Is it me or the heater?

Are you sure about that? The repair manual has information on the PTC heater, which is what GrumpyCabbie is thinking of, I believe. It does have the usual "if equipped" notes, so it's probably a regional thing, but it presumably must be included in some regions...

At least on the Gen II, it was only 165 W though, or about a tenth as much as a hairdryer. Those heaters are really only meant to give you a little bit of window defrosting ability right when you turn on the car - you probably won't even notice the temperature difference.

 

I believe all models have the Positive Temperature Coefficient heater, but the following specific conditions (2nd paragraph) must apply:

 

Positive Temperature Coefficient heater? So that's an electric heater?

Honest to god, I think there's some sort of conspiracy at work here, to make descriptions completely unintelligible. I'm starting to froth...

 

Agreed that engineer-speak should be translated into normal-speak (call it an "electric heater"), but Toyota has enough trouble with the Japanese to English translations.

 

Great explanation but not for everyone's understanding.

 

Yes, that's correct - though it's worth noting that the MAX HOT noted here is not the temperature setting that you see on the display, but rather the air mix damper inside the A/C system; basically, it's trying to get as much heat as possible from the heater core, and no air is bypassing the heater to moderate the temperature.

A PTC heater refers to a specific type of electric heater. The coefficient that is positive relative to its temperature is the resistance - so the hotter it gets, the higher the resistance becomes. Because the voltage applied is constant (probably 12V), this decreases the current (Ohm's Law; V=I*R). The equation for power is P = V*I = V^2 / R. So as the resistance increases (and current decreases), the power dissipated in the heater will decrease.

The net effect of this is that this heating element doesn't require anything else for a thermostat - it limits itself from getting too hot. Other electric heaters need some sort of thermostat, and a safety in case the thermostat doesn't work right.

(That's actually what broke my wife's coffee maker. It was getting too hot*, and so one of the thermal cutoffs blew. Being the good electrical engineer that I am, I took it apart, removed the thermal cutoff, and shorted it instead. Then the other one blew, and I figured it was a good time to get a new coffee maker.)

(*Or maybe the thermal cutoffs got too old. Either way, a PTC heater avoids this sort of failure by just not requiring any sort of separate temperature control.)

 

Thanks for that MacMan.

 

Idk my 2010 will roast your nice person like a Christmas goose. Even set to 73 it feels like you are being baked alive. I do not dare using it on max heat in fear I would be cooked. Like the others stated it would be most likely a thermostat issue which I think you found out. Probably just a defective one from the factory

 

Agreed. In the winter 74F is about the highest I can set it without being uncomfortable. Best wishes for a speedy fix at the dealer.