Need Help with AC/Heat not working properly

New guy here with a 2008 tacoma 4x4 trd sport double cab. just noticed when i try to turn the temperature from cold to hot, its like the duct leading to the vents is blocked. the blower is still blowing, but the forced air is NOT getting to the vents. only happens when temperature gets over midway point from cold to hot. blows just fine on cold(and with a/c on). any ideas on what is causing this, and what the solution may be? Thanks for any help.

 

The temperature control has nothing to do with where the air blows through.
It's a Tacoma... not a Chevy, you actually have a choice to run the AC on your feet if you'd like.

 

Here is a troubleshooting table from the manual. Here is the manual. The Heating and AC stuff is near the bottom.

 

I understand the temp control SHOULD have nothing to do with the airflow. However, The temp control is the one triggering this problem. Just looking for help, NOT sarcasm(Chevy?)

 

Okay... so what is happening and what is not happening?

When you have the vent control set to dash, what happens as you cycle the temp level?

When you have the vent control set to floor, what happens as you cycle the temp level?

When you have the vent control set to both, what happens as you cycle the temp level?


The place the air is blowing from should not change. The temp control only actuates the flapper that bypasses the heater core.... it should not be redirecting the airflow unless someone has reversed/crossed/paralleled the connections to the two stepper motors.

 

regardless of where the vent control is set, the problem persists. If i have the vent control set on 'dash', the air flows just fine until the temp control is turned to hot, and the air flow stops. The blower is still blowing, the air is just NOT getting to the vents. Same happens when vent control is on 'floor', air blows just fine until the temp is turned from cold to hot. same on ANY of the vent control settings, air flows just fine until the temp control is turned from cold to hot. Something is triggering this problem when the temp control is turned from cold to hot.

 

Okay, so when the blend door directs the air through the heater core, the flow is stopping.

That makes sense. It does sound like the heater core might be plugged.

 

Ideas on correcting this issue? Thanks

 

The heater core is not very accessible. Changing it requires pretty much complete disassembly of the dash.

I'm not sure what kind of tools you have access to, I'd maybe pull the blower and run a snake-type camera into the ducts to try to observe what's happening.

What's the history on the truck? Has it ever worked properly? What's the last thing that happened before it messed up?

 

I dont know the history of this truck and problem, i just purchased it four days ago. Unfortunately for me, I made the mistake of not checking the heat. Now I'm left with the task of fixing this problem. This is my first tacoma, so i'm somewhat unfamiliar with the systems of the truck. trying to learn. good idea with the camera

 

There's a lot of good information in TMW's link.
I scanned it and couldn't find anything immediately, but that's the information a dealer tech would be using.