No heat in 2002 4-runner; help!

Well, we have a problem with no heat in my wife’s 2002 Toyota 4-runner. She gets heat, but not much. My nephew came over this weekend (he has a 2004 Toyota pick-up) and we tried to fix the problem. First we changed the thermostat; no improvement. Then we swapped out the relay for the heater from his truck to the 4-runner; no luck. We then swapped out the entire control cluster for the heater/air/fan/directional controls from the dashboards of both vehicles; no luck. I had an infrared temperature reader and we were getting 80 degrees out of my wife’s vents while we were getting readings of 136+ degrees from my nephew’s vents. Her vehicle does not over heat.

Any ideas/suggestions before I turn myself over to the mercy of the dealers?

Probably no connection between a Dodge and a Toyota, but a fellow I'm acquainted with had that same problem with his Dodge Dakota pickup last week; took the dealer two days to figure it out and they finally concluded that it had a warped thermostat housing that was causing a good thermostat to stick open. That was the first time I had heard of that happening.

Other possibilities are a partly clogged heater core, or an airlock in the system that is preventing flow of coolant from the engine through the core.

Are you getting good airflow, just not hot air?

The valve that controls the flow to the heater core moves when actuated; I suppose it could be broken on the inside... That was one thing that my nephew suggested to try: bypass the valve with a section of rigid tube top see if the fluid flow increased but we didn't have anything handy to bypass the valve.
Airflow is good...

DMF,
Go to this site http://www.2carpros.com/index.htm I think someone had the same problem with the heater valve. You can search by problem or make. Hope this helps.