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Randall C
Randall C, ASE Master Tech
Category: Chevy
Satisfied Customers: 12695
Experience:  ASE Master, L1, 32 years, Diagnostic / Electrical Specialist
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My Chevy Silverado 1500 truck doesn't have any heat.

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My Chevy Silverado 1500 truck doesn't have any heat. The heater hoses are hot, the engine is at temperature, the coolant is topped off, but no warm air flows through the vents (defrost, face vents, or floor), and we're freezing in South Dakota. Are my HVAC actuators broken? Is my control module broken? Both? Should I 'calibrate't the control module? How should I approach this problem?

Already Tried:
I felt the heater hoses, and they're hot. I cycled the control module and felt just a little heat, but not much there. I checked the fan belt routing, and it's correct. I haven't removed the control module or any actuators, so I don't know if they're ok.

Hello, do you have manual HVAC or automatic HVAC and if auto, can you control each side with seperate controls?
Customer: replied 6 years ago.
Manual (if I understand your question). I have three knobs: fan speed, heat/cold, and location (face, face/feet, feet, defrost/face, defrost). I can't control each side. There are not separate controls for each side.
Customer: replied 6 years ago.
Here is some more info: Only one heater hose is hot at the firewall. The other one is only luke warm, after the truck was driven for 30 minutes (in 20 degree temperature weather).

Ok, without doing a system scan with a scanner, there are a couple things you can do/check. You can try a recalibrate but... likely not going to work as this is normally for if repalcing the HVAC module. The module does a self calibration if an actuator is replaced. At this stage I am leaning towards a frozen/stuck /inop temp blend actuator OR the blend door is binding itself. You are lucky in that on your model and system, the actuator is easy to get to rather than most where you have to pull the entire dash. the actuator is up under ight side dash mounted on the bottom of the HVAC case. You can un bolt it, leave plugged in and watch to see if it moves when going from hot-cold. . Also look very close at it to be sure the small gear on the end is not stripped. If is does not move? one can only assume the actuator is bad. Now... it could be control module/panel but more rare and does require a scanner. Also, one you take the actuator loose from case, you can use a small screwdriver to see if the door will work back/forth manually. this is just checking to be sure door is not bound. I have seen some people in a 911 move the door by hand and insert the actuator so it holds that position all the time so you at least have heat till fixed. below are directions for actuator and recalibrate. hope it helps


  1. Remove the IP insulator.
  1. Disconnect the electrical connector (8) from the air temperature actuator (9).
  1. Remove the air temperature actuator retaining screws.
  1. Remove the air temperature actuator.


  1. Install the air temperature actuator.
  1. Install the air temperature actuator retaining screws. NOTE: Refer to Fastener Notice in Service Precautions. Tighten Tighten the screws to 1.6 N.m (14 lb in) .
  1. Connect the electrical connector (8) to the air temperature actuator (9).
  2. Install the IP insulator.


Alternative Method (w/o Scan Tool)

  1. Clear all DTCs.
  2. Place the ignition switch to the OFF position.
  3. Install the HVAC actuator.
  4. Connect all previously disconnected components.
  5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
  6. Install the HVAC/ECAS fuse.
  7. Start the vehicle.
  8. Wait 40 seconds for the HVAC control module to self-calibrate.
  9. Verify that no DTCs have set as current DTCs.
Randall C, ASE Master Tech
Category: Chevy
Satisfied Customers: 12695
Experience: ASE Master, L1, 32 years, Diagnostic / Electrical Specialist
Randall C and 2 other Chevy Specialists are ready to help you
You beat me to the punch as i was sending answer. You intially stated in the post both heater hoses were hot. If they are not, you still want to check the actuator operation first and then if ok, you may very well have bad heater core and the... the dash comes out

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