GM and GMC

What is the probable cause if a 1991 GMC pickup heater suddenly stopped blowing warm air?


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Wiki User
2004-10-28 20:08:05
2004-10-28 20:08:05

Heater Control Valve IF there is Vaccume going 2 it.Butt feel both heater hoses & if the Valve is bad - only one hose will b HOT.


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Which part isn't working? Is it blowing air but it stays cold, is it not blowing at all or is it just blowing to the defroster?

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What do you mean by "has no heat"? No air blowing out, blowing out cold air when heater is on, blowing nothing at all? Heater not turning on? What specifically is happening?

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No one knows if:The heater is NOT blowing - or blowing on high speed only, or... The heater IS blowing, but the air is NOT hotEither way, the "Related Questions" below will get you started

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The water is not circulating through the heater core or you have a control problem. If the heater is putting out heat then it is probably a control problem. If no heat then - water pump out, low on coolant, or maybe the therostat is stuck open.

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