Question about 1991 Lexus LS 400

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Lexus 1991 LS400, has a new Thermostat but doesnt heat up

I want to know why my car doesnt heat it has a new thermostat

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The thermostat is not the only issue to look at, you have a valve that opens and close water circulation through your heat core that could not be working, If your car is low on coolant the heater will not function, last but not least there is an electrically operated damper door than controld air flow over the heating and cooling coils to maintain a constant cabin temp. Also you have an interior temp sensor that tells the computer what the temp is so it can tell the damper door where it needs to be. The first thing is wait untill your car is cool and top off the antifreeze and burp the cooling system there should be a place somewhere near the thermostat for this purpose. Next check operation of valve in heater hose between heater core and engine, then check the damper dor for operation you may cn actually hear it if not you will have to locate it under your dash. I hope this makes sense to you, If you had a scanner you could probably tell what was happening and what wasn't working. If you need further info, for 20.00 at, you can get access to the professional service manuals for your car and every system on it. Merry Christmas! oh one other long shot would be a bad temp switch, just not as likely as the others.

Posted on Dec 26, 2008


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