Wiring diagram/explanation for 2003 Tacoma ac temp control

I have a problem with the temperature control for my 2003 Tacoma. Generally, I can fiddle with the (manual) temperature control and sometimes get the temperature to adjust. Most of the time, it is stuck on hot. I have observed the mix servo and it’s action (inaction) is consistent with the continuous heat. The servo will move a little but generally settles to the hot side. I purchased a used servo that I sure hope is good and it acts in a similar way, not responding to the temperature control knob. With the servo dismounted and hanging, I am able to manually adjust the air mix to the cold I need for summer driving. I know enough electronics to think that I can troubleshoot the system if I can just get either an explanation and/or complete wiring diagram that shows the details for the temperature control. I have a diagram of the servo wiring. My interest is in understanding the how the servo knows that it has arrived at the requested mix setting. Any help will be greatly appreciated.

 

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Thanks you. I am new to this forum. I looked at the links that you sent but didn’t see any information on the Tacoma AC. What am I missing?

 

Welcome to TW!

 

Wiring diagram for 2003 air conditioning:

The system outline on page 3 might help you.

 

Thank-you for your reply. I will share what I’ve learned so far as I have looked at the actuator: In the interim, I went ahead and opened one of my actuators. It contains a motor, some gearing and an odd to-me resistor. There are metallic metallic fingers that act as brushes as the resistor rotates with movement of the solenoid. I believe this to be the position feedback to the mystery dash temperature control circuit. The resistor had a fair amount accumulated grease that I cleaned up. I burnished the brush contacts and adjusted the angle of the fingers slightly to provide a little more pressure onto the resistor surface. Once closed up, I reconnected the actuator and gave it a try. The thing ALMOST works and certainly works better than before I worked on it. The “ALMOST” refers to a little erratic response as the temperature control is adjusted. I seem to be on the right track; I will make another stab at cleaning and adjusting and hopefully will have a working temperature control. I will appreciate having the wiring diagram to fill in my understanding on how this thing works. My first attempt at downloading the pdf was a fail. I got the spinning wheel of death but nothing was received. I will try again.

 

I was successful with the download. Thank-you again.

 

I, too am having trouble with my air mix. It wants to keep going to the hot side regardless of where the dash knob is located. Bought a new servo motor for the door flap but I left it uninstalled to watch where the white plastic arm/positioner would settle. It moves most of the time when adjusting the knob but still tends to turn towards the hot air side. I'm having a friend that works on RV wiring look at it.

 

Hello DanK83: my repair effort has stalled for now due to other events here. One of my problems has been to simulate the interaction between the dash control and the servo so that I can watch the feedback circuit. My hunch is still that the variable resistor that provides the feedback to the dash mounted circuitry is intermittent and when the circuit goes “open”, the controller sends the servo to an extreme position, in our cases, to the “hot” side. (Since my original servo and the used replacement servo both fail but settle in different positions when they fail, I think that points to the servos being at fault. The logic is that if the dash controls and electronics were the fault, both servos would act identically.) Making the connections to the connector on the servo so that I can manually provide power and monitor the resistor’s behavior is quite challenging. What I wouldn’t give to have one of those connectors that attach to the servo. I have not found a satisfactory work-around to make the connections. I continue to mull how I might make my test strategy work. If you are successful with your repair, please send along a note about what you found. I will do the same. Regards,

 

I've noticed at times that if I turn it completely to max cool it will sometimes go there and then turn back towards hot. If I turn the knob clockwise just a little so it's not on max cool it will turn back towards cool, not all the way though because the knob isn't set to nax cool. It takes a bit of messing around to get it just right. Another member of this group/site said the part that the turns inside, behind the knob gets dirty or worn out. I live in Maine and winter is fast approaching so I suppose it wanting to got to max hot is preferable over max cool until I get it fixed.