Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
A/C Control And Regulation Components Outside Passenger Compartment
If there is a malfunction in the A/C system, first check the error memory of the Climatronic Control Module -J255- A/C control head using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
If no fault is displayed, read the measured value block for the Climatronic Control Module -J255- A/C control head and activate the component with the output diagnosis test mode function using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
Service the refrigerant circuit.
Servicing operations on A/C system that are possible without opening refrigerant circuit.
Servicing operations on A/C system that require the refrigerant circuit to be opened. Refer to REFRIGERANT CIRCUIT .
The electrical test for various actuators, potentiometers and sensors is described in Guided Fault Finding using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
There are different versions of the Climatronic Control Module -J255- control head. Pay attention to precise assignment on replacement.
A/C system OBD is performed in the Guided Fault Finding function using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
The Climatronic Control Module -J255- A/C control head cannot currently be exchanged as usual, component protection is active at this time using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
If aClimatronic Control Module -J255- A/C control head is to be replaced, check the coding of the -J255- and the adaptation of the -J255- before removal via the Replace control module function of the guided fault finding for this A/C control head, using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
Perform the following work on completion of repair operations:
-- Check the DTC memory for the Climatronic Control Module -J255- A/C control head and erase any faults displayed if necessary using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
-- Check the coding of theClimatronic Control Module -J255- A/C control head using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
-- If necessary, check the adaptation of the Climatronic Control Module -J255- A/C control head using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
-- Perform A/C system basic setting using the Vehicle Diagnostic, Testing and Information SystemVAS 5051.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.