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2000 GMC SIERRA HEATER WONT BLOW HOT HEATER CORE IS GOOD


is the blower fan

is the blower fan running?
when you swicth modes from hot to cold, can you hear the blend door change/move?
is it a new core/flushed?
tryed starting with one heater hose off?
what size engin, i can check bulletins for you.

Check the coolant level. when

Check the coolant level.
when engine is at normal temp, check the heater hoses (underhood) to see if they are hot (each about the same temperature).

If all of this is OK, check the actuators which switch the blower housing from heat to cold air and from vent to defrost to floor. You can see the actuators move as you switch from one setting to the next.

Check vacuum going to the heater control valve (follow the heater hoses tot he control valve). On some modle you can hold them open to see if the heater blows out hot air while it is held open. If so, and it gets vacuum, repalce the heater contol valve.

If all of this is OK, suspect a clogged heater core, in which case you'll have to disconnect the heater hoses and use a garden hose to flush out the heater core.

there's a few gm bulletins

there's a few gm bulletins out on heating and a/c, if you like i can post them.
also this system is eletronic so codes can be set in the hvac module, i'd have them checked befor any parts are replaced.

good point. However check the

good point. However check the more prevalent items first. According to the repair info I've read, this should be done before suspecting the electronics.


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