Fault Code Guide

If a leak exists in the system and it cannot be traced
to other parts or fittings, suspect damage to one of
the evaporator coils.
Condenser
The condenser is usually trouble-free. Normally, the
temperature of the condenser outlet line is noticeably
cooler than the inlet line. However, when road debris
such as leaves or dirt build up, the airflow over the
condenser fins is blocked. Air is not able to absorb
enough heat to turn the hot refrigerant gas into a liq-
uid. High head pressures will result. In these cases,
carefully clean the outer surfaces of the condenser
with compressed air or a soap and water solution. Be
careful not to bend the fins.
High head pressures will also occur if the condenser
tubing is abnormally bent, blocking the flow of refrig-
erant. Frost will appear at the point where the flow is
restricted.
Less common internal blockages, such as bits of for-
eign material or metallic grit buildup, will stop the
flow of refrigerant.
When troubleshooting a suspected condenser prob-
lem, remember that the problem may be caused by
the radiator transferring high levels of heat to the
condenser. See Group 20 of this manual for cooling
system troubleshooting, and see the engine manu-
facturer’s service manual for other information about
cooling system problems.
Line Restrictions
A restricted suction line causes low suction pressure
at the compressor and little or no cooling. A restric-
tion in a line between the compressor and the expan-
sion valve can cause high discharge and low suction
pressure, and insufficient cooling.
Areas of ice or frost buildup usually mean a block-
age. Parts that often freeze are probably corroded or
inoperative and should be replaced. Parts, such as
the expansion valve, that freeze once in a while may
do so because of moisture in the system. If this hap-
pens, recover the refrigerant charge, evacuate/
recycle the system refrigerant, replace the receiver-
drier, and recover, evacuate, and charge the system
with refrigerant.
Temperature Blend Door
Actuator Circuit Tests
The temperature blend door actuator controls the
amount of air that is routed through the heater core.
The temperature blend door actuator is controlled by
the temperature control switch on the control head
(climate control panel). The control head senses the
door position by reading the feedback voltage from
the actuator position sensor. The feedback voltage
will be less than the 5V reference voltage sent by the
control head to the sensor.
The target position is based on the temperature con-
trol switch setting and internal control head algo-
rithms. The desired position is considered reached
when one of the following conditions is true, although
this does not necessarily mean that the position actu-
ally corresponds to the desired temperature setting
(for example, if the actuator movement is limited due
to an obstruction).
• The actuator feedback position has been
reached.
• The actuator is stalled for more than 1 second;
the actuator feedback position does not
change for more than 1 second.
• The target position corresponds to an end stop
and an additional 1 second extra drive in the
same direction (to guarantee sealing) has been
performed.
The temperature blend door should move from one
extreme position to the other when turning the tem-
perature control switch from cold to hot or from hot to
cold.
Follow the tests in Table 3 in the sequence pre-
sented. The directions under the column "What to Do
if Test Fails" are sometimes dependent on good re-
sults from previous tests. If any of the tests fail, stop
and perform the specified repair or check. If the tem-
perature blend door actuator passes the tests in
Table 3 and the actuator still does not operate prop-
erly, check for mechanical problems with the actua-
tor.
Cab Heater and Air Conditioner, Valeo 83.00
Troubleshooting
Business Class M2 Workshop Manual, Supplement 13, March 2008300/8