[motornut]

Originally Posted by nonstop

Another thing you can do..... Vacuum operated shut off - some cars use them for A/C. Not sure how to tap it into existing vacuum switch, but you could also wire up a toggle to an vacuum solenoid - sounds complicated but it's not. Just need to scrounge junkyard. Around here, there are some summer mornings that are cold and winter days that are warm. No real solid seasons, so an under hood valve might be a pain!

My Burbs (88) had a rear combined ceiling AC/heat unit,had a valve under hood, I think to block rear flow.The 87 was separate,don't remember the valve