I have a 1989 GMC Sierra 2500. within the past few weeks, my heater has started blowing cold air. But, it doesn't constantly blow cold air. It goes back and forth between hot and cold. Does this mean my heater core is bad, or may it be another problem?

5

Asked by Nov 13, 2013 at 01:58 AM about the 1990 GMC Sierra 2500

Question type: Maintenance & Repair

I have a 1989 GMC Sierra 2500. within the past few weeks, my heater has started blowing cold air. But, it doesn't constantly blow cold air. It goes back and forth between hot and cold. Does this mean my heater core is bad, or may it be another problem?

3 Answers

1,535

Its sounds like you have a ac and heater vacuum control valve that has gone bad also make sure there is plenty of antifreeze in the radiator

2 people found this helpful.
1,535

Also check the hoses on the valve as well

2 people found this helpful.

Check your temperature gauge if it's going up and down your probably air locked in your upper radiator hose.

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