Fitted new external timeswitch to potterton promax 33he and now heating won't fire up. I have wired in a horstmann c17 series2. The existing integral time clock works when I put it back in, I have checked the new times witch is sending current to the pcn but it still doesn't fire, please help.

Darren

Darren, January 2014

You may have to bridge the switch pair from the existing clock,there may be a connector on the PCB that allows you to do this

toptrish, January 2014