1999 EB 4X4 - Something doesn't seem right with the heater in the Expy. When I set the temp to 90 and press the vent only cold air comes out. At times while driving I'll turn it off and then back on and it'll start blowing out hot. Turn it off then on and it'll blow cold.???? I checked the coolant resevoir and it is at max level. These trucks don't have the conventional cap on the radiator so could I actually be low on coolant? I looked up the owners manual and checked any and all fuses related to the hvac system and all are ok. Am I missing something here? Any help would be appreciated.

Eric

 

You may find additional information searching key words "blend door".

 

I Would Change The Termostat 8 Dollars To 15 At Auto Zone. How Many Miles Do You Have On It?

 

Just turned 90k

 

I'm having a similar problem, however the rear heat works just fine. Front heat blows cold. Could this be attributed to the blend door?

 

the blend door will routes air through your heater core or around it for hot or cold air if you turn it on and off and then back on and it changes from hot to cold i doubt it is your coolant system cousing your problem the blend door is sticking or not operating correctly