Heater Problem May Be Fixed...

[TexasLexus94]

Finally had to use the heater on the '94 LS this year. The first time recently it worked fine-yesterday it would only blow cold, cold air. The dampers and the like seemed to be opening, but there was no heat. All the lights and fans etc work fine.

So I checked out the little servo type things next to the glove compartment, and couldn't tell what was wrong. The only other things I did was:

1. Topped the radiator with water-it seemed to need a quart or so.

2. Drove down the street, after I had given up, and punched the defrost button for grins. Lo and behold, hot air! Punched the other buttons-hot air! So I'm simply wondering what might be wrong, or not wrong. The only other thing I noticed was that the top radiator hose was quite warm when warmed up, and the bottom one was cool. After filling the radiator with more water, they seemed to reach approx equal temperatures. Could my lack of maintenance have caused a loss of heat? Or did punching the defrost button cause a miracle? Thanks for your ideas, and Merry Christmas to all.

[SKperformance]

if the heater core was full of air then you would get no heat until you filled it.

No exact reason for it to work but a probable one.

[RFeldes]

It seems the defrost button is causing a surge of posts. Maybe, if you called a service advisor at Lexus he could clue us all in. Please do and post your findings. Take notes.

[pfleyva]

My '94 has a similar problem, except it happens all of the time:

The heater blows cold forever.

If I turn off A/C, turn heat selector to "HOT", fan to low, select the air on feet/defroster button, then wait about five minutes the heat will get warm.

[wwest]

On the 92 LS400 there is a hot water heater flow control valve inside the engine compartment at the top center of the firewall. It is operated by a push/pull cable connected to the reheat/remix blend door servomotor inside the A/C plenum. In max heat the cable should move the water valve to full open and in max cool to full close.

If your LS has the same valve that would be an easy place to start checking for no heat.