Something unusual is going on with my climate control. I have no idea what is wrong but here are the symptoms:
1) AC works but I have no heat except occasionally a TINY bit from the floor.
2) Hot/cold **** does not affect temperature for heat, just works for AC.
3) Side dash vents blow hard but center vents blow very little air.
4) Window defogger vent on top of dash blows very little air.
5) No vent blows lots of air except the side dash vents regardless of what mode it is on.
6) Hoses leading to heater control valve are hot but I still have no heat.
The two main issues are no heat, and whatever is used to route the air on the climate control seems to be malfunctioning. I believe someone was behind the dash and screwed some things up back there as one dash panel was put back on improperly.
What should I start looking at as a cause and solution?
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If there's a clear sign that the air ducting has been previously messed with or worked on, I would disassemble everything and reassemble to see if there's something wrong with them or misaligned. As for the heat, check if the small hoses to the heater control valve are connected to where they are supposed to be connected. You'd figure it out when you see it. I unplugged those tiny hoses in the past by mistake while washing the engine bay and I also lost the heat no matter what I do with the climate control.
In addition to what KingPhilip said, the heater control valve defaults to open (actuator rod retracted) when there's no vacuum, which would happen when: a) in full cooling, b) engine not running, c) vacuum hoses disconnected.
Have you checked for any HVAC diagnostic codes? It's covered in the service manual if you're not familiar with the steps.
'94 SC400: Goodkat ... "It's not something people hear about. Falls on deaf ears mostly. This particular one has been over twenty years in the making."
I took it to the shop, it's still there.So far, he said the climate control harness connectors were brittle and damaged so I got another and took it to him. I will report back as I know what he believes to be wrong. He said he cleaned lots of stuff out as well. I don't recall exactly what he said he cleaned though.