Thanks Bill, but I was referring to the installation of a shutoff valve in the engine compartment that actually prevented the circulation of hot coolant into the heater core during the summer months. This was a manual valve that had to be turned on or off by hand. Sound familiar?

 

Don, go here http://www.hybridcars.com/forums/hea...***-t1567.html

for information on the heater core bypass

 

That's it! Thanks Bill, I was looking on the wrong forum. That's why we need you around here.

 

If you wish you can accomplish virtually the same thing by putting the A/C system in the recirc mode and in lowest cooling setting. That will result no need to COOL incoming outside airflow, HOT incoming airflow, and the remix/reheat vane/doorwill be fully closed to any portion of the system airflow being reheated after being first cooled via passing through the evaporator.

You might also be pleasantly surprised at the not insignificant improvement in FE that results from either of these procedures (complete shutoff or..) due to the A/C compressor's "on" time be dramatically reduced.

The shortcoming of the above procedure is you might now need to manually (often..) adjust, re-adjust, the blower speed for attaining/maintaining the cabin's passenger temperature comfort level. The other relatively minor short-coming is that since HOT water will continue to flow through the heater core the surrounding structures will soon become heated due to radiant heating effects. Many new water cooled 911 owners have complained of the discomfort resulting from the entire front-center "hump" becoming heated this way.