airlock in 1/2 of a zone?

heating split into 2 zones
presumably you have 2 room thermostats?
2x 2 port zone valves?
& a double channel timer for heating?

if 1st heating zone works ok then just turn on heating for 2nd zone [1st zone OFF]
does boiler fire up?

if YES
2nd zone radiators should heat up in theory
unless system is
airlocked [fill, bleed & vent]
severely blocked [needs flushing]

if NO
i would check correct operation of 2nd zone
room thermostat
timer
2 port zone valve

they are just simple switches
if power goes IN & switch is ON power should go OUT

the component that fails this simple test is the faulty item & should be either repaired or replaced

this does involve a certain level of electrical competence [above the level of wiring a 3 pin plug]

you are best placed to decide if you have the necessary skills/experience/competence

if in any doubt get a professional

Q
January 2014