Opened up my ratty heater box the other day and took a look inside. It wasn't easy. Destroyed the little silver collars that cap off the evaporator drain tubes which penetrate the firewall into the engine compartment.

Also destroyed the "h" shaped heater valve pictured below in order to remove the heater core.



At any rate, does anyone know how this heater valve works? On a 68-70 B-Body equipped with AC the heater core is rather long as though it were two heater cores joined together. Which tubes are the inlet and outlet? and what's the third tube for?

Post deleted by SuperCommando

The water by pass valve in the top pic connects to B and C outlets in the heater core via small connecting hoses. If you took the top pic and flip it the B connects to the straight tube on the valve and C to the 90 degree bend. The valve is operated by linkage which connects to the air conditioning door. It is operated by the AC door actuator . So basically coming out you have A and the outlet on the by pass valve

Thanks, but between the 3 connections available on the core, which ones are considered the heater core "inlet" and "outlet"? How does the water flow in and out of the core? Does it come in through A on the core and out through either B or C?

Just read a post from the folks at DMT and I believe they may be looking to repro the drain tube collars you said you ruined.