Tech Tip: Mercedes-Benz A/C Off Light Illuminated, A/C Not Functioning

Tech Tip: Mercedes-Benz A/C Off Light Illuminated, A/C Not Functioning

If you receive customer reports in the above models that the A/C Off light is illuminated and cannot be switched off and the air conditioning is not functional, the Refrigerant Level Temperature Pressure Sensor coding in the AAC unit may need to be set to "INACTIVE." Follow the below procedure to remedy a specification parameter in the refrigerant level logic circuit.

If you receive customer reports in the above models that the A/C Off light is illuminated and cannot be switched off and the air conditioning is not functional, the Refrigerant Level Temperature Pressure Sensor coding in the AAC unit may need to be set to “INACTIVE.” Follow the below procedure to remedy a specification parameter in the refrigerant level logic circuit.

Note: Replacement of the evaporator sensor or the operating unit is not necessary.

Note: Verify that the A/C system is not leaking and is not losing refrigerant.

Models 203, 209, 220 (up to August 2002 production) and 230 (up to August 2003 production)

1. Using STAR Diagnosis, enter the following menus: [Control Units > Air Conditioning > AAC control unit > Actual Values > A/C Control].

2. Observe the value for sensor (B12) Refrigerant Pressure Sensor.

3. Ensure the value for B12 is within specification.

4. Using STAR Diagnosis, enter the following menus: [Control Units > Body > EIS > Control Unit Adaptations > Read Coding and Change if Necessary > Climate Control >Refrigerant Level Check].

5. Set the coding for Refrigerant Level Check ­“INACTIVE.”

6. Select F3 and transfer coding to the control unit.

7. Remove STAR Diagnosis and verify that the A/C Off light is not illuminated by default and will turn on/off after pressing of the A/C Off switch.

Model 211

1. Using STAR Diagnosis, enter the following menus: [Control Units > Air Conditioning > AAC control unit > Actual Values > A/C Control].

2. Observe the value for sensor B12/2 Refrigerant Level Pressure and Temperature Sensor.

3. Ensure the value for B12/2 is within the Specified Value range.

4. Using STAR Diagnosis, enter the following menus: [AAC > Control Unit Adaptations > Read Codings and Change if Necessary > Workshop ­Coding].

5. Set the coding for Coolant level check via pressure and temperature sensor (“Maximum principle”) to “INACTIVE.”

6. Select F3 and transfer coding to the control unit.

7. Remove STAR Diagnosis and verify that the A/C Off light is not illuminated by default and will turn on/off after pressing of the A/C Off switch.

Model 215, 220 (as of September 2002) and 230 (as of September 2003)

1. Using STAR Diagnosis, enter the following menus: [Control Units > Air Conditioning > AAC control unit > Actual Values > Temperature Sensor].

2. Observe the value for sensor (B12) Refrigerant Pressure Sensor.

3. Ensure the value for B12 is within specification.

4. Using STAR Diagnosis, enter the following menus: [Control Units > Body > CGW > Control Unit Adaptations > Read Coding and Change if Necessary > Climate Control > Refrigerant Level Check].

5. Set the coding for Refrigerant Level Check ­“INACTIVE.”

6. Select F3 and transfer coding to the control unit.

7. Remove STAR Diagnosis and verify that the A/C Off light is not illuminated by default and will turn on/off after pressing of the A/C Off switch.

Courtesy of Mercedes-Benz USA, LLC.

You May Also Like

MEMA Celebrates 120th Anniversary

MEMA said the milestone “underscores the association’s enduring legacy and its pivotal role in advancing the future of mobility and the interests of vehicle suppliers.”

MEMA, The Vehicle Suppliers Association, announced its 120th anniversary, a milestone it said "underscores the association's enduring legacy and its pivotal role in advancing the future of mobility and the interests of vehicle suppliers."

MEMA was founded on March 2, 1904, in Cleveland, Ohio, to represent the burgeoning automotive parts manufacturing industry. For the last 120 years, MEMA and its members have been at the forefront of advocacy, innovation and collaboration, the association said.

UniClutch Launches Clutch System in the United States

From Australian manufacturer Clutch Industries, UniClutch is a clutch system that delivers uncompromised performance.

MEMA Aftermarket Suppliers Becomes UAF Gold Lifetime Trustee

The partnership with UAF is a commitment to the future of the automotive aftermarket, MEMA Aftermarket Suppliers said.

Castrol Turns 125, Debuts New Market Strategy

As part of the new strategy, Castrol will explore opportunities in battery thermal management, digital and service solutions and data center immersion cooling.

FCS Introduces 18 New Numbers in February

The new release includes 4 shock absorbers and 14 suspension struts.

Other Posts

Philips Releases GoPure Advanced Automotive Air Purifier

It filters out 99% of bacteria and respiratory viruses and fits in the cupholder.

AP Emissions Releases New Part Numbers for February

The 12 new SKUs cover 6 million VIO.

MANN+HUMMEL NA Aftermarket Shows Right to Repair Support

Representatives from MANN+HUMMEL’s North American aftermarket brands recently visited Capitol Hill to express their support for H.R. 906.

Federated Upgrades Car Care Center Program

The enhanced program features updated signage, marketing support, image-enhancing tools, wearables, business management assistance and other information to help with day-to-day shop operations.