Heater blows cold air :(

Howdy! I was driving my truck through the mountains last night and I tried to turn on the heater but it only blew ice cold air as if the Cold AC was on, despite working two hours earlier. I am almost out of ideas of what it could be but I will list everything that I inspected to help narrow it down. Its a 2020 trd off-road for reference

-the thermostat is solid because my operating temp is normal
-it is not overheating either so my water pump is good.
-all fuses under the hood and dash are normal and healthy
-my coolant in both the radiator and reservoir is at full levels when the car is cold and also at operating temp
-I can audibly hear the heater door in the dash open and close when I adjust the temp when the car is in accessory mode
- both hoses coming out of the firewall on the driver's side are hot and of equal temperature when measured after the truck has been running
-it is a 2020 so I don't think it has a heater control valve so that's not it
- and I burped the radiator with the cap off and let it run for 15 minutes in the driveway

I am absolutely out of ideas. Any help out there?

 

Warranty!!!

 

I’m in the same boat! Took a road trip up and down CA this past weekend around 1k miles. About 1 hour from my house the heater went out on me too. Inspected literally everything you listed as well. Mines a 2018 out of warranty though :/

 

Heater core clogged up? Usually happens when there’s too much rust.

 

There's usually a bypass valve that shuts the flow of coolant to the core, when the AC is on. Wonder if that's failed shut some how.

 

Sounds stupid, but double check to see that your ac switch isn’t on

 

The plastic pipe at the back of the engine can crack and leak, repair cost is over $1000. A small crack can let air into the heater even without a visible loss of coolant. I had no heat without any visible loss of coolant so I decided to put in two containers of Subaru coolant conditioner which is actually a leak sealer. It solved my heat problem. Unfortunately, the problem showed up after my warranty expired. I also do not know how long this fix will last...

 

Oooo, that's another good one!

 

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What about critters like mice or chipmunks invading your heater core/ducts and building themselves a nest?
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I’ve recently ran into the same problem. I drove about an hour or so to go pick up my son, sat for about 5 min with truck running waiting on him and then when I went to head out about 5 min into the drive it was blowing cold. Glad I’m not the only one. I’m going to schedule a service appointment this week. If you get an update prior to when I do I would like to see what they say.

 

What was the fix? My heat just went out on my 2018 with no obvious issues like the others here.

 

Well after more research and a little luck, my heater issue turned out to be a stuck blend door. When I finally got it to work (moving the switch while banging the dash) there was a pretty loud clunk and the hot air was freed. I’m not sure if this will be a reoccurring thing but at least it not a coolant issue.

 

Usually that is a sign that hot coolant is flowing and thus its a vent/blend door issue...which is usually the cause. There must be a bind somewhere.