Any Toyota Techs on here?

we had a dual system in our suburban and the rear core operated the right side of the cabin..? Right side was way off temperature wise. we also had a no heat issue and the coolant was very low. Oh yeah, 92 toyotas came with an electric servo that regulated the heater on climate controlled vehicles, its on the firewall passenger side. It regulated the vacuum to the heater control valve dashpot. I had no heat driving back from Barstow and it was about 40, we froze. Turns out I could have switched vacuum hoses and bypassed it in about 10 seconds with no tools...duh!