Flashing arrows on climate control

[Jim Dumpster]

I have a 93 with a/c. After getting the radiator, block, and heater core flushed, the temp selector just flashes arrows on my climate control unit. Swapped the unit out with a working one from a 92, same flashing arrows. What’s going on with my truck?

 

[evilunclegrimace]

Low A/C charge?

 

[FrankieD61]

I have a 93 with a/c. After getting the radiator, block, and heater core flushed, the temp selector just flashes arrows on my climate control unit. Swapped the unit out with a working one from a 92, same flashing arrows. What’s going on with my truck?

Check your blend door actuators. My truck had the same issue. Turned out to be broken blend door actuators.

When you go key-on engine off, do you hear a repetitious clicking or cluncking sound? If so, that would be a blend door actuator.

 

[Jim Dumpster]

Check your blend door actuators. My truck had the same issue. Turned out to be broken blend door actuators.

When you go key-on engine off, do you hear a repetitious clicking or cluncking sound? If so, that would be a blend door actuator.

So I don’t hear any clicking. I pulled the main actuator that goes behind the center dash. I tested it with a 9V battery and was able to make it turn both directions (swapping - and +).

 

[FrankieD61]

Good test. There are two other blend doors recirc blend door; located in the passenger foot well area. Attached is a picture, the circle in red is the one I'm referencing.

Then you have the mode blend door; located in the driver's side footwell, near the gas pedal, pretty easy to get too. Circled in blue in the photo.

Pull those and see what you get. Also, keep in mind, they when you pull these and apply voltage to them, there is no load such as the blend door on them, so they may work flawlessly. But when you reconnect them, the load from the blend door is enough that the gears will bind (from wear and age) and the HVAC control module will lose communication with the blend door(s) and it will go into trouble mode (the flashing arrows).

 

[FrankieD61]

Also, keep in mind, this may not even be the issue. It's just an easy check you can do before you start ripping into the expensive stuff, like AC.