Lexus SC400 Problems

Heating and AC Control May Fail Intermintently on Lexus SC400

Problem Description and Possible Solution

There are reports of intermittent failures with the heating and air conditioning control. The digital display might fail or the control might fail to switch between heater functions.

(34 people reported this problem)

Lexus SC400 Vehicles With This Problem

RepairPal Verified
Average mileage: 160,425 (107,000–203,000)
9 model years affected: 1992, 1993, 1994, 1995, more1996, 1997, 1998, 1999, 2000
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Brake problem? Or maybe a faulty head gasket cylinder?
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Viewing 1-15 of 15 comments
My ac/heat won't turn on. I thought a fuse might be blown b/c the whole display is out....not sure how to fix it.
My A/C and heater panel went out. Controls for defrosters and Temperatures are all not working. Tried checking_replaced fuse - still not working.
Sudden inability to use heat or air conditioning. Display panel does not toggle to exterior temperature. Thought it was a fuse, but this does not appear to be the problem. I have no answers.
the heat does not work it might come on 2 times the hold winter .what needs 2 be done bout this,do i need a new unit
Blow nothing but cold air. temp.guage in car shows heating up, replaced themostat, filled up radiator. let run ,air still ice cold
i had the same problem, i got a can of that electrical parts cleaner, for wires and stuff. i cleaned every fuse and the fuse box under the hood. i could not figure out which one may be for the ac so i cleaned them all. i let the car sit a little while so the cleaner fumes could go away then started it up and turned on the ac. works fine now.
no heat while idle or cruising. Could be disconnected or bad electric servo that controls vacuum to heater control valve (reroute manifold vacuum line past servo directly into top of control valve, "in the donut hole") or it could be low coolant that is not circulating in heater core. There is also a diverter valve in the plenum that swings from cool to heat, that may have a bad motor. First check is easiest: Check coolant level in morning, cold. Then reroute vacuum line, takes about 20 seconds once you find it. If it heats with constant vacuum then the little plastic switch valve is bad, $$$ for some reason.
a/c works but the heater may come on only at around 60mph. Otherwise it doesn't work. The temp gauge has risen slightly from dead center.