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I've known something wasn't right with my Tundra's HVAC for the past few weeks and just never thought to dig into it because I've been so busy. I decided to Google my problem while stuck in traffic today and look what I found...

Heater stuck on defrost - TundraTalk.net - Toyota Tundra Discussion Forum

Unfortunately, they make no mention of a fix. The problem I am having is this. I can change fan speed, temperature in both zones, etc. but I get no air out of the vents on the instrument panel. The mode select swaps the zones on the screen, but does not change where the air flows from. The only vents working in front are the two on the top of the dash for defrosting the windows and the big one in the middle to defrost the windshield.

It is going to get really hot, really soon down here and I am praying that the "brain" of this HVAC control hasn't died on me. I have pulled the Nav head unit out several times, but I pulled the whole thing apart this evening and unplugged and re-plugged all connections to the HVAC controls and it still will not function properly. No wires were pulled loose either.

Anyone else experience this? What was the solution? Thanks!
 

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Discussion Starter #2
Anyone?
 

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Which knob did you rotate violently...the mode selector?

Anyone know where the vacuum lines are located that could potentially cause this?

Not good when a Google search only turns up TWO people in the entire country that have had this problem and neither have responded thus far as to what was repaired to fix it. My dealer's service manager has not heard of the problem yet either and is going to do some research for me.

I'm sure this is going to get VERY expensive though.
 

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Service manager has no idea. It hasn't been in the shop yet, but he started troubleshooting over the phone. Couldn't really find anything in their repair database that was an exact match but the closest referenced replacing the A/C amplifier, servo motor, and wiring harness in that order. Now tell me that makes sense...Replace the most expensive part first?!?!?

Who in the world knows what is wrong...hopefully the guy on TundraTalk.net will respond.
 

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Now tell me that makes sense...Replace the most expensive part first?!?!?
Well actually it does.
1) The AC amplifier is the easiest thing to replace.;)
2) It is the most likely to fail.:(
and...
3) It's the most expensive!:mad:
 

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I had the same problem with my 07. No heat on my feet, stuck in defrost.

Its the defrost / vent / floor mixing box. Nothing to do with the cooling (A/C) or the heater core. Its all driven by one electric motor and depends on which gear or damper door broke. I'll try and make it easy? Under the radio and behind the middle hump blank off panel on the floor is the mixing box. There's 4 dampers, 1 motor and a **** load of plastic gears.

4 dampers = defrost - vent - front floor - rear floor
1 motor up above the gas pedal.
1 plastic duct feeding passenger seat
1 plastic duct feeding drivers seat
2 plastic ducts feeding rear floor heat
Can't see the ducts for the vent or defrost.


Best way is to run the truck, put the fan on low, switch from defrost to heat and listen to any noise that may happen. I had to have my women on the passenger seat while I was under the dash listening and watching.

To make a long story short I heard and saw everything working but no heat to the floor. I pulled the duct off the drivers side and could see the damper not working. I stuck my finger in there and it opened up. Never to close again.

Good luck, keep us posted....
 

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Discussion Starter #11
I had the same problem with my 07. No heat on my feet, stuck in defrost.

Its the defrost / vent / floor mixing box. Nothing to do with the cooling (A/C) or the heater core. Its all driven by one electric motor and depends on which gear or damper door broke. I'll try and make it easy? Under the radio and behind the middle hump blank off panel on the floor is the mixing box. There's 4 dampers, 1 motor and a **** load of plastic gears.

4 dampers = defrost - vent - front floor - rear floor
1 motor up above the gas pedal.
1 plastic duct feeding passenger seat
1 plastic duct feeding drivers seat
2 plastic ducts feeding rear floor heat
Can't see the ducts for the vent or defrost.


Best way is to run the truck, put the fan on low, switch from defrost to heat and listen to any noise that may happen. I had to have my women on the passenger seat while I was under the dash listening and watching.

To make a long story short I heard and saw everything working but no heat to the floor. I pulled the duct off the drivers side and could see the damper not working. I stuck my finger in there and it opened up. Never to close again.

Good luck, keep us posted....

So did you replace a part? Is everything functioning normal now? One more...could you help me out a little bit more on where exactly it is located...I'm not following you on the location. Thank you SOOO much for responding.

Matt
 

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Discussion Starter #12
Went down to the garage and tinkered with it for a few minutes and saw exactly what you are talking about but I can't access the motor/damper that controls the instrument panel vents from the driver's floorboard (disassembled the console but got stuck and didn't know where to go from there to remove everything). I wonder if I need a new damper/motor assembly? Are they sold as individual units or do you have to buy the entire "black box" that's down there (dear god that would be EXPENSIVE for the whole unit)?

At least I think I now know where the failure is. I may just breakdown and go to the dealer Saturday morning and call them tomorrow and get a motor/damper on order (if sold individually) just in case one is needed. Its getting really hot down here....
 

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Went down to the garage and tinkered with it for a few minutes and saw exactly what you are talking about but I can't access the motor/damper that controls the instrument panel vents from the driver's floorboard (disassembled the console but got stuck and didn't know where to go from there to remove everything). I wonder if I need a new damper/motor assembly? Are they sold as individual units or do you have to buy the entire "black box" that's down there (dear god that would be EXPENSIVE for the whole unit)?

At least I think I now know where the failure is. I may just breakdown and go to the dealer Saturday morning and call them tomorrow and get a motor/damper on order (if sold individually) just in case one is needed. Its getting really hot down here....
My first question would be is the motor stroking when you switch the control from defrost to heat? On mine it was and could see the large plastic gear move and hear the floor damper click, but not open. It doesn't move much to switch the dampers. On yours it could be a different damper that jambed or if the motor isn't stroking need to test for power / electrical problem or motor failure.

To answer your other question with the floor damper open all the time defrost / vent & floor still works as the air takes the path of least resistance. When its switched on defrost and or vent some air still comes out of the drivers floor vent but not much.

I had the exact opposite happen on mine, 30 below with no heat blowing on my feet. Boy my feet good cold.

Ya it looks expensive and jambed in there good.

Maybe someone can post how to properly remove the mixing box or disassemble the dash. I always end up breaking some plastic tabs or something. Might be better off having the dealer do it?

Good luck and keep us posted.
 

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I have a PDF here for removal off the AC unit but I don't think you even want to know!!
It says you have remove the dash, steering column, and dash support frame just to get to it.
 

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I have a PDF here for removal off the AC unit but I don't think you even want to know!!
It says you have remove the dash, steering column, and dash support frame just to get to it.
Please post this as soon as possible...I'm talking to the dealer this morning about a timeline for this because I can't be without my truck for a week. Thanks!!!
 

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Dear god...You've got to be kidding me...Why is it that Toyota's primary failures are ridiculously expensive endeavors such as this, the Air Induction Pumps, etc. This is ridiculous!!! I am SERIOUSLY doubting Toyota's QA/QC and am going to call Toyota Corporate in a minute to vent my frutstration!!!

Thanks for posting this.
 

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OK, This is from TIS so I'm sure the dealer already has it.;)
WOW, very nice. Wonder how many hours they give you to change it?

I guess thats why everyone is saying is it an electrical or mechanical problem. I'd say you have to make absolutely sure its the problem.

I know my 03 Dodge was the same way, except the mechanic left the instrument panel on the roof and it got rained on....The poor truck was never the same. Thats why I went with the Tundra
 

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Discussion Starter #20
Dropped off today...I'm crossing my fingers and praying they don't screw up all my custom electronics. I left a list of everything custom installed, including where and what it is, taped to the nav unit. I hope the tech actually reviews it...
 
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