Heater control takes until warm up before turns on

RBENNETT58

MEMBER
1999 LEXUS SC 300
3.0L
6 CYL
2WD
AUTOMATIC
210,000 MILES

First start in the morning the heater control panel just has back light. Takes approximately 20 minutes and the controls come on and everything is fine. Drive the car to work and let it sit for 8 hours and the heater control panel is fine. Just takes a while in the morning. Any ideas?

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

If you have automatic climate control, the system will not work in heat mode until the cylinder head temperature is at least 100 degrees. This is the way the system is designed.

The defroster should work right away but will not blow heat until the engine warms up.

Roy

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Thursday, October 10th, 2019 AT 2:24 AM

RBENNETT58

MEMBER
2 POSTS

Agree but the climate control is blank until the car warms up. It took about 1/2 hour this morning before the LED lit up and the functions started working.

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Thursday, October 10th, 2019 AT 11:50 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Okay, you never said the screen was blank. I attached a wiring diagram for you to view. When it does not work, you need to check for voltage to the control head.

Check for power on the highlighted wires in the diagram when the system is not working.

Roy

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