Heater not working right acting like a vacuum leak

Asked by Guru9931WX Nov 29, 2021 at 10:11 AM about the 1988 GMC Sierra 1500 C1500 Standard Cab SB

Question type: Maintenance & Repair

Heater seems like it has a vacuum leak at idle it starts to
blow cold air but off idle it blows hot but don't have a
vacuum hose to the air box

1 Answer

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