No heat

1989 GMC TRUCK
190,000 MILES • V8 • 4WD • AUTOMATIC
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Hi I have the truck listed above V3500 with no heat. The heater core hasn't been bypassed and I don't smell any syrup in the cab. I also don't slowly lose any coolant. the blower motor works and the switches for the air all work. so I have no clue as to what it could be. Also it has the 454 and it's a dually.
Apr 27, 2019 at 10:37 PM
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ASEMASTER6371
  • ✓ASE Certified Mechanic
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  • ASE Certified Mechanic
Good morning,

I would start by making sure the thermostat is working and the coolant is getting hot enough.

https://www.2carpros.com/articles/car-heater-not-working

https://www.2carpros.com/articles/replace-thermostat

I would also remove the heater hoses from the firewall and flush out the heater core with a garden hose until you get equal flow to both sides.

Make sure the blend door is responding correctly with commanding heat.

Roy
Apr 28, 2019 at 4:43 AM
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