I have a hydrotherm hc85 serial #6135 I'm not sure how old it is it was in the house when I bought it. It is not working. It has 3 zone boxes. Zone 1 and 3 pipes are hot zone 2 box is hot and pipe is cold. Does the unit shut down if one of the zone boxes is not working. Also the switches on the zone boxes are they supposed to be on the left or the right. Zone boxes 1 and 2 are left and zone box 3 is right does this have something to do with it not working. I need to know how to fix the problem. We need heat.

By "zone box" do you mean zone valve? If so what brand?