A/C blowing through wrong vent

[structures]

I have a 03 Z71 with 76k mi. Around 40k miles I heard a clicking noise coming from under the dash and dismissed it for quite some time. Then after a while I noticed if I took the vent control knob and turned it one click back from full top vents, the clicking noise went away. So I just left it there and drove for some time (a couple of years now). About a week ago I was leaving work and started the truck turned on the A/C full blast and I couldn't get the top vents to blow air. It was like the control gate would only go from floor vents to de-frost vents, no top vents. It's an intermittent problem but I believe it has to do with either the control box where the knob is or a relay on the gate has a bad solder joint. Which may be what the clicking noise is.

Anybody have this issue before? How did you fix it?

[clinebarger]

Originally Posted by structures

I have a 03 Z71 with 76k mi. Around 40k miles I heard a clicking noise coming from under the dash and dismissed it for quite some time. Then after a while I noticed if I took the vent control knob and turned it one click back from full top vents, the clicking noise went away. So I just left it there and drove for some time (a couple of years now). About a week ago I was leaving work and started the truck turned on the A/C full blast and I couldn't get the top vents to blow air. It was like the control gate would only go from floor vents to de-frost vents, no top vents. It's an intermittent problem but I believe it has to do with either the control box where the knob is or a relay on the gate has a bad solder joint. Which may be what the clicking noise is.

Anybody have this issue before? How did you fix it?

Release the stops on the glove dox door & let the door all the way down, There will be a opening in the dash. You will be able to see the HVAC harness (pictured). Check the harness to see if the metal dash support has worn into some of the wires. Check this first & get back to me.

If this is not the problem you need to retreive the codes from the HVAC module. A Tech 2 scan tool is the only one i know of that can do this, even my overpriced Snap-on scan tool cant.

[structures]

harness looks good.

[truckdude239]

blend door actuator probably went out

[clinebarger]

Originally Posted by structures

harness looks good.

I need codes to help you, Unless you just want a guess?....When you put the "A/C full blast" you mean you hit the recirculate button, then it defaulted to defrost/floor only? If so you chould have a bad recirculation door actuator motor.

[structures]

Originally Posted by clinebarger

I need codes to help you, Unless you just want a guess?....When you put the "A/C full blast" you mean you hit the recirculate button, then it defaulted to defrost/floor only? If so you chould have a bad recirculation door actuator motor.

Yeah these intermittent problems are hard to guess at. When you say codes. You mean from the OBD port? I don't know anybody with a tech II and I looked at buying one years ago, but I think it was like $2000 so I passed.

So what happens is, I start the truck with the vent control knob on the top vent setting, A/C and recirc are already on. Almost immediately the air blowing transfers from the top vents to defrost. Even though the selector knob is still on the top vents. It's happened twice now. The only way to get it to go back to normal is to pull over turn off the engine and restart the engine. This last time coming home from work I couldn't get it to work I pulled over twice and tried turning it off and on, but couldn't get the air to stay blowing thru the top vent. It just transitioned to the defrost vents on its own. What's weird is that if I turn the vent knob to lower vents while this problem is going on I can get the air to transfer down. I drove home with cold air blowing on the windshield and my feet. Let me tell you when it's 102 outside that doesn't keep you very cool!

[structures]

Originally Posted by truckdude239

blend door actuator probably went out

or is going out?

what about the clicking from the drivers side is that some kind of relay or something

[structures]

Originally Posted by clinebarger

Release the stops on the glove dox door & let the door all the way down

hey by the way that's a pretty slick trick I never knew about.

[bighaas79]

I've had the plastic gears inside the actuator motors get stripped and make that clicking noise.