No heat, not sure what the problem is.

[mrmauser98]

I recently acquired a 97 k1500, and then I found out the heat didn't work .

I had an 05 Silverado years ago and had replaced the blend doors in it so I kind of just went that direction with some cheap ones off Amazon.

So I started off replacing the one for the vents near the gas pedal. While doing it I noticed neither the new one( I actually tried the two new ones) or the old one rotated very far at all, maybe a few 1/16ths of an inch back and fourth. At the same time I found out why the truck is stuck on defrost, the flapper for that one is messed up, it was unhooked from the bracket system and the rod and lever move about freely and in out. I don't know if I will actually fix that issue I assume the dash needs taken apart.

So Instead of replacing the heater blend door I took the dash apart and watched it, it does respond to me moving the control switch but in the same way as the actuator for the vents, barely moving back and fourth. I found a video on YouTube that clearly showed the actuators moving much farther back and fourth then mine.

I'm not sure what my next move should be? Replace the HVAC control switch ? At the moment all I care about is getting some heat in this thing so I can drive through the Indiana winter . My thoughts are send back the blend doors, and get an HVAC control unit. Thank God for Amazons return policy, really helps for shotgunners like me.

 

[1998_K1500_Sub]

I recently acquired a 97 k1500, and then I found out the heat didn't work .

Should I assume you've confirmed the heater core is hot / there's hot coolant flowing through the heater circuit? Engine thermostat is working properly? I hate to ask but...

I know a guy who struggled for over a year with an engine / ECU swap in a Dodge pickup. He completed it in 2022, and he did a nice job mechanically. The engine would start, but it would then die after about 2s. Over the next 12+ months various people looked at it. Nobody could find or solve the problem, so last week I looked at it for him; it turned out to be a poor ECU power ground. How simple was that???

 

[mrmauser98]

Should I assume you've confirmed the heater core is hot / there's hot coolant flowing through the heater circuit? Engine thermostat is working properly? I hate to ask but...

I know a guy who struggled for over a year with an engine / ECU swap in a 2002 Dodge Dakota. He completed it in 2022, and he did a nice job mechanically. The engine would start, but it would then die after about 2s. Over the next 12+ months various people looked at it. Nobody could find or solve the problem, so last week I looked at it for him; it turned out to be a poor ECU power ground. How simple was that???

No I haven't checked that yet, it's on my long list of stuff. Just didn't seem right with the actuators moving so little.

 

[GoToGuy]

You have no history or only a little experience with a new truck. Any problems I would start at the most basic diagnostic. No heat? What's the water temp. Is water flowing through the heat exchanger, or is it clogged with rust and dirt? Are the door flap position modules moving with knob selected positions. And so fourth.

 

[east302]

No I haven't checked that yet, it's on my long list of stuff. Just didn't seem right with the actuators moving so little.

The heater air door is behind the ashtray but is the same part number as the mode door that you’re looking at by the gas pedal.

The notch on the silver dial will rotate between the lines on the actuator housing.

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If the new and existing ones don’t turn, see if the three dampers rotate freely and that the linkage arms are intact:

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To check the control to the actuator, disconnect and test the voltage at the connector. It’ll have three wires - ground, battery and signal. I forget which is which, but stick a meter to the pins and confirm 12V on the battery wire. On the signal wire, see if the voltage varies while you turn the mode (floor-panel-defrost) dial. You should see around 12V on dash, 6V on floor and very low (1V or less) on defrost.

If the signal voltage doesn’t vary, then the problem is probably the panel or wiring in between.

The heater door actuator rotates and tests the same way with the temperature dial.

If the actuator is instead sticking or making a ratcheting sound, the gears are probably shot.

You must be registered for see images attach

 

[mrmauser98]

. P

The heater air door is behind the ashtray but is the same part number as the mode door that you’re looking at by the gas pedal.

The notch on the silver dial will rotate between the lines on the actuator housing.

You must be registered for see images attach

If the new and existing ones don’t turn, see if the three dampers rotate freely and that the linkage arms are intact:

You must be registered for see images attach

To check the control to the actuator, disconnect and test the voltage at the connector. It’ll have three wires - ground, battery and signal. I forget which is which, but stick a meter to the pins and confirm 12V on the battery wire. On the signal wire, see if the voltage varies while you turn the mode (floor-panel-defrost) dial. You should see around 12V on dash, 6V on floor and very low (1V or less) on defrost.

If the signal voltage doesn’t vary, then the problem is probably the panel or wiring in between.

The heater door actuator rotates and tests the same way with the temperature dial.

If the actuator is instead sticking or making a ratcheting sound, the gears are probably shot.

You must be registered for see images attach

Thanks a ton for this information ! My actuators are moving 1/10 of that range, I'll get my multimeter out and do some testing today.

 

[mrmauser98]

My heat issue was my heater/ac control unit. It was kind of obvious when I looked at it upon removal one of the wires on the circuit bored was fried. New unit and I've got heat again.