The heater on my 2005 Toyota Highlander suddenly puts out cold air for a period of time, then goes back to sending warm air. Sometimes it lasts quite a while. If I change the heat control it seems to return to normal. The temperature guage doesn’t change during this problem. In Minnesota, I need heat!
I believe I have the answer to your Highlander heater problem. I had the same problem, and I fixed it myself for free. I first noticed an intermittent problem with the temperature control of my 2003 Highlander. The problem of erratic heat output eventually got worse to the point that I got no heat at all. I searched the internet for help, and I came across a great site that described the problem and the solution. Go to http://www.tundrasolutions.com/forums/highlander/32217-heater-quit-sort-of-14/ . When you get to this web page, look for the posting by “Senator22” from 12/07/08 at 4:04pm. This posting has photographs describing the entire repair. This repair consists of soldering wires that have broken over time in your dashboard due to your rotary temperature control knob being loose. A repair shop will charge you approx. $1,000 to fix the problem because they will replace the entire control unit rather than performing this repair. You, or a friend, need to have a bit of soldering skill to perform this repair, but it is certainly within the capabilities of most do-it-yourselfers. The good news is, you can remove the unit from the car and perform the repair in the comfort of your home or workshop.