AC won't go off with heat on, won't blow warm air

So I just sold my 07 and picked up a 2010 trd sport a month ago. Within the first week we had a cool rainy day and I went to switch on some heat and the AC would stay lit no matter the flow settings (feet, dash, combo, or defrost). After several miles and much fiddling the AC light went off and all seemed to function normally. I thought perhaps there was a humidistat that monitored in cabin moisture and mandated AC to help dry the air.
Anyway for a few weeks all has been fine, but mostly ambient weather and temps but cool and warm dial seemed perfectly normal and functional.
So tonight after work it was rainy and temps dropped into 40s. As soon as I started the truck I switched the dial to full warm and fan to low and foot setting and the recirc and AC were both activated. I pushed recirc off no problem but AC button stayed lit. I continued my 20 mile drive home fiddling with buttons and settings, even holding the AC button in for several seconds and it would not go off.
Also the system continued to blow cool air. I've searched many HVAC threads and read through my owners manual and no solutions.
I pulled the AC fuse out and went for a drive and still could not get warm air flowing.
Any suggestions yall?

 

Bump

 

40 views? Bueller, Bueller?

Ok I have a theory. Mechanically the system is stuck on the max cold setting thus keeping AC activated..???

 

The AC being on and the air temperature may be unrelated. AC compressor runs with heat in order to dry out the air and a fail safe for componants... I.e. keep the compressor lubricated for the 5 months in fall winter when mosy folks won't use it.

While the AC runs with heat on, usually the cold air isn't circulated because many vehicles have a "trap door" that acts as a valve allowing the preferred air temp to get to the cabin... that could be an issue for your case?

You didn't mention how cold the air is. Is it ambient outside temperature cool, or is it COLD AC air?

Sorry I couldn't be more help.

FYI I would put that AC fuse back so you aren't turning the AC compressor pully without power (lubricant). You'll create an expensive issue down the line.

 

Yeah the trap door not functioning properly is what I was thinking too mechanically. Do think its accessible to take a look at?
Thanks Jordan, appreciate your input.
It was hard to tell air temp. I did attempt to switch back and forth with my hand over a vent to try and detect "air conditioned" vs outside air and no big difference.

 

I'm gonna drive my 20 yr old Toyota to work that has 300,000 miles on it and (knock on wood), never has anything go wrong lol.

 

geeez, I keep searching similar threads and many have NO responses LOL. You can get a bajillion answers on issues concerning "what is best lift kit.....", but nobody wants to chime in on HVAC issues. Understandably so.............

 

My dad had to take in his 08 tundra a while back to get the control box replaced because the mix knob would not work. It could be the controller rather than the trap door.

 

Ya I considered that. In fact my dad also has a 10Taco and considering doing a quick swap to see if that cures it

 

Ok swapped out the HVAC control panel from an identical 10 Taco and didn't cure it or change any of the symptoms. First facking cold day of the year and bam, no heater. WTH is up? I buy Toyota exactly so I don't have to deal with this stupid kinda shit............

 

Any other ideas?. Bump

 

I thought there was a problem with certain year Tacoma's with the mix door insulation foam. Basically the glue holding the foam on sucks, the foam pops off and blocks the mix door from changing to either hot or cold, it stays one or the other.

Also the servo motor for the mix door might be fucked up. That's easier to get to. For the mix door you have to rip out the whole dash. The mixing area is directly behind the center console/center dash.

Edit, the TSB is for 07-09's see thread here http://www.tacomaworld.com/forum/2nd-gen-tacomas/131817-tacoma-heat-blend-door.html

Actuator servo thread http://www.tacomaworld.com/forum/2nd-gen-tacomas/247443-08-c-air-door-actuator-servo-problem.html

 

Thanks so much Smith I'll read up.

 

Crap, nothing seems to fit the picture here.
I even read through the tsb "decreased air flow from HVAC vent", Adobe file...

 

Went out to the garage to listen for the sound of mixer servo motor and it started working correctly. Went for a drive and it warmed up. Will continue to monitor....

 

Check the terminals on the plugs......(both male & female ends).

I had a weird situation occur where my truck wouldn't start (had mysterious clicking noises in the dash). After jumping it and having the charging system checked to be OK, my A/C wasn't getting cold. After tapping on the panel a few times, it finally worked. I eventually took the climate control panel out and discovered a short (burnt connections) at the plug. Cleaned & poked and greased the connections - and it worked fine. I ended up ordering a used one anyway..... Just for the sake of the unknown.

Since you swapped a CC panel - you may have a bad connection at the plug on YOUR end. Just a thought....