Heater problems

Just looking for some information before I take my dash apart. The heater in my '01 Tacoma is acting up, when I turn the temperature control knob to the cold side I am still getting hot air coming through the ducts just like the heat is on, even with the AC on the air is still hot. Has anyone had this issue before? Looking to narrow the problem down to make it as painless as possible. Thanks in advance for any help.

 

I have a 98 so your 01 might be different (un-sure) but do you have that valve in the engine bay? It's a heater valve or something like that. When you switch temperature you should see it cycle back and forth. They like to leak too. Might be worth a check. I also have some HVAC controls underneath the dash that broke so I have to reach down and manually move it depending on if i want AC or heat. Luckily - I deal with it. lol

 

I believe there is a heater control valve in the engine bay of my 01, I'll check it out and see if it is working. I have a feeling I will have to do a deep dive in the dash, luckily I just need to take out the center section of the dash I believe to get to the heater controls. Summer is right around the corner so I need to get the heater turned off. Thanks for the help.

 

Your right, it's in the engine compartment (see red circle below). Here are instructions to remove that section of the dash.

 

Thanks for the help and the instructions Wsidr1. It is always a big help to have a community of people you can get helpful information from.

 

Yep, very good chance it's your heater control valve. It cuts off hot water going to your heater core when heat is set to off. It has a diaphragm inside that can get dry-rotten and crack.
Switching your heat on once or twice momentary during the summer will increase your heater control valve life.

 

That is probably a good place to start looking, it is a 19 year old truck and I have never replaced the heater control valve and I have owned it since new. Thanks for the help.

 

Did you get around to replacing the part yet? Was this a fix?

My '96 has similar issues, though maybe not as extreme as yours. AC blows cold, and "coolish" air will come out with the AC off and the lever set all the way to cool. It goes hot if I move it even slightly off of the extreme cool side. No flexibility to adjust.

 

My 02 has been doing it for a couple years. Usually you can turn it all the way up to heat and then back down to cool and it will cool for a while then go back to heat. Now its getting worse so i will repair it, cause i am to lazy to before. Three things will cause this: 1) the water control valve located on the firewall, but if it is this its not likely to ever go cold but would remain somewhere between hot and cold if you do not move the temp dial. 2) the temp control potentiometer located on the heater controls is bad, mostly like the problem if it the temp changes without you moving the dial. 3) Air mixture blend door actuator that is located on the duct work that changes the the air flow thru the heater coil or the ac evaporator.

 

I have not fixed this yet, like smithlaketaco stated I turned it all the way to hot side and back to cold and it is not blowing out hot air now but I have got to take the time to get it fixed. I think part of my problem is the air mixture blend door actuator as I can hear a noise coming from the center of the dash at times that sounds like into a motor grinding, so I will take it apart one of these days soon and fix it. I have been a bad seat belt tension sensor as well airbag light has been on for some time and I need to get that fixed also.

 

Played with mine on the ride home yesterday and this is what i found. With the temp selector all the way to the cold setting and the AC on it was blowing hot. I just pushed the knob straight in with some force and the air temp would drop to cold. I could release the selector and it would go hot again. I reproduced this a few times, and finally it stayed cold. So in short my selector temperature selector Pot (potentiometer)(rheostat) what ever you want to call it, it has many names, is bad. Time to put out a hundred bucks for a new one, but hey i live in alabama, AC is a must

 

Just an FYI for anyone else running into this problem, I finally got around to replacing the heater control valve and it fixed my problem of either having cold air with the AC on or full blast hot air if I moved the adjuster away from the coldest setting at all. We have a mix again! I used the Four Seasons brand. Other options were expensive OEM or no name Amazon ransoms.

Word of warning, there’s a wrap around hose clamp held together with a cotter pin on one side of the valve and a pinch clamp on the other. The one with the cotter pin broke right apart when I went to take the pin out and unwrap it. Probably wise to have some good old fashioned worm type hose clamps on hand if you replace this bit.