My goal here was to find the simplest way to decrease the heat in the interior of the vehicle without running the airconditioner.The coolant flows throught the heater core at all times, and with the fresh air circulation system warm air is blowing on your feet even with all the controls in the off position.

What I used:

a NAPA Heater valve part # BK 6601200 , two hose clamps , one 1/8" vacuum line tee, 6" of 1/8" i.d. rubber vacuum hose and 30" of hard plastic 1/8" o.d. vacuum line

I installed the valve in the 5/8" heater hose near the support over the valve cover.

Ok, here's what I did to operate it with the stock controls:

Behind the glove box there is a bundle of vacuum lines. I cut the red one and inserted an inline tee fitting using small pieces of rubber vac. hose to attach it.

Then used hard plastic vac. line inserted through the antenna grommet into the engine compartment , up to the new control valve, again attached with a small piece of rubber vac. line.

This turns off the heat in all positions except the two defroster selections (last two at full clockwise), regardless of the temp control setting.

It would have been nice to control it using the temp selector, but it is electrically operated. This was the simplest way I could find.

My plan is to just open the glovebox , disconnect the tee and cap it in the wintertime. For Spring , Summer and Fall weather this should work well.

Total cost: under $25

There really is a big difference in the circulation air temp., even with the fan off now!