Mercedes-Benz ML320. Manual — part 646

2001 Mercedes-Benz ML320

2000-01 MANUAL A/C-HEATER SYSTEMS ML 320, ML 430 & ML 55

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Fig. 2: Locating Climate Control Components
Courtesy of MERCEDES-BENZ OF NORTH AMERICA

FRESH/RECIRCULATION SWITCH

Fresh/recirculation switch controls voltage signal to fresh air recirculation door motor. See Fig. 1 and Fig. 2 .
With switch indicator light on, air will recirculate. With switch indicator light off, air will enter from outside of
vehicle.

A/C CONTROL MODULE

The A/C control module (A/C amplifier) is the control unit for the A/C system. See Fig. 2 . The module
receives inputs from various sensors and processes the information to control various outputs for the A/C
system for optimal control.

The A/C control module inputs are as follows:



A/C Switch



In-Vehicle Air Temperature Sensor



Temperature Selector Knob



Blower Motor Knob



Evaporator Temperature Sensor



Air Mix Damper Door Position Sensor

The A/C control module output functions are as follows:



Air Mix Damper Door Motor



All Activity Module



Fresh/Recirculation Door Motor

ALL ACTIVITY MODULE

All Activity Module (AAM) receives inputs to determine if specified conditions have been met to allow
operation of A/C-heater system. If conditions are met, the AAM will send signals to the A/C compressor,
condenser fans relay and the blower motor relay to command or enable operation.

IN-VEHICLE TEMPERATURE SENSOR

The in-vehicle temperature sensor is a negative temperature coefficient resistor. Sensor sends signals to the A/C
control module to maintain in-vehicle temperature. Sensor is located on the center panel of the instrument
cluster.

DUST FILTER

A dust filter provides filtering of air entering or recirculating in the passenger's compartment. The dust filter is
mounted between blower motor and evaporator, below passenger's side of instrument panel, to left of blower

2001 Mercedes-Benz ML320

2000-01 MANUAL A/C-HEATER SYSTEMS ML 320, ML 430 & ML 55

me

motor. See Fig. 2 .

PROGRAMMING

RECODING RADIO

1. Turn ignition on. Ensure CODE is displayed on radio display. Enter code numbers using radio station

buttons. For example, use station button No. 1 for code No. 1 and so on.

2. After first number is entered, CODE disappears and number entered is displayed followed by 4 dashes.

After entering 5-digits, confirm correct security code has been entered. If incorrect code has been entered,
entire code must be reentered.

3. Confirm entry of correct security code using "<" (less than) or ">" (more than) buttons. If an incorrect

code is entered, CODE will be displayed on radio display. If security code is entered incorrectly 3 times,
WAIT will be displayed and radio will be disabled for about 10 minutes.

4. If, after 3 more attempts, correct security code has not been entered, radio will be disabled for 60 minutes.

Radio disable time runs down only when radio is turned off.

VERSION CODING

Version coding is performed using a Mercedes-Benz Hand-Held Tester (HHT) and is on-screen menu guided.
After connecting HHT to DLC, vehicle communication is possible as soon as ignition key is inserted into
ignition switch (position of switch does not matter). Version coding menu, position 1, is reached via main menu
and control module adaptation, position 5. There are 2 possible version codings available: readout of version
code and transfer to new control module or readout of version code and to alter code.

To access A/C system version coding, position 2 must be selected and then position 7 for A/C system. Two
selections can be used: A/C system is installed or A/C system is not installed.

SELF-DIAGNOSTICS

RETRIEVING & ERASING DIAGNOSTIC TROUBLE CODES

Retrieving and erasing of Diagnostic Trouble Codes (DTC) must be performed using Mercedes-Benz Hand-
Held Tester (HHT). See HHT instructions for retrieving A/C-heater system related DTC. After noting codes,
see CLIMATE CONTROL DTC table. To erase DTC, follow HHT instructions.

When retrieving DTC from A/C push button control module, short and open circuits cannot be differentiated
from each other in every instance. When accessing DTC from any control module memory, all stored DTC are
shown. As a result, some DTC shown will not apply to climate control system.

CAUTION: Before disconnecting battery, obtain 5-digit radio security code from

vehicle owner. Radio will be disabled until properly recoded.

NOTE:

Radio will not operate if power supply to radio is interrupted. Obtain 5-digit
radio security code from vehicle owner before disconnecting battery.

2001 Mercedes-Benz ML320

2000-01 MANUAL A/C-HEATER SYSTEMS ML 320, ML 430 & ML 55

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CLIMATE CONTROL DTC

SYSTEM TESTS

CONNECTING TEST EQUIPMENT

Remove radio to gain access to A/C push button control unit harness connector. Turn ignition off. Disconnect
control unit harness connector. Connect socket box Test Cable (163 589 01 63 00) to A/C push button control
unit and wiring harness. See Fig. 3 . Connect test cable to Socket Box (124 589 00 21 00). Connect test
equipment leads to socket box terminals as instructed in circuit tests.

DTC

Possible Cause

B1232

(1)

Refrigerant Pressure Sensor

B1419

Electromagnetic Clutch

(1)

Check A/C refrigerant pressure sensor. See A/C REFRIGERANT PRESSURE SWITCH under
ELECTRICAL TESTS.

WARNING:

To avoid injury from Accidental air bag deployment, read and carefully
follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR
BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in
GENERAL SERVICING.

2001 Mercedes-Benz ML320

2000-01 MANUAL A/C-HEATER SYSTEMS ML 320, ML 430 & ML 55

me