Heater Blowing Cold

Why would my heater be blowing cold air even after my truck runs down the highway for 22 miles going to work? It blows warm while moving down the road but as soon a s i get off the road it goes back to blowing cold air. Thermostat??

It has been doing this since i got the truck back in March but in Texas we dont use the heater much from March to October. Well that time of year is quickly approaching so i need to get it addressed. What do i need to look into?

 

Is the temperature gauge showing that it is getting up to mid scale ( normal range)? If so it probably isn't the thermostat.

It could be the blend servo that controls the air flow between hot and cold air. Is your coolant level low?

 

My temp guage is running in the same spot it always has, about middle ways up.

i have not checked coolant level in about a month but last i checked it was good. It was doing the same thing at that time.

Could the thermostat be stuck open and that be what is causing this issue?

 

I'd consider replacing the thermostat.

 

Burp the coolant system by running your engine up to temp with the cap off the radiator. Make sure there's coolant in the overflow, and this will get any air out of the system, especially if you see the overflow sucking fluid in. Run it until no more air bubbles come out of the radiator cap area, then replace the cap. Air pockets in the cooling system do funny things, but you'd usually see an occasional overheat status.

Change your thermostat. It's an easy fix anyways.

Maybe the door in your ducts that goes back and forth when you choose a/c or heat is getting hung. Like mentioned in an earlier post, maybe it's the servo getting stuck or the flap literally is clogged with debris. I don't know where it is in the system, but might be worth checking into if you check all of the above and don't get any improvement.

Last but not least, make sure that the shop or someone didn't bypass the heating coil by re-routing a hose. That's an old trick to stop leaky heater coils, but this is very unlikely to be your case. Still worth checking. Also check that there's no kink in the heater hoses running to the coil, but there should be enough pressure in your cooling system to keep any kinks out of those lines.

 

If the temperature gage is showing correctly then it probably is not the thermostat. Consider something like the temperature control valve that lets the hot water into the heater radiator first. While running fast enough hot water gets through, but while going slow it doesn't.

 

This is true. I've noticed that when I start up my truck and let it idle but don't drive anywhere, the truck gets up to temperature but the heater never blows warm. Start driving and it blows hot very quickly.

But in OP's situation, he just drove 22 miles but then the heater went cold quickly when he slowed down or stopped. That heater core should have enough heat in it to blow hot/warm for quite a few minutes after stopping while the engine is still running. Maybe in super cold temps that would be different, but this time of year unless you're in Alaska, it should stay warm for quite a few minutes.

 

Can't say you are wrong. It will be interesting to hear what the problem really is.

 

if you figure anything out let me know Ive got the same issue

 

I have burped the radiator twice with no luck. Next I'm going to replace thermostat and flush system

 

I have had this very same issue with a Chevy Silverado I used to have. That truck was much older than yours though. mine was caused by corrosion inside the heater core and after a back flush everything worked fine again. I believe the mechanic just reversed the hoses going to the heater core and ran it for a few minutes and then flushed the radiator and then put new coolant in. That doesn't seem like it would be an issue with an '09 though. Mine was about 10 or 12 years old at the time. If you are going to flush the radiator anyway, you might as swap the hoses and back flush the heater core.
I live in the northeast and even if I run my AC with the heat settings on hot I still get hot air, so I don't know about the blend door. On my Silverado if I switched the AC on and off I could hear the door opening and closing, but not sure if you will hear it on a Taco. But if you get your ears down low on the passenger side and have someone turn the AC on and off with some fan going you should hear it opening and closing.

Hope this helps and keep us posted.

 

I have not flushed system yet because its been too cold. So while i have had idle time not having heat i have done more reading on this subject.

Someone mentioned in a post something about the heater core lines going into the firewall so i checked them. The top line gets warm rather quickly but the bottom line does not. Could that be a clue to a clogged heater core?

It is going to warm up this week from the high 30's to low 60's by friday so i will have time to play with this and figure it out hopefully, but 22 degrees this morning going to work with very lil heat was not all that enjoyable...

 

My 98 Tacoma blows hot air not matter what...idle...drivin...the heat knob clicks really bad like its skippin gears...check the radiator level...but the cable to the cable isn’t connected to the cable arm...and even when u pull on the cable it doesn’t move...but under the dash I can manually move it and I can hear the door open and close...any ideas???

 

If one hose is hot and the other isn't, your heater core is most likely restricted or plugged. I'd pinch the hoses, remove them from the fittings, and flush the core with a garden hose in both directions. That should fix it if it isn't plugged up too bad, probably should flush your cooling system too if flushing the core solves your heat problem.

 

I'm not familiar with how the heater controls work on a 1st gen, try posting in the 1st gen forum I'm sure someone there can help.

 

The heater core works on a circulatory system meaning the hot fluid goes in through the
core and back to the engine, then radiator after being reheated again and pass back through the core.
The blend door separates the cool air from the A/C --- and hot air from the heater core.
Thats why when set to the middle section of hot and cold the temp will be more equal.
Not too hot and not too cold.
Lines going to the core = hot --- And the line coming from the core = cold ---- Heater core plugged.