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Chevrolet Silverado 1999-Present: HVAC Diagnostic

Nobody likes driving in an oven or a freezer. Take back control of your Chevrolet Silverado's heating and air conditioning with these helpful instructions.

By Jared Hammond - June 23, 2015
Contributors: jcdm327, thedogg7

This article applies to the Chevrolet Silverado (1999-Present).

Does your Silverado blow hot air on one side and cold air on the other? If you have dual zone controls you may have run into this problem before. There is a way to fix this if you're patient and willing to troubleshoot your way through it. Below are a few different solutions that may just help you take back control of the HVAC system.

Step 1 – Recalibrate the HVAC

If you've noticed the control issues happening after disconnecting the battery or having repair work done, then the quickest fix is to recalibrate the HVAC.

  • Turn the ignition off.
  • Find the three HVAC fuses; Two are under the hood and one is in the cab fuse box.
  • Turn the AC and heater switches to the off position, and turn the temperature controls to the coldest setting.
  • Set the HVAC to automatic.
  • Plug in the fuses.
  • Start the engine and let it run for five minutes.
  • The HVAC should readjust automatically.
Figure 1. Pull and reinsert the fuses for the HVAC before starting the truck.

If this didn't work for you try Step 2.

Step 2 – Replace the blend door actuator

If it seems like one side is stuck at one temperature only, it could mean the blend door actuator is no longer working. The actuator turns a door to switch between warm and cold air, but there are multiple actuators in your truck. To figure out which one isn't working shut off the truck and turn the fans off. Then listen carefully when you turn the key as you should hear the actuators click to life. If one of them doesn't click it's probably not working. Note that the replacing the blend door actuator is a very complex process and it requires you to work in a very tight area. Below is how you replace an actuator;

  • Disconnect the negative lead on your truck's battery.
  • Remove the panel under the driver side's dash board (For passenger actuator remove the panel under the glove box).
  • The actuators are mounted near the HVAC controller.
  • Pry off the electrical harness plugged into the actuator.
  • Unscrew the mounting screws and remove the actuator.
  • Install your new actuator and tighten it down with the mounting screws.
  • Plug in the electrical harness.
  • Now set the fan and heater controls to off and the temperature controls to the coldest setting.
  • Reconnect the battery, turn the key and listen for the actuator to click. Wait five minutes then test the controls to see if it worked.
Figure 2. Blend door actuator with a cracked gear.

If this didn't work try Step 3.

Step 3 – Replace the HVAC controller

If your controls still aren't responding and nothing is wrong with the blend door actuator then the controller itself needs to be replaced.

  • Lower the steering wheel and pry off the paneling around the driver's side dash, the HVAC controller and the radio.
  • Unscrew the bolts on either side of the HVAC controller, push in the clips, and then pull it out.
  • Disconnect the electrical harnesses.
  • Connect the new HVAC controller and slide it into the housing.
  • Tighten the screws and reattach the paneling.
  • Start the truck and test it out.
Figure 3. HVAC control module.

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