-40°C) |
| 24 | Left Heater Temperature Sensor | (2) 0.7-4.3 Volts At 32-194°F (0-90°C) |
| 25 | Right Heater Temperature Sensor | (2) 0.7-4.3 Volts At 32-194°F (0-90°C) |
| (1) Pin assignments not listed are not used. (2) Reading should be 5 volts with temperature sensor disconnected. | ||
| (1) | Pin assignments not listed are not used. |
| (2) | Reading should be 5 volts with temperature sensor disconnected. |
A/C-HEATER CONTROL UNIT PIN ASSIGNMENTS (WHITE CONNECTOR) (1)
