Heat

[Jl elevatorman]

check for leaf, mice, clogged front of core

 

[kbenz]

Cl

I think the next step would be to disconnect the two heater hoses off of the heater core and connect them together with a piece of clear hose. Fire the truck up and verify that the coolant is circulating. If it is, hook the heater core back up,but keep the clear hose. This way you can verify that the heater core isn’t stopped up.

If you don’t have any flow without the heater core in the loop, it’s time to pull the water pump.


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clear hose showed circulation. Pump and heater core.

 

[renjaminfrankln]

So you can visually see the cable moving the blend door, you get good airflow from the vents when on cold, but when you move from cold to hot the (volume/speed/whatever) goes way down? Sounds like debris blocking the heater core, as others have suggested.

 

[kbenz]

So you can visually see the cable moving the blend door, you get good airflow from the vents when on cold, but when you move from cold to hot the (volume/speed/whatever) goes way down? Sounds like debris blocking the heater core, as others have suggested.

It's not blowing as strong as the ac. and the air is not warm at all.
I have had the heater core out. Everything was clean in there. blend door looked fine. when you switch from ac to heat the temp changes right away but it's not even warm air. the box on the inside of the cab gets warm where the heater core is at

 

[IDIBRONCO]

Maybe there's a blockage in the ductwork behind the dash?

 

[kbenz]

Maybe there's a blockage in the ductwork behind the dash?

you would think the air coming through would at least be warm though. It blows pretty good.

 

[IDIBRONCO]

I don't know. You seem to have covered just about everything else. I was just trying to throw out other suggestions.

 

[kbenz]

I don't know. You seem to have covered just about everything else. I was just trying to throw out other suggestions.

I appreciate it. Just got me baffled

 

[IDIBRONCO]

Your heater core box gets warm/hot while the engine's running. Air blows out of the vents, but isn't even warm while the temperature control is set to "hot". It seems like your problem is somewhere in the parts that control how much hot air goes through into the duct work. Isn't there a door that controls the hot air flow? Not the blend door.

 

[kbenz]

Your heater core box gets warm/hot while the engine's running. Air blows out of the vents, but isn't even warm while the temperature control is set to "hot". It seems like your problem is somewhere in the parts that control how much hot air goes through into the duct work. Isn't there a door that controls the hot air flow? Not the blend door.

could the selector switch cause this? not the cold to hot blend door but the switch for ac/max ac/vent/defrost/floor

 

[IDIBRONCO]

I kind of doubt it. No matter where that is set, the temperature should still change. It should put out hot air to any of the vents if it wasn't working. It has to do with temperature, not vent location.

 

[kbenz]

I was messing around today and discovered I get heat out of the ac vents when I have temp knob turned on heat and selector knob on vent, norm ac or max ac

 

[kbenz]

This

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[gnathv]

Is your compressor also running in that position?

 

[kbenz]

Is your compressor also running in that position?

I'll have to check. lines had frost on them. If I turn the temp knob to cold it kicks cold air