Have Toyota Questions? Ask a Mechanic for Answers ASAP
Thank you for allowing me to help you with this concern today and am sorry to hear that this is happening. I will have to ask you a few questions so that I can get a better understanding as to what may be going on with your Highlander.
When you say that the heater isnt working and you slap the dash and its starts working, are we talking about the blower motor? Like no air comes out and then you slap the dash and now it blows hot air?
So the blower works at the time and doesn't quit?
Where exactly are you slapping the dash to get the heater to work?
When you do this slap, does it start blowing hot air immediately?
I see. Have you felt the center temp dial? Does it feels wiggly/loose?
There is a very common problem with these that I, along with thousands of Highlander Owners wish Toyota would recall, is that the wiring that goes from that switch to the circuit board breaks (soldering) and needs to be fixed. You can replace the unit at the cost of about $800 or if you know of someone who can solder well, then pull it out and solder the wires back.
Here is a silly video that talks about this concern and you will notice that most people complain about the cold air goes to hot (it happens both ways actually). The loose nut "fix" is just temporary in the beginning and the unit will again fail over time because it is the wires that become loose.
Here is a video showing the Part 3 phase of repairing the wires that go bad.
And last but not least, a tutorial of taking it apart and also fixing the wires...
Does this make sense?