Little to no cabin heat 2009 2.7l AC...At the end of my proverbial rope

I've searched multiple times on this and other Toyota forums.
The last post on this page best describes the problem I have.
The best piece of info I could get was a TSB #0072-09.
This TSB notice (not a recall), goes over how the temperature damper (flap) that controls air going through or bypassing the heater core has a foam cover that comes undone and can block the flow of air through the heater core, thereby limiting the amount, and temperature of the air through the ventilation system.



I have taken my dash off (not the first time), and managed to get the bottom of the HVAC system off this time. I took off the bottom of the system (circled in blue). It sits about 2 inches above the transmission tunnel.

I then swung the heater core (circled in red) out of the way so I could see the air temp. damper flap.

I could seethe air temperature damper door, and could see that it was covered in foam, but the foam had definitely NOT come loose from the flapper door, and was not blocking the heater core.

I actuated the servo motor that operates the air temp. damper using the dash temp dial, and it worked just fine.

I can see the flap or flaps that direct air to the appropriate vents, and it seems to work just fine; when it's on floor ventilation, it directs ventilation to my feet, etc.

I undid the servo motor and actuated the air temp damper flap by hand. It seemed to work fine, and either directed air through the heater core, or with the flap perpendicular to the ground , away from the heater core. It is only possible to see this flapper with the bottom taken off the HVAC system, and the heater core out of the way.

I put the heater core back in place and put the HVAC system back together.

I drove the truck until it the coolant was warm (15 km's) and although it would blow warmish air, I never got anywhere near "Hot" air coming out of the vents.

I left the truck running and actuated the flapper valve by hand with the fan on high. There was considerably less air coming through the vents when it was directing air through the heater core (is this to be expected? It was considerably less airflow).

Regardless, with the flap up (air is directed through the heater core) the air coming out of the vents was lukewarm at best.

It's freezing outside here (but I'm steaming frustrated!), and I'm so pissed off at what should be a pretty simple operation. I cannot see what the solution is.

Has anybody run into a similar problem? Could it be that I am not getting enough coolant to the heater core? It gets hot, but not very hot.

Am I even looking at the correct part or is the temperature damper door that fixes in the top half of the HVAC unit and associated with the mode selector?

Is there something inline to the heater core that I don't know about?

Or more likely an issue in the HVAC system (which by my amateur eye, looks just fine)?

Thanks in advance.

 

I'd replace the thermostat if you haven't already. Very cheap and not hard to do. Eliminate that possibility

 

Thanks, yeah, good idea, I will try that.
My tercel had a thermostat that got stuck open, but the car ran poorly (rich) and the temp gauge hardly registered, which isn't the case here. (Temp gauge shows normal operating temp/ truck runs fine).
I just included a link to the TSB notification in my original post, and my problem is exactly what it describes; decreased airflow and little/no heat.
What I can't figure out after studying the TSB notification, is if they are replacing the flap in the bottom of the HVAC unit (the one I can see that looks good), or the top (the one combined with the mode damper control assembly; I can't see this one). I was looking at the bottom flap, and it seems fine, but the problem as they describe it continues.
It looks as if the bottom flap and one of the top flaps that makes up the mode damper control assembly have the same part number...

 

According to this thread , the Air Mix control servo is solely in charge of hot and cold air mixtures. This is the flap that I can see that appears to work just fine.

 

if temp gauge is normal range, and blend door is operating properly, that leaves heater core partially plugged,/plugged I usually unhook the lines at fire wall or at the engine and used compressed air and water to "back flush it" typically I have dodges roll into my shop with little or no heat, and if the first two things I listed are good, I blow out the core, and every time I get smoking hot heat out the vents.
worse case you end up swapping out a heater core.
blowing out the core is quick and easy, and if you see any improvement, it confirms the heater core is bad.

 

I'll try that after work today and report back.

 

I would regulate the air pressure down and be gentle. One time I drained and then washed out a gas tank with water and after letting it drain I blew it out with ~80 PSI air and it ballooned out like half an inch This was just sticking the nozzle of a blow gun in the fill opening.

 

Replace the heater hoses. I doubt they are plugged up or restricted but you never know.

 

OP, did you ever take a close look at the small plastic pin on the lever of the heater flap control? It engages the cam of the heater flap control and known to be fragile. I'm talking about the one driven by the servo that is lowest down and closest to you as you would sit in the pass seat.

 

Run it until it is at operating temperature, then feel both heater hoses... if one is noticeably cooler than the other, you have a clogged heater core. I had this problem with a jeep a couple of years ago. I pulled both heater hoses off the core, then hooked a garden hose to the output side of the core and backflushed the core. It spit out an amazing amount of crud... but worked fine after that.

-Bear

 

OK, I have heat now... a lot.
I added garden hose fittings to the inlet and outlet of the heater core and flushed it about 20 times each way. I didn't see any crud come out. Then reattached heater core hoses.
I also replaced the thermostat, and then burped the system as best I could by splicing a garden hose flushing tee into the heater core inlet hose (the uppermost hose that sits near the firewall above level with the rad cap). I had a funnel attached to a garden hose going into the flushing tee, and kept filling the funnel while the rad cap was off.
All the coolant that escaped via the rad cap was captured in a pan, and then the process was started again.
I replaced the rad cap, and clamped the hoses on either side of the flushing tee to avoid any air entering the system before removing the funnel and garden hose, and putting the cap on the flushing tee.

I did try using a vacuum purge system, but it only drew back in 4 of the 8.7 liter cooling system capacity.
(My mechanic must trust me, as he sent me home with his Snap-On coolant purge system for the weekend.)

In the end, I actually think it was mostly due to the thermostat, or maybe an airlock in heater core. The inlet pipe to the heater core was scalding hot, but the outlet was warmish to the touch.

On the plus side, I can now drain and fill a Tacoma cooling system in the dark in about 15 minutes

The thermostat looked a wee bit rusty, yet the coolant was Toyota coolant, and still tested great, with no discolouration.

 

All servo motors were working fine.

 

Wise advice. Start with the simple stuff, even though it showed no signs of malfunction.

 

Cheers!