Heater starts blowing cooler air

Hey all, just wanting to pick your minds. (I know, very dangerous thing to do here....)
My truck is a 2017 DCSB Sport with about 48,000 miles. A couple nights ago I was driving home and after 20 miles or so realized my heater wasn’t blowing very warm. Fan was on 2 clicks and temp set at 73 (normal setting for me) Outside temp in low 40’s. Was driving interstate speed. I turned the temp up a couple degrees but it didnt seem to make a difference. Needle on the temp gauge was as it normally is, no fluctuations.
Checked it the next day driving around town, no problems, blew nice and warm all day.
Yesterday went out of town again, and on the way home it felt like it was blowing colder again.
Any thoughts on what may be happening other than I’m female and over 60 LOL...
Out of factory warranty but do have an extended warranty, but wondering if dealership could replicate..... Thanks....

 

Check coolant level first

 

Engine coolant flows through something called a heater core (it looks like a small radiator). To heat the interior of a car, a fan blows air over/through the heater core, heating up the air, and then discharging it to the vent system. If you're not getting hot air, that means there is no heat in the heater core; which means there is likely not any coolant flowing through it.

The heater core is most often located on the passenger side behind the glove box. Check the carpet/floor of your truck to see if it is wet. I had a Jeep once and the heater core blew and release all the coolant into the passenger foot well. I didn't notice until the engine hot light came on. Check coolant level when you check your carpet.

Alternatively, the line to the core could be plugged if you find you have adequate coolant levels.

 

Oh also check cabin filter! I doubt it's clogged but it's free and easy.
If you want to crawl up under the dash (usually where it is, but I've never checked one on a Tacoma) put a temp gun to the inlet and outlet of the heater core. If your HC is hot, you most likely have blend door, and/or climate control issue, and will most likely want to seek a good tech or dealer. If one end is hot, and the other not so much, good chance you have a clog, but I don't hear of those much around here, that was a Jeep thing.

 

I've noticed that my wife's '19 Corolla does this at times. I poked around some forums and determined it was normal.

In my old '15 Taco it just keeps blowing air set at whatever temp the dial is turned to.

But these newer systems seem to sense when the cabin has reached the set temp and begin to draw back some...even when not in "auto".

 

Climate control, sounds like it's working as designed. Increase the temp setting and see if it blows warmer air.

 

I am a bit familiar with mechanics and how vehicles work, so understand about heater cores. No fluid on the passenger side, and will check the coolant level. Just had a normal service recently so would like to think that was checked...but it was at the dealership LOL.

 

The models with the dual auto climate control dont keep blowing hot air continously like the standard version. They regulate the cabin temparature based on what ever temp.you set it on. Once it reaches that setting it just maintains it much like the thermostat on your house furnace.

 

I’ve had the truck 2 years and driven it almost 30,000 miles and never noticed it doing that before. Turning the temp warmer did not make the output that much warmer in correspondence. Thats what caught my attention....

 

First, do you have Auto climate control? If you do and the auto light is not on, the system will still control temperature to the set point ( you set 73°F ). The system will maintain fan speed at the set speed ( 2 bars ). I have found that this will eventually start blowing quite cool to maintain interior temperature, even engaging the A/C.

If you have the auto engaged at the same set point, then the system will control fan speed and temperature to control temperature. I find auto mode has better control overall.

 

If the Automatic Climate Controls is set to Auto it will either blow warm or cold in order to maintain the set temp.

 

For those of you who suggested check coolant level, I did and was surprised it was low, catch bucket was about empty. Topped it off with approved coolant. Will check it again next time I drive it. Have not noticed a coolant smell, park on gravel pad at home so haven't noticed a leak, but will be more vigilant now......

 

While my 2015 doesn't have an auto temp setting, my Honda does. What I noticed very early on was if I set it to ''auto temp,'' once it came to temp, the air from the vent cooled considerably and increased fogging and windscreen icing was increased. Just went back to max temp on the output and now manually adjust the blower speed as needed and I like it much better as it does a far better job of both demisting and heating the cabin. It also probably reduces wear and tear on the actual blower and controls because the blower can run at a slower speed to keep up with outside temps and it's no longer always adjusting blend doors to try to keep cabin temps withing the range needed.

 

Heat will probably work fine now, keep checking, as you may have to add more if it ran really low.
Next question is; where did the coolant go?

What year and how many miles? I wouldn't think anyone has 3rd gen yet with enough miles to act up. Work aside of course.
Ever had the coolant system flushed? If so, Maybe they didn't get the air out, or top off all the way.

 

2017 w/under 50,000 miles. Recent service was just oil change and tire rotation. And yeah, makes me wonder where it went.
I did have to have my truck towed in a couple times for engine shutting off and when restarted wouldn’t run, ended up being a bad ecu, so nothing “mechanical “ that would have required anything done to the coolant system.

 

I do have auto control but I run it on manual.

 

This^^^needs further investigation. Unlikely for such a new truck to have coolant loss. Top it up & keep a vigil eye on it. If loss continues, and you can't confirm a leak, you may have bigger problems.

 

Yep, thats my plan... thanks!