Bill,
On the Poly water (in) from the intake manifold goes to the driver's side port. Water (out) from the passenger side port to the water pump. You can check the temperature control cable making sure it's connected to the lever at the heater. Sometimes when the cable is pushed to (low) or closed the wire will slip out of the lever. Also check the vacuum line controlling the (cool) port making sure it's closed when the (heat) port is open.
At one point my unit was stuck between heat and defrost with no heat coming out. The lower heat door was stuck on the carpet.
Nick
From: "Bill M"
Subject: Re: Heater Woes
I'm pretty sure the FSM showed the water pump port going to the pass side but I'll revisit it...I've been wrong before!
I'm pretty certain the internal door is moving, but even if it wasn't...if I set the temp to hot, I should still get hot air....correct?