2021 Mercedes-Benz AMG GT HVAC Concerns Diagnostic TSB

Mercedes-Benz has released Technical Service Bulletin (TSB) L183.30-P-079850 to provide guidance for diagnosing various heating, ventilation, and air conditioning (HVAC) concerns. This TSB applies to the 2021 Mercedes-Benz AMG GT, among other Mercedes-Benz passenger cars, and addresses common complaints about the AC system's performance.

Owners of a 2021 Mercedes-Benz AMG GT HVAC concerns may notice their air conditioning not cooling effectively, performing poorly, or the heating system providing insufficient warmth. This document serves as a general diagnostic framework for technicians to systematically approach these issues.

Symptoms

Owners may experience a range of symptoms related to their Mercedes-Benz AMG GT HVAC concerns. The TSB lists the following potential issues:

• Body > Air conditioning > Heater > Remains cold
• Body > Air conditioning > Heater > Remains warm/hot
• Body > Air conditioning > Heater > Insufficient heat output
• Body > Air conditioning > Heater > Cold in footwell
• Body > Air conditioning > Air conditioning > Insufficient cooling output
• Body > Air conditioning > Heater > Malfunction, defrosting
• Body > Air conditioning > Heater > Footwell flap cannot be opened/closed
• Body > Air conditioning > Air conditioning > Temperature differences
• Body > Air conditioning > Air conditioning > Cooling output too high
• Body > Air conditioning > Heater > Center air vent does not close
• Body > Air conditioning > Air conditioning > Temperature control not sensitive enough

Important Warnings for Owners

This TSB contains critical information for both technicians and owners regarding proper diagnostic methods and warranty coverage:

• Refrigerant Leak Testing: The TSB explicitly states: "Forming Gas is the ONLY approved leak test method. (DYE is NOT approved)". This means technicians should not use dye for leak detection in your vehicle's AC system.
• Warranty Disclaimer: Mercedes-Benz notes: "DO NOT assume that a symptom or condition, or a described cause of a symptom or condition, affects any particular vehicle or groups of vehicles... The information contained in this document... does not guarantee warranty coverage nor does it extend the vehicle's warranty in any way."

Diagnostic Approach

The TSB outlines a general diagnostic process for technicians to follow when addressing Mercedes-Benz AMG GT HVAC concerns. This includes several initial steps:

1. Verify Customer Concern: Confirm the exact issue reported by the customer.
2. Compare to Like Vehicle: Determine if the behavior is normal by comparing it with a similar vehicle.
3. Determine Diagnostic Strategy: Identify the appropriate diagnostic strategy and the components or systems involved.
4. Testing: Perform all relevant diagnostic tests.

Key Diagnostic Measurements

For thorough diagnosis and warranty submission, specific measurements are required both before and after any repairs. These include:

• Refrigerant Quantity: Technicians must record the amount of refrigerant recovered and compare it to specified values. As noted, forming gas is the only approved leak test method.
• Cooling Capacity Test: If the system has a charge, a cooling capacity test is necessary.
• Gauge Readings: High and low-pressure readings from the AC system must be taken using a machine or separate gauges.
• Leak Detection: If applicable, any parts per million (PPM) of leaks found must be documented.
• XENTRY Printouts: Printouts of climate control Actuator Values (AVs) and High Voltage (HV) compressor AVs (for heat and AC systems) are required.
• Thermometer Readings: Temperature readings from the left and right dash vents, and center, footwell, and/or rear vents (if the concern is localized) are essential.
• Ambient Conditions: Temperature and humidity readings from the Overhead Control Panel (OCP) AVs, if available, should be recorded.

Warranty Documentation Requirements

When submitting a warranty claim for a repair related to Mercedes-Benz AMG GT HVAC concerns, technicians must adhere to specific documentation requirements. This includes detailing the complaint analysis, the diagnostic strategy (Game/Players), and the testing steps performed. They must also include expected results, technical justification for the diagnosis, and the root cause. It's important that all prior measurements are documented on the repair order, and technicians should avoid simply listing 'Repair and Inspection' (R/I) steps, focusing instead on the diagnostic reasoning.

Operation Codes

The TSB references several operation codes related to diagnostic procedures for HVAC systems:

• 831232: Max .5 for Cooling Capacity Test
• 831040: To be utilized only if there is a fault code and active diagnosis of that fault code
• 831762: This includes basic leak check
• 831285: Can only be used in extenuating circumstances where a leak cannot be found

These codes are primarily for internal Mercedes-Benz use for tracking and billing diagnostic time.

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NHTSA ID: 11027566