Rear Heater Air Temp Low During Extreme Cold Weather (Replace Rear Heater Tee Couplings)

Some customers may comment on insufficient heat from the rear heater during periods of extreme cold weather.

A restrictor in the tee coupling located at the heater core inlet and outlet limits the coolant flow to the rear heater core.

Replace the original inlet and outlet heater tee couplings with revised couplings that have an increased inside diameter to improve coolant flow. Use the following procedure and the part numbers listed below.

1. Open the hood.
2. Drain the coolant. Refer to the Engine Cooling subsection of the Service Manual.
3. Disconnect the main heater hoses from the heater tee connectors.
4. Remove the clamp retaining the accumulator. Reposition the accumulator as required in order to gain access to the tee clamps.

Notice: The original quick connect fittings on the heater tees are made of a plastic that will not allow sufficient flexibility to release the connectors without breaking them. It is advisable to crack the quick connects to aid in releasing them. The revised heater tees include replacement quick connects. Do not use force that will pull on the heater core or damage the inlet or outlet pipes.

5. Disconnect the rear heater hoses from the tee connectors.
6. Disconnect the heater tees from the heater core.
7. Install revised heater tees (tan - inlet tee; black - outlet tee) to the rear heater hoses.
8. Install the tee connectors to the heater core.
9. Connect the main heater hoses to the heater tees.
10. Refill and bleed the cooling system. Refer to the Engine Cooling subsection of the Service Manual.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: