99 Tahoe no heat

[wykyd]

I'm thinking it's the blend actuator, how much should the actuator turn when activated? It looks to move about a quarter of a turn. I do hear an audible difference in sound when switched from cold to hot but no difference in temperature. One of the hoses on the core is noticeably cooler for a while after letting it warm up but they both eventually feel to be the same temp. I have a new heater core on the way just in case, nice to have a spare if I don't need it considering it will fit both of my trucks.

 

[sntrym95]

All of the actuators in these trucks turn about a quarter turn to move between their settings. There are 3 - the recirc door, the blend door, and the position (floor, vent, defrost). If the door is turning, and you can see it turning, then it's probably working fine. I would check to see if the heater core or the AC core is blocked by dirt/debris. You can access it by removing the blower motor, and shining a light into the HVAC box.

 

[wykyd]

Turned out to be the heater control valve. Good to know about how much they are supposed to turn though. Thanks for the reply.

 

[gary350]

My heater stopped making heat turns out it was the cooling system thermostat was bad. Look at the temperature gauge on your dash does it show HOT after the engine warms up or does it show cold after the engine warms up. If the dash gauge shows engine is cold all the time change the cooling system thermostat 5 minute job with a 9/16 socket & ratchet.