I am trying to hook up a 3 wire (red,green, and white) thermostat. The old thermostat was an automag mercury type that says r+b heat only. All three wires where hooked up. I installed and now my heat will not shut off upstairs. I have 4 zones. I used same thermostat downstairs. Seems to be working fine. I have red to rb jumped to rc, green to w and white to y.

You have a old Automag zone control system. See the Automag company below.

You can add there relay or similar to make your 3 wire zone valve work.

CNV84 Relay
Relay to adapt existing 3-wire thermostat system to 2-wire thermostats. (One relay required for each thermostat.)

OR you can just replace the valve head (I recommend this instead of a relay)

Call them. They have been around a long time and are very knowledgeable. Many years ago I installed a bunch of there stuff on contract jobs for the US Government.

Automag division of KCI Industries, Inc.
Manufacturer of "Fail-Safe" normally open Zone Valves

1111 Hill Street, Jessup, PA 18434
(800) 451-2002
(570) 383-2428
FAX: (570) 383-9820

Web site loaded with info.

AUTOMAG