my 92 lexus sc400 is starts to become real hot inside.... why? heater is off, and it seems to still have some heat coming from under the center dash area while AC is on. Weird...
You may have a failed heater control valve, stuck open. It is on the firewall to the left of the intake manifold, you'll see the hoses going in and out of it. They factory pieces are pricey, about $325! You can get around that by using a Motorcraft YG-368 replacement and installing it with the hose slightly turned.
Search Lexus SC 400 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Lexus SC 400 Experts