2004 highlander. In the summer, occasionally the air conditioner pumped out hot air. Now that it is cooler and I need the heater, the dash temp conrol allows only hot air, no matter what the setting. If I change the route of the air -feet, face, etc. it may correct temporarily. Jack [email protected]

SOURCE: Fix Highlander heat problem but created new one

Check your vaccum lines

SOURCE: air cond goes from cold to hot on coldest setting or if its on hot it will start blowing cold

You have a broken wire on the heater control potentiometer. You can either order and replace the control, which is expensive, or you can remove the control, and disassemble it, and re-solder the broken wire. We do this all of the time; resolder the pots bacjk on to the main PC board.

SOURCE: 2005 highlander heater problem

I'm glad I could help. I'm reposting the solution below in case anyone needs it in the future. Please be sure to rate it for me!

Pull the temperature knob off and verify the thin 12mm nut is installed and tight behind it. I have seen several of these loosen up allowing the knob to turn but intermittently have no effect on temperature.

SOURCE: 2002 HIGHLANDER MANUFACTURER CODE

no you need an a/f sensor if the code is for a bank one it is located on the exhaust manifold on the back of the engine compartment vise versa if it is for bank 2

SOURCE: Toyota 04 Highlander Temp Control Problem

Hello. Thank you for requesting me. We have been seeing a large amount of Highlanders with temperature control issues. A replacement control is in the proximity of 900 dollars. After the fifth one sold, and some really unhappy customers, I decided to see what the issue was that was causing the failures. It turns out that the problem is nothing more than a broken wire of two. If you are handy with tools, and can use a soldering gun, you can fix it yourself. The problem with the controls needing replacement is a broken wire or two at the circuit board that controls the temperature (the center knob). This is unfortunately common, albeit an expensive repair. Here is how you can fix it yourself: What you will need: Pencil-type soldering iron, rosin core solder, a Phillips screwdriver, a 10 millimeter socket, extension and ratchet. First, remove the plastic fascia that surrounds the radio/heater-AC control. (Be careful to not crack it when removing it.) Next, remove all of the 10 millimeter bolts that holds the Radio/AC-heater control assembly to the dash panel, and unplug all of the wiring connectors. Next, remove the three control knobs on the Heater/AC control panel, and the silver nuts that holds the controls to the panel. They pull straight off. (Under the center knob, you will probably find a loose nut, this is what caused the wires to break, the control is loose in its holder.). Next, turn the assembly over, with the back facing upwards. You will see a rectangular black box. Remove the screws that hold the black box onto the back side of the front of the control panel. There will be a ribbon-wire connector that will need to be removed from the front panel; be careful when removing the black box?s connection, and take care to not damage the connection ribbon wires. Next, remove the entire circuit board from the panel cover, by removing several Phillips screws, this will allow easier access to the control board that needs the wire(s) soldered. At this point, you have two choices: You can solder the broken wire back onto the control?s board, or, if you desire, you can remove the ribbon wire, and replace it with different wires; personally, I choose this path, and I use telephone wire, three lengths, that I strip and solder to both locations, each of the three on the main board and the other end on the control board. Either way will work, as long as you solder the wires back properly, and avoid any possible shorts by allowing the solder to touch an adjacent lead. Once you have soldered the broken wires from the temperature control board back on to the main circuit board; reassemble the parts and refit it assembly to the dash. Thanks for choosing FixYa for assistance today; I hope that this helps you out, and saves you a bunch of money.

Testimonial: "Thanks so much for the detailed instructions! Sure enough, 2 wires were broken. My husband was able to make the repairs, and the control gauge is now working perfectly. Thanks so much!"