Now that everything is vice versa, you have to drive backwards to get heat at idle.

Seriously, though, now you may have an auxiliary pump problem. Set your heat at maximum and see if you've got 12 volts at the pump (car not running and key in position II). Or you can just listen for it. It's an obvious noise under the hood. If you hear the pump then something else is wrong. If you don't hear the pump and you've got 12 volts, your pump is seized. Been known to happen, and if so, at least disconnect the pump until you get it fixed. A bad aux pump can fry the climate control.