Heat not shutting off when in AC looked for heater control valve none exist and both units operated fine for 2 years with no parts change

Bryan Cobb

Asked by Mar 28, 2016 at 10:34 AM about the 1998 GMC Sierra 1500 K1500 SLE 4WD Extended Cab SB

Question type: Maintenance & Repair

1 Answer


You won't find a hot water shut off anymore, everything is handles by blend doors and servo motors, so checes are very high the you have either a broken blend door or the servo motor has quit operating. Heater box work can get expensive very quickly, as with most vehicles today any kind of heater box work requires the entire dash to be remove to even gain access to the system. It would have cost a grand to have fixed my Jeep if I didn't know how to it myself.

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