Vents switching to defrost on hills or under power
My '96 with manual HVAC controls has started to act up. If it'* set on vent, and I go up a hill or step on it hard, the vents switch to defrost.
I know it'* becuase it'* losing the vacuum and it 'defaults' to that, so I went searching under the hood. I found the vacuum cannister under the right front fender, and sure enough, there was a little hole in the tube coming out of it, so I taped it up. That made the controls respond faster, but they still do the same thing.
So where else should I look for leaks? Or is there a check valve somewhere that quit working?
1996 Olds LS, 198,900 miles: RIP...