Heater issues: heat automatically directed to windshield, no matter selection?!

10/07 update for REF and possible future searchers: Finally got issues resolved. Seems @ColoradoTJ called it, well done!

Turned out to be an air mixing vent disengaged from heater box transmission? See attached photo of service dept description. All is well now, zero air is diverted to vent, no matter the temp. Its like a whole new truck!!

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'17 SR5 crewmax:

When HVAC controls are turned to full heat and console/floor vent, the controls will override to windshield vents with very little flow coming from console/floor vents. When I turn the heat to straight up halfway, full flow to console/floor as selected. Turn only heat up a little bit, and I will hear vents redirecting flow back to the windshield?

What gives?! It seems the HVAC controls are set to not allow anything over middle temp selection to the console/floor vents. If anything over middle temp is selected, the controls force flow to the windshield?

 

I'm no expert in this area, but do you have any modifications at all or ever pulled the HU or dash apart for any reason? Hopefully someone can pipe up with prior issues and a remedy in this area for you.

 

It never fails. I hear a subtle squeeking sound, like something is closing, a few minutes after I shut off the engine. I think it s that door resetting itself.

 

i can hear the blend door switch when i turn the heat down to the middle position, one click to the hot, and i hear the door move again and direct the flow to the windshield. it works, just directs the heat per the heat setting, rather than the position knob. if that makes sense.

 

I had my defrost button selected which overrides the outputs on my 17. Kind of the same symptoms. It confused me for a few days. Make sure no defrost is selected before trouble shooting...

 

Two questions for you:

1. Do you have the upgraded HVAC (with the sync button and the little LCD screen)?
2. If so - when it does this, does the LCD screen take a few for anything to show up?

 

The blend door actuator was a known issue with the fifth generation 4runners; I had to replace mine when I owned it. Sounds like this is the same issue

 

I just have the standard 3 knob HVAC.

Defrost button is not on.

It seems the door actuator is working fine. flow is diverted normally how ever I select it when the temp dial is straight up or anywhere to the cool side. Its just it seems the flow overrides to the windshield, no matter the flow selected on the dial, if the temp dial is anything more than straight up towards the heat side.


I just want hot air to blow on my face and feet when i select it!! Is that too much to ask?!! ha!

 

My first thought was that the defrost button was on - that overrides any other settings. But it would override everything no matter the temperature.
If you hear the doors moving (yes, that sound you hear after you turn off the truck is them resetting), and things are working normal until the temperature is turned up higher, then at surface level I would think it probably isn't the actuators...

Which would lead me to suspect the possibility that the AC "amplifier" (ECU) is having issues. OR, it could be a door actuator failing (just not the one you are hearing move), and that is causing the AC amplifier to move to a trouble mode and override to the defrost.

I don't have the manual controls to test with, but the reason I would check all of the different actuators first is 1) they are a lot cheaper than the amplifier and 2) if one of the actuators is failing, I have found that it causes the amplifier to do strange things.

For example, on my 2008 I did the Auto-AC climate control upgrade. Prior to me doing it, everyone that had done the mod had used their manual actuators and wiring harness and kept having issues with the AC system re-setting every time they started up the truck (temperatures would be reset, previous settings for mode/fan/etc. would all be reset, etc.). When I did the upgrade on my truck, I added the extra actuator (even though it wasn't hooked up to anything), and also swapped the wiring harness out for the one that had a terminal for the extra actuator as well. Because the amplifier was expecting to see and send power to 5 actuators instead of 4, it worked perfectly in my truck and I had no issues with resets, lost settings, etc.

Then, after about 4 years, I started having issues with the AC resetting, and also having issues with the air not coming through the right ports (I don't remember exactly which ones it was routing to, but it wasn't the ones I would select). I started checking the actuators and found that one of them had crapped out. I ordered a used replacement off ebay for $20, swapped it out, and everything worked again.

 

Thanks for posting this. I say this because I'm having the same occasional issue (and I mean REAL occasional) but I've got the automatic AC thing. It happens SO infrequently that it's damn near impossible to catch; and I was wondering if there was a way to sort of troubleshoot it.

In my case, it's a bit different - when the truck turns on, the little screen that displays the vent direction is lit up but blank for about 45 seconds....once it lights up, I can press any button I want but it still defaults to the defrost vents.

 

Are you getting luke warm or hot air from any other vents? My 2007 that I just bought last week is doing the same thing. I have found a few videos, and plan to try and fix it tomorrow after it warms up a bit.

