Leaking Evaporator Core Seal

Some 2016-2018 CT6 models may have decreased air flow at the instrument panel outer air vents while the vehicle is moving. The air conditioning evaporator core seal may not be sealing completely, allowing warm air to pass between the evaporator core and housing, which hits the evaporator temperature sensor and causes a false high reading. As a result, the compressor may continue to run and cause the evaporator to ice up. (Fig. 15)

Fig. 15

If this condition is found, replace the seal around the evaporator core. (Fig. 16) The repair requires the removal of the instrument panel carrier and instrument panel tie bar. Refer to Bulletin #18-NA-052 for more information.

Fig. 16

The CT6 uses an R-1234yf refrigerant system. To remove, recycle and install R-1234yf from/to a vehicle’s refrigerant system, use the GE-50300 R-1234yf Air Conditioning Refrigerant Recovery/Recharge Cart or refrigerant/recovery/recharge equipment certified to meet the requirements of SAE J2843 and approved by the EPA.

After installation of the evaporator core seal, also perform the HVAC Actuator Learn procedure in the HVAC control module. Do not operate the climate controls while the HVAC control module is calibrating.


– Thanks to Blake Streling

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  1. A new seal was developed to more effectively prevent warm air bypassing the seal. The new seal will be available soon.

  2. Brett Mount says:

    We tried ordering this seal per TSB instruction but GM has since stopped shipping them. Instead, they are currently “exploring other solutions”. We’ve had to put our customer back in his vehicle and asked that he wait until GM has a new/better repair.

  3. ALAN BAGWELL says:


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