HVAC Issues

I’ll try to describe this without taking up your whole evening.

‘19 Platinum Crewmax. My truck is blowing hot air on the driver’s side and rear vents all the time. All. The. Time. I have not been using the A/C; it’s been cool enough outside. I’ll get out of my truck and turn it off with my settings synced around 68 or so. I come back to my truck later, start it up, and my controls are unavailable. The “auto” light is actually lit up (I never use auto). I can’t change any setting on it for 20-30 seconds.

Then, the auto light goes off by itself and I turn the fan speed up to turn it on. The A/C light is on every time.

No matter what I set the temperature to, driver’s side blows hot. The 2 rear vents are blowing crazy hot.

I'm finding some research question a servo motor? But my stealership, I mean dealership, spent about 3 hours and couldn’t find any issue other than claiming I’m slightly low on refrigerant. But even on a cold day outside, my truck’s temp on low is still blowing hot.
Anyone run into something like this before?

 

Sounds like a blend door issue

 

Is that en electrical deal or mechanical? I just find it weird how the electronics/brains of my HVAC keep resetting.

 

I’m having the same problem. The blend door servo keeps popping up as the culprit. I can actually hear mine pop a few seconds after I turn the truck off. Prior to it failing I could hear the door shut.

 

Blend door and servos is definitely where I would start. Last summer I took a pretty deep dive into understanding the AC system.

A cheap digital thermometer gun helps. If you are getting cold air out of at least one side more than likely refrigerant levels and compressor operation is fine.

Few things to check quickly, is the AC clutch on the front of the compressor locking in when AC on? If you have Techstream you can look in the AC ecu (I think) and see the thermister value in real time. This is a temperature reading on the cold side of the AC coil. If it is significantly lower than ambient temp on a hot day in like 60 degree range, the AC is making cold air no problems it’s not just getting delivered to the vents.

The HVAC unit is under the dash below the radio. It has 4-5 servos that control which vents air blows out of abs the temperatures for each side of you have dual climate control. I believe you do on a platinum. All of the servos have a unique part number and are not interchangeable as they all work on the LIN bus and each responses only to its specific communication messages from the AC amplifier (ecu).

It’s really kind of a pain to get to the servos but some good videos on YouTube. The system is pretty complicated setup of gears and servos. If the servos and gears are moving but no change in temp still the internal blend door is broken. This is worst case because the entire dash has to come out to get inside to the blend door.

I would start by making sure the AC system is making cold air first. Then locate the drivers side blend door and see if it’s actually moving. In some situations the gears get misaligned, jammed or a tooth broken off. You can replaced gears and servos with the unit still in the truck. Blend doors and other internal stuff will require dash removal.

This is one of the better videos to understand the servos. https://youtu.be/_udGpW7QKHk

Some servos control temperature other control vent position.

 

Also the AC amp is the ecu that controls this. It is under the glove box passenger side. It can reset when it’s not happy or doesn’t see communication with a servo motor ect.

Could be worth a quick check to make sure all the servo motor connectors are plugged in tight and you have no broken wires ect.

Techstream might even show error codes for the AC amp which could further help isolate the problem.

 

Thank you for the input. I don’t have any of that software at this point. I’ll give the dealer another chance to see if they can find it since it’s under warranty. I just dread them taking my dash apart. I need to get it figured out and fixed before weather changes to hot!!

 

Update: they did find out that the servo seems to be the culprit. Tech said the doors aren’t opening and closing like they’re supposed to. Part is ordered - hopefully I can get it in there soon.

Would that part also affect the electrical delay in being able to operate my HVAC controls? It’s close to 30 seconds after starting my truck before it even lets me operate my HVAC controls at all.

 

Yes I have heard if the AC amp (ecu) isn’t happy with all servo motors, it creates a 30 second or so delay. I think on startup it sends signals to detect working servos. The delay is it trying to establish communication before it eventually gives up.

I switched to digital AC in my truck. I am using 4 servos but apparently the digital AC ones need 5 servos. Since mine is missing a servo I have a 30 second delay and it never remembers previous settings. Almost like it completely resets every time. It takes several seconds for the display to even light up after key on.

Other users have reported adding the 5th servo fixes his, making the AC amp happy with all working servos.

 

If you’re still in the warranty phase let the dealer figure it out. My 2019 only has 21k miles. I’m covered until august. Otherwise good luck getting it fixed, I have no idea.

 

Are you still under warranty? I had a blend door (not just the servo) that was defective from the factory - the face vents always had air coming through. The entire dash had to come off for the replacement.

 

Oof. I have a similar issue. The only time the dash vents don't blow air is if the front defrost/defog is engaged. Throw it to only blow on the feet, and it still blows in your face. Been that way since I bought it, and I mentioned it at a service, and was told they'd have to dismantle the dash to get investigate. Didn't have time to wait that day, and I'm so gun shy about having the dash torn down. My luck, some idiot will break clips and hide it so I won't know until it starts creaking or rattling 10 miles past warranty.

 

I had similar concerns but the dash was solid afterwards. Get it done under warranty otherwise the cost will be ridiculous.

 

How much air? Mine always has some air coming out even when the floor only vent is opened. I just close the vents.

 

I'm having the exact same problem on my 18' Tundra and debating on taking it to the stealership or a shop. Since your dealership has the part on order, will they have to remove your dash to have it replaced? My warranty just expired Aug of 21' so think I'm screwed!

 

This gives me some hope!

Yes, still under warranty. Its a certified pre-owned, ‘19 with 50k.

I share that concern, but at this point, I’m willing to accept the risk. This problem is driving me insane!

Some amount of dash and lower middle console have to come out (from my understanding).

 

I had my blend door replaced - the entire dash came out.

 

Dang! Ok well thanks for the input. Last question, cause I need to take care of this in the morning: Who would y’all trust more to do the work correctly? Dealership or local (does it all) auto repair shop?

 

The location doesn't matter. It's the person doing the work that does. If you know the techs at the dealership and trust them, I'd go there just to keep it all square with OEM parts/clips if they break any, but if you have a buddy at a different shop and you're outside warranty, go for bad.

 

Yeah, I was under the impression this was normal.

 

Final update!

It ended up being a bad servo motor. Thankfully it was covered under the warranty or it was going to be about $900. Ooof. Thanks everyone for the input.

 

Another Final Update Here!!!

After debating whether to take into a local repair shop I opted to go with my local dealership. The good news is that they replaced the bad SERVO and got the job done right - everything was put back into place and nothing rattles! The bad news is that I was out of warranty and out $900 clams!

This thread helped a lot because I was able to push back on the dealer when they were claiming that the "amplifier" was bad and responsible for the 30 second delay after starting up truck.

Thanks for the input folks!

 

Glad yours got fixed up too! Unfortunate about being out of warranty, but at least you can have cool air in your face again! Cheers

 

This was - and is mad, the issue I'm having. It's literally the only issue I've had with my truck. It doesn't happen all the time, but yeah, what I've seen above is the exact issue I have had. System tries to reach out to all servos upon start up and if it finds them, great; if not, it tries to reach out to them, and eventually stops and puts the system into 'safety' mode, where it's only blowing on defrost vents. The 'fix' for mine a year ago or so was supposedly the 'servo damper subassembly.' I'm not quite sure how, as when it works, it works fantastic, and there has never been any issue switching vents, no clicking/scraping sounds, etc.