For diag and trouble shooting with a breakdown of issues:

https://www.youtube.com/watch?v=6FB8IaEgFcE

Showing correct alignment of doors for reassembly:

https://www.youtube.com/watch?v=Yo9HTgMO2tU&list=LL&index=2

 

OP - I suggest you post this at the Ask the Mechanic thread
https://www.tundras.com/threads/ask-the-toyota-mechanic.2404/page-72#post-2146509
Dave aka @Ruggybuggy is a retired Toyota mechanic and provides excellent experience and advice to forum members.

 

I can confirm that the above videos helped to resolve my issue. I now have full function of my HVAC. My motors just needed to be re-timed because someone broke off the top retaining piece to the clip on the wiring harness side. That said, OP it wouldn't be a bad idea to get advice from a pro.

 

Nope. When it happens to me, it's only coming from the defrost vents; but it's full hot/cold air, whatever I want.

They did replace a damper...but it didn't make a difference, so they're contacting the Toyota FTS to see what the next step is.

 

did you ever get this issue resolved? I finally got mine resolved, "defroster flap not engaged to transmission". I updated my initial post with info. Hope that helps if you are still having issues.

 

I had this happen to my 2020 Tundra today. I have the LCD screen and sync and all that jazz. Went outside today at -20C and started my truck and the LCD screen didn't show anything as you described for about a minute. I figured the screen was slow because it was so cold. Then it came on and I thought all was normal. I had my heat on full because well...-20 lol. However after driving for 20 minutes my feet were still freezing. That is when I noticed that the air was only coming out of the window defrost. Did not matter what mode it was on.

I turned it all off and turned it back on...nothing. I turned the truck off and turned it back on and it was still doing it.

I have seen some horror stories of people being quoted $3,000 for the fix.

I am not happy.

 

Warranty? Keep us posted please.

 

Rog will do, I'll have to call them on Monday. I completely expect to be dicked around.

 

If you’re under 36k, it should be covered under the bumper to bumper warranty.

 

I am under that. I still expect to be dicked around lol

 

So I tried the truck today and it seems to work as normal. I am sure that Toyota will try to say it's fine and put it off until the warranty is over.

 

Can I ask a quick question as a side note? On these trucks if I turn the dial to defrost/floor or defrost setting, does the A/C compressor automatically come on? Or do I still have to manually hit the button to turn it on?

On previous trucks I've had, the floor and dash vent settings would require a push of the A/C button to get dry, conditioned air but the defrost or defrost/floor settings would kick it on automatically, for obvious reasons. Just curious how these trucks are designed to function....

 

@yosh2000 - sort of. It was 'fixed' last year (March, I believe). They replaced the servo damper subassembly, and it fixed it....until about 2 weeks ago. LOL

Trying to catch it to see if it does it again. I'm not too upset, as I don't think the issue is super widespread...but while the heat 'works', with literally every single vehicle I've ever owned, I've never had any issues with the HVAC...until the Tundra. It's the ONLY issue I've had, but given the cost of replacement, I sure hope that it doesn't persist forever. We'll have to see what happens this time.

 

Took my 2020 to Toyota today for this issue. The truck is still under warranty. Service guy called me saying the mechanic checked the codes and it turns out the battery is bad and they believe that's what's causing the heater to be stuck on window defrost only.

I refused their $350 battery and said I'd replace it myself.

Go to pick the truck up and they charged me for diagnosing the problem. $77. I asked why and he said batteries aren't covered under warranty. I said yeah I get that replacing the battery isn't under warranty but for me bringing in my truck for a heater issue and you saying it's the battery forces me to pay out of pocket for the diagnostic? I wasn't happy. Not sure if I should take it further up the line as I find that to be total BS

 

If it is the original battery it should be covered under the 3yr/36k bumper to bumper warranty and or under the battery warranty itself. I would escalate this if it were me. I hate dealers and understand the frustration. Keep us pirated.

 

The only thing under the warranty under the exclusion section that talked about batteries is this. But I believe transmitter battery is the key?

 

Are you going to escalate this and or show the dealer? I’m assuming you paid the diagnostic fee to get your truck back

 

I did pay it. I debated just grabbing the keys and saying nah I'm not paying that but then they'd likely call the cops and I am a cop in that area and then it just gets awkward lol.

Yeah I'll be making some calls. Not sure if I should be calling the dealer or someone from Toyota. Any recommendations?