BMW 3 (E46). Manual — part 282

Cooling System

.

Servicing the A/C system requires the
use of specialized equipment. Follow the
equipment manufacturer's instructions.

Rear window defogger

The electric rear window defogger switch
is integrated in the IHKA control panel.
Pressing the rear window defogger
button activates the rear window heating
element for about 17 minutes, although
this can be changed through Car
Memory settings. Pressing the button
again activates a cycle of 40 seconds
on/80 seconds off for 5 minutes.

The defogger element in the rear glass
is integrated with the radio antenna.

The rear window defogger relay (arrow)
is located in the right side of the luggage
or cargo (Sport Wagon) compartment
behind the trim.

Convertible heated rear window

In the E46 Convertible, both the soft top
and the hard top are equipped with rear
window defogger. Power is supplied by
two relays located on the right side rear
quarter panel behind the interior trim
cover.

Rear defogger operation is controlled by
the IHKA control module.

On hard top:

Rear relay is energized.

Power to hard top window is
supplied through connector strip on
hard top lock.

On convertible top:

Rear relay is energized. It powers
front relay.

If convertible top control module
(CVM) signals that convertible top is
locked to windshield frame, front
relay powers rear window heater
grid.

If convertible top is lowered, a
signal from CVM to front relay
prevents heated top operation.

Front relay also signals sound
system to switch stereo sound ON
when top is up, stereo sound OFF
when top is down.

Solar sensor

The purpose of the solar sensor is to
detect and relay information about the
amount and intensity of solar heating to
the IHKA control module. The settings of
the climate control system are changed
to compensate for this additional
influence.

The solar sensor consists of a
photoresistor installed in the right
defroster outlet and a short harness.

The solar sensor receives power (5 volts)
and ground from the IHKA control

module. The module then calculates
voltage drop across the photoresistor
and determines the degree of solar
heating based on the change in voltage.
Voltage drop across the photoresistor
increases as solar radiation increases.
The IHKA control module processes the
photoresistor input every 10 seconds
and also checks it for plausibility based
on mapped values. Values outside the
limit indicate a malfunction and the solar
sensor signal is ignored by the module.

The IHKA module regulates interior
climate settings using the following:

Blower. The blower activation curve
is changed.

Ventilation. The opening angles of
air distribution flaps are changed.

Troubleshooting of the solar sensor is
carried out through the IHKA diagnostic
program incorporated in DIS or MoDiC.
The IHKA control module may set codes
indicating a short or an open circuit.

To access the solar sensor, remove the
trim in front of the main dashboard
panel, ahead of the dashboard vents.

Troubleshooting

Trouble with the heating and A/C system
can be broken down into one or more of
the following categories.

Mechanical problems

Control head malfunction

Blower motor malfunction

Noisy or seized compressor

Noisy compressor clutch

Malfunctioning belt

Diagnosis of noisy engine compartment
components is covered in

100

Engine–General

. A/C belt replacement is

covered in

020 Maintenance

.

Cooling system problems

Coolant problems

Cooling fan problems

Cooling system pressure testing and
other diagnosis is covered in

170

Radiator and Cooling System

.

Refrigerant leak

Use diagnostic equipment to pinpoint
refrigerant leaks. Replace leaky
components or seals.

Note:

Diagnosis of A/C system components is
beyond the scope of this manual. Follow
the equipment manufacturer's
instructions.

Odors

MIldew in the IHKA housing and in the
evaporator fins can cause strong odors.

Working under right side of dash,
remove blower fan resistor pack (arrow)
as described later in this repair group.