Have an 01 standard 24v standard output with the heater not as hot as it should be. Replaced the heater core, thermostat, and water pump and the air temp out of the vent is about 100-105 degrees at the most. The diesel shop said the blend door is fine and working. If I try to adjust the temp ****, the vent temp stays the same until its one click to the left of the middle and then it's cool air with no gradual change in the air temp. Any ides what to check or replace next?

 

How is your coolant level? Could anything be leaking? I replaced my heater core, and hoses. They needed replaced, but it ended up being the gaskets for the water pump and the one on the pass side of the motor by the lower rad hose (big pain, have to remove the whole A/C Bracket). You can usually see the streaks from where it has been leaking on the block. I replaced my head gasket before all of this and never washed the motor down so I couldn't tell it was leaking. Hope this helps and you get it fixed.

 

Did the head gasket last summer. Had it in the shop last week actually for the same gasket behind the ac bracket and it didn't change anything. The coolant is full and not looking.

 

For not hot enough, have you replaced the fitting that goes into the head from the heater core? It's inner diameter is small. It can be drilled out, or simply replaced. This will allow more flow through the heater core.

I would try and watch the shaft for the blend air door as you slowly rotate the heat ****. Or get someone to turn as you watch. You should be able to see the shaft sticking out of the HVAC box on the bottom.

 

Possibly your new tstat is defective.

 

I would say start with another new tstat also.

 

I can see the blend motor turning as I turn the temp control **** and I haven't thought about drilling out or replacing the fitting going into the heater hose. But when I turn the **** there is no change in the temp of the air blowing out. Whether it's in the middle or all the way to the way to the right, its the same unless you turn it one click to the left and then it's cold. And no change from the ac if it's all the way to the left or the middle its all the same cold temp unless its one click to the right of middle then it's warm.