Had a service call today on a Carrier roof top M#48TMF012---501HQ. Found unit locked out on failed ignition (gas valve would not open with 24V). Replaced valve and checked operation. OK. The new valve (White Rodgers 36H54) was an excact replacement and came with a wiring diagram that showed rectifiers inside the valve. Does anybody know why there would be rectifiers on gas valve? Also when I removed the common wire from the valve when the Carrier control/ignition board was in the heating mode, the board would lock out on internal fault (8 flashes). This is the valve http://www.partsguy.com/pdf/36H64-463%20INS.pdf