No Heat.

I've done a good bit of research and what I think is logical trouble-shooting.

No heat.. very mild heat in the rear.

Blower motor/fan speed only works on high - changed out the resistor with no affect.. I may have damaged the new resistor on installation... no issue right now...

Replace the thermostat.. it works as it opens/closes normally.. engine never gets near 212 but it seems normal.

Replaced the vacuum-operated heater control valve, the old one probably worked but it's cheap. The vacuum line was dry rotted and disconnected, that's all fixed. The heater control valve solenoid does get 12 v when the temperature selector is on MAX A/C... but not sure if the solenoid is actually working... again no issue because I want heat.. and in it's normal state the heater control valve allows hot coolant into the front heater core.

Replaced the heater core because A) it's cheap and B) it's easy.

Both blend control/servos work as I can feel the motor axle turn and the air deflection works i.e. defrost to the windscreen, lower to the feet, etc. The blend control on the heater core.. I assume the door is actually moving.. the servo works.

I bled the entire system pretty thoroughly.. it was low... and it bubbled out as expected, like when the thermostat opened, etc.

Here's the thing.. the hoses leaving the heater control valve don't feel as hot as the ones leading to it... certainly not as hot as the top radiator hose. And I'm wondering the the top/inlet hose to the heater core is simply hot to the touch because it's relatively near the exhaust manifold.

So... sort of at a lost.. and cold actually. I've thought about removing the heater control valve altogether to eliminate it as a possible problem.. the A/C does not work anyway and right now I just want heat.

What's next? I can take it to my shop... but I'd love to solve this problem myself.

 

Looks like you covered all the bases, I would relace the thermostat with GM product. I had to replace my original one @ 170K, it was stuck partially open. The thermostat is what controls the heat. JMHO
david

 

What temperature / where on the (dummy) gauge should this truck read to be 'normal'? I've seen posts suggesting smack in the middle/212 is the nominal temp - mine never gets there.. granted it's winter and we're not at load

 

The return should be a wee bit cooler as the heater core acts like a small radiator so some heat loss is expected...

as for the control valve I agree that removing it may help with troubleshooting...