I don't know if the heater design on 2nd gen is similar or not to 3rd gen 4Runners.

But on the 3rd gen 4Runners there is a cable that controls the heater air bypass flap door.. If that cable slips out of its bracket, you won't get any heat even though the heater core is hot.. All the air is bypassing around the core..

Happened on my 3rd gen... On it the cable is exposed on the outside of the heater especially on the bottom where a passenger could inadvertently kick and pop it out of the bracket that holds it in position..

2000 4Runner,V6,Auto,31's, Sliders, Skids, On-Board Air, Air Shocks
Related Interests: Welding, Ham Radio, Road Tripping (Blue Highways), High End Video/Audio Systems