HDJ81 no heat

[Brimmer]

My name is Adam I live in Edmonton Alberta Canada and this is my first post.I was wondering if anyone was experiencing or heard of someone experiencing the same problem as I am with my HDJ81. Recently the heat stopped working in the front but is still working in the rear. I took the heater control out and tested the thermistor it seemed to be faulty so I replaced it still no heat.The truck is running at normal temps and when I open the gate manually to allow hot coolant to enter the heater core the hoses on either side of the gate are warm. Im wondering if there is a secondary valve which directs the air over the core which is not engaging. If so is it tied into the valve on the firewall which is also not engaging when I slide the control over to heat. Sorry about this long winded question.Thanks Adam

 

[roscoFJ73]

My name is Adam I live in Edmonton Alberta Canada and this is my first post.I was wondering if anyone was experiencing or heard of someone experiencing the same problem as I am with my HDJ81. Recently the heat stopped working in the front but is still working in the rear. I took the heater control out and tested the thermistor it seemed to be faulty so I replaced it still no heat.The truck is running at normal temps and when I open the gate manually to allow hot coolant to enter the heater core the hoses on either side of the gate are warm. Im wondering if there is a secondary valve which directs the air over the core which is not engaging. If so is it tied into the valve on the firewall which is also not engaging when I slide the control over to heat. Sorry about this long winded question.Thanks Adam

I would start off with something easy like back flushing the heater core.Disconnect both hoses and put the garden hose in there to flow in the opposite direction.

Being the highest point in the cooling system they can pick up all the floating gunk over the years

 

[Brimmer]

Thanks for the reply that sounds like a good idea, the only thing im wondering is why the valve on the firewall isn't opening on its own when I move the control to heat this is what makes me think it may be an electrical problem. When I manually open the valve there still is no heat is there an internal valve to move the air over the heater core that migh not be engaging that is tied into the firewall valve.

Thanks again
Adam

 

[Brimmer]

Could it possibly be the heater relay? Does the relay effect the control valve?

 

[roscoFJ73]

Thanks for the reply that sounds like a good idea, the only thing im wondering is why the valve on the firewall isn't opening on its own when I move the control to heat this is what makes me think it may be an electrical problem. When I manually open the valve there still is no heat is there an internal valve to move the air over the heater core that migh not be engaging that is tied into the firewall valve.

Thanks again
Adam

I thought the heater valve was opened by cable but Im not an 8o series owner.

EDIT I see there is a lever type and push button type

 

[Brimmer]

It does appear to be a cable that moves the valve im just trying to figure out what controls the cable and why its not working