I've got a 93' sc400, and recently discovered that the heater and air conditioning aren't working. When I go to turn it on either hot or cold it just blows cold air, I've looked up to see if there's this issue with anyone else but haven't had much luck and instead of taking it apart or even taking it to the dealer I figured I'd ask on here first. Can anyone help me?

 

Start with the obvious stuff first. The heat valve works off of a vacuum solenoid valve (vsv). The heat valve and vsv are on the rear firewall toward passenger side with heater hoses hooked up to the valve. Make sure you have vacuum at the vsv. If you do then check to make sure it is getting power to the vsv or see if it is actually cycling the valve. It gets a little more complicated after that, check that and get back to us.

 

Weird stuff but this happened to me too. Checked fuses, control valve, thermostat good. It fixed itself today as I was installing my double din. I connected the climate control, hazard,etc plugs back in and started the car. Heater now blows freaking hot air like its supposed to. I have no idea how that couldve fixed it.

 

I have a feeling it might be the control valve, but I'll look more into it. Thank you!