Heater blend door stuck?

so the little lever that the servo motor opens and closes controls the heater valve (and air mixer, I guess) so I'm kind of leaning towards not putting a new servo in and just opens and closing by hand. I can literally do it at a stop light, it's that easy... I think the servo is bad, but when I supply power to it I get it moving each way no problem so I'm not sure what else to try. The control panel was a wash, I tried another one and got no change. tested per diagram and seems to test fine,

 

Well I am officially out of ideas. Power is not going to the servo motor and I can't figure out the disconnect. The relay and the control panel are both working properly AFAIK, the only thing I can think of is maybe the amplifier thing that is up in the dash behind the control panel?

 

What wires did you test for voltage on the air mix servo harness?

 

just the wire that goes to that servo specifically, everything else works like it should, it's just the servo that opens and closes the air mixer when you change the temp from hot to cold

 

Did you supply voltage to the AM servo? And check continuity like it's listed in the fsm?

 

I did not check continuity, but did apply the required voltage and tested that the servo actually operated... I also replaced the servo with a used servo. I also replaced the control panel with a used panel. I've also replaced the relay. So far no change and I've just been opening and closing the blend door by hand since it is very simple without the servo installed in position.

 

Strange. I guess it should be implied you checked the ECU-B fuse?

The FSM has a lot to be desired. But if you supplied vlt to pin5(-)&pin4(+) and the arm moves to the warm position, the AM servo is probably good.
The AM servo receives vlt from the A/C control assy (blue to red knob). Have you tested vlt there? Just to rule out the "new" used control assy isn't faulty?
But if you replaced all you have said you've replaced. And it's all the same result. I'd try making sure all your connector pins in the circuit are straight, making clear contact and not burned or scorched in any way..

 

I did not check ECU-B fuse... I will check that when I get home today. Is that one of those funky 50A/40A fuses? I looked at all the fuses from top down and they all looked good.

as far as the servo goes I wouldn't say it had positions.. When applying voltage the arm just spun clockwise or counter clockwise until pwr was no longer supplied. In the manual it seemed to state it should move up and down about 40 degrees, but when I applied voltage it spun a full revolution in either direction.

 

7.5A mini

When you replaced the A/C/Heater Control Assy did you replace the amplifier too? The whole deal?

 

No the amplifier looks pretty difficult to get to and I was really hoping that wouldn't be the issue! Not sure how to test that guy, but if he is the problem he can stay broken. =)

 

There's a whole testing procedure in the last pages of the AC section of the fsm.

Isn't the amplifier in the housing that the heater control is located??

Edit: doesn't look too difficult to get to...

 

If it is I'll take apart the control panel again... I thought it was up in the dash behind the control panel! The new panel came as one piece and I just hot swapped them and didn't get a working servo and cussed at the time wasting trying to get the damn knobs back on as that was the hardest freaking part

 

Did you reverse polarity on pins 4&5 to get to move CW CCW?

Then you might of unintentionally swapped the amplifier.

 

Yes I reverse polarity & I swapped the entire panel that I received so I don't think anything got crossed, but if there is a test method for that I may try tinkering with that if this 7.5A fuse isn't the culprit... which I hope is the case, because the panel/servo/relay are all original on this truck and look to be in pristine condition.

 

If your ECU-B fuse was blown, you'd have other noticable issues.

I'm just having a hard time with you replacing all the parts you did and still having no heat. The circuit isn't that complicated.

In thinking there's a bad connection on a connector somewhere.

 

There is a connector that has nothing plugged into it right down there near where that servo is, but it is likely for some option this truck doesn't have... perhaps for a doublecab version. I can't see anything else that would be an issue... Supposedly the only thing the ECU-B fuse controls is : SRS warning light, air conditioning system and I have no other symptoms. I will say when I pull the parking brake I don't get a parking brake light, but that is probably unrelated.

 

That unused connector is probably for the glass break sensor...

No I mean, I'm leaning towards a male pin being bent inside of a connector, and not making decent contact, or a burnt pin maybe..

I would just look at the air mix servo harness and see if you can tweak the pins on it so they make better contact.

 

I tried probing the pins on the connector to see if I was getting any voltage out of them and I couldn't manage to get anything. Checked ECU-B fuse and it seemed fine. Going to look up the page on testing the heater control and try parting it off the donor panel and see if I can get anything... After that I am official out of ideas

can you post the page for testing the amplifier?

edit: here is the donor hvac controls in all their glory. I see nothing that indicates an issue and I find it hard to believe that the original or this one has any issues... at least in this state I can test and confirm this much easier...

https://imgur.com/a/hWkm5

 

The last section, at the bottom of the page. Under Heater Control Assy:

http://www.markofshame.com/fsm/03_Tacoma/

 

testing the control and it seems to stay at a constant 2v across cold and hot... and one of the chips on the board burned the shit out of my finger. Not sure if that means it is bad or if I am just not testing it right.

(a) Check that the resistance between terminals 11 and 13 is approx. 3.0 KΩ

I'm getting 2.55 resistance and I almost cried in front of my 9 year old because of the burned finger.