SECTION 22: HEATING AND AIR CONDITIONING
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
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3. HVAC SYSTEM OPERATION
To operate the air conditioning system when
vehicle is stationary, engine should run at fast
idle. During operation of the air conditioning
system, windows should be kept closed and
door not left open longer than necessary. In
order to prevent battery discharge, the HVAC
system will not operate if the battery voltage
drops below 24 volts.
3.1 HVAC
CONTROL
UNIT
The vehicle is divided into two areas:
1 - Driver’s area (driver’s HVAC unit)
2 - Passengers’ area (passengers’ HVAC unit)
Fresh air is fed in each area and has a separate
return air and discharge air duct.
Both driver and passengers HVAC units turn on
automatically at starting of the engine but the
driver can turn both off if desired and can then
turn them back on using the ON/OFF button on
the HVAC control unit.
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The HVAC control unit is used to control
heating, ventilation, air conditioning and
defroster in the driver’s area only. The
passengers’ area HVAC unit (passengers’ unit)
temperature and fan speed is fully automatic. It
has a preset temperature of 68°F (20°C). The
temperature and fan speed cannot be changed
by the driver.
NOTE
It is recommended to run engine at fast idle to
operate the air conditioning system when
vehicle is stationary.
This will improve A/C compressor performance
and provide adequate electrical power to the
multiple A/C system fans.
When the system is running, keep roof
ventilation hatch and door closed to prevent
cooling loss.
To prevent battery run-down, the central HVAC
unit will not operate if the battery voltage drops
below 24 volts.
When the HVAC system is in operation, park at
least 4 feet from other vehicles or buildings to
allow sufficient air flow through the condenser
coil.
The HVAC control unit performs a self-test every
time it is turned on. Codes are shown on
displays or flashed on control buttons.
The A/C compressor starts automatically when
the two following conditions are satisfied:
1. The outside temperature is above 32°F
(0°C).
2. The passengers’ area temperature is
within 7° of the set point or higher (set
point is 68°F, so return air temperature
must be above 61°F, at this moment,
enough heat is available from the engine
to warm up the area while the air
conditioning will remove moisture in air
and prevent fogging up of the windows).
NOTE
Upon starting, if the outside temperature is
above 32°F (0°C) and then drops below 32°F
(0°C), the compressor will keep running
down to a temperature of 15°F (-9°C) to
prevent fogging up of the windows.
The driver’s HVAC unit piping is paralleled with
the passengers’ HVAC unit piping. Both sections
use the same refrigerant and hot water, and are
linked to the same condenser and compressor,
even if they are individually controlled. In order
for the driver to have air conditioning, the
passenger air conditioning system must be
operating (A/C compressor must be operating).
NOTE
The driver's and passengers’ HVAC unit turn
on automatically at starting of the engine
(multiplex receives the “engine running”
signal) when the multiplex system receives
an “engine running” signal.
NOTE
To perform a test of the driver's section
windshield defroster, it is possible to run the
system without running the engine.
The following table can be used for
troubleshooting the following temperature
sensors:
