No heat ..AC works fine but no heat

[GardnerM]

Just bought this 2008 cab&chassis nice clean truck as is . Last night wife and I delivered a bid for work and NO HEAT. Temp ga. stays at 190 200 with AC running it hot weather now I find out its got no cab heat. Great after deciding to upgrade to newer!!!

 

[B.G. Smith]

Check the two heater hoses at the firewall with the engine warmed up, both should be Hot. Also look at the hoses and make sure someone hasn't installed a shutoff valve. (it happens) If hoses are hot and no valve you probably have a malfunctioning blend door. bg

 

[GardnerM]

I did the heater treater on my 03 . Hope its somethin a little simpler but ....as is is as is but Thanks Ill check those hoses out.

 

[GardnerM]

Lines coming from firewall both hot. Controls still sending air matching controls ruling out the blend door I THINK.

 

[B.G. Smith]

The air goes through the AC evaporator at all settings, it only goes through the heater core after the AC coil and when the blend door is actuated by the copntrols. Clear as mud? bg

 

[GardnerM]

I do know it's doubtful ,I can deliver this truck to a local diesel mechanic and expect them to pinpoint the problem ,unless they just happened to have been down this road before. And with 267 k road miles , it may have something to do with this God forsaken egr system. I may call a performance shop about 45 miles away to see if they know anything about heater problems related to egr stock system.

 

[GardnerM]

So is it possible for the blend door to be bad if on the hot &cold ? Or could hot and cold switch be shot?

 

[B.G. Smith]

The blend door is operated by an electric servo which is controlled by the temp. knob on your unit. Either part could be defective and cause the door not to move. I believe the blend door is vertical in the unit and the servo motor is on top of the AC housing making it very difficult to get to. bg

 

[GardnerM]

So there is more than one blend door ?? A certfied heater treater installer is across the river from me.Im hoping to pik his brain tommorow.I remember a sequense of symptoms on the heater treater website but couldnt find them.