Question about 2003 Toyota Highlander

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Heater does not work and check engine light is on

I turn the heater on and only cold air comes out. The air conditioner works perfect.

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  • tsmith2305 Nov 30, 2008

    i have same problem heater and gage wont heat up i replaced thermastat and antifreeze heater control valve works heater core is not plug let it run with radiator cap off for hour and a half somebody said air was in the line nothing works any help thanks tom

  • bhtto Dec 02, 2008

    My wife just called this morning with the same problem on her way to work. She said that it was blowing fine, and she was getting warm, so she just turned the fan down. Then, she felt like cold air was coming in, so she turned the fan back on heat, just cold air.

  • Anonymous Dec 19, 2008

    I had the same problem (cold air only). I removed the knob for the heat control, and tightened the nut. This helped for a day or 2, but then it was back to cold air. A mechanic told me to try hitting the control knob. When I did, it actually made it colder. I took the knob off again, and if I push down on the bolt that sticks out, it gives hot air, but I can't find a way to keep it in this position permanently. The mechanic told me that the heat control unit may have to be replaced. It's $750 part (plus labor)!

  • Serge Rousseau Feb 28, 2009

    no heat at all


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Please see
It's usually broken solder joints on a cable behind, and feeding, the temperature knob.
I repaired my 2002 Highlander yesterday thanks to this site.

Posted on Jan 21, 2009

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I have the same problem

Posted on Feb 28, 2009

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Wow, I have the same problem, heater blows out cold air and AC works fine. All of the whack jobs at work told me repeatedly your thermostat is bad. I changed it even though i felt like that wasn't it, and low and behold the same problems exist (no heat). Whats the next step? someone at the auto part store said try the heater Valve.

Posted on Nov 23, 2008

  • bigbard Dec 03, 2008

    I fixed it, it was actually the knob itself (the hot/cold switch).


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It is most probably the problem with blend door or blend door actuator. But just in case I would suggest to follow the entire procedure:

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

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the motor wiring is bad.i had the same problem.its the wiring to the blower motor cost me $70 for the wires and $40 to get it put in hope this help you good luck

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