01273 - Fresh Air Blower (V2)
010 - Open or Short to Plus
Fault Status: 01101010
Fault Priority: 3
Fault Frequency: 1
Reset counter: 91
Mileage: 138043 km
Time Indication: 0
Speed: 0.0 km/h
(no units): 185.0
Load: 0.0 %
As you can see the fan runs correctly at all 12 speeds, the issue is that it stops the Air con Compressor from engaging.
Clear the code and it will engage for about 10 seconds and kick out again.
This is climate but does not have the additional rear blower.
J126, J255 and V2 are Genuine new. I have seen the invoice with the correct Reg no.
I am convinced that the issue is the feedback wire. The terminal on J126 is marked "DIAG"
Unplugging the Fan V2 or the control Unit J126 or both does not entice additional DTC's. That's some reassurance that I am on the right track.
SSP361 page 66 - 67
Fresh air blower control unit J126
The fresh air blower control unit J126 controls the
blower speed in the deluxe automatic air conditioner
and the four-zone deluxe automatic air conditioner.
In the manual system, a series resistor is installed in
The sender is activated by the Climatronic control
unit J255 via an analogue signal.
The Climatronic control unit J255 is connected to the convenience CAN bus, It is the master control unit for
the distributed functions of the heated rear window, the optional heated seats, the additional heater in the
case of diesel engines, as well as the optional, factory-installed auxiliary heater.
The Climatronic control unit J255 does not control any modules connected to the LIN bus. The fresh air blower
control unit J126 and the high pressure sender G65 are not connected to the LIN bus. Serial data telegrams
(PWM signals) are used.
SSP 301 Page 73
blower control, front G462
In the 4C-Climatronic and the 2CClimatronic,
this is inserted immediately next to
the blower in the housing of the air-conditioning
unit and secured by two screws. In the manual
air-conditioning system, a protective resistor is
installed in place of the regulator.
The sender for blower control is activated by the
Climatronic control unit using a pulse widthmodulated
Power is supplied to the control by the
Climatronic control unit J255.
According to its demands, the sender regulates
the blower motor in the air-conditioning unit.
Effect of drop-out
If a blower is defective, the entire heating and
cooling function of the air-conditioning system
The diagnostics can be used only indirectly to
localise a fault on the blower control unit or on
the blower. For this purpose, there is a resistor in
the blower control unit; this is connected with the
minus pole of the blower motor.
Due to this arrangement, the control unit receives
”acknowledgement information”, which can be
used to determine whether the fault is at the
sender, at the blower or both.
There is no direct indication for a fault on the
control or on the blower.
However, the voltage signal of the resistor in the
blower control is not a signal for the actual
voltage on the blower motor, but rather a signal
with which the Climatronic control unit can
”observe” the behaviour of the sender for the
With a view to pin the fault on either J126 or J255 I cut the feedback wire and scoped both ends of it