Re-reading your question I now realise your problems is with the above gas heater and not the Fanmaster.
This heater is indeed controlled from the 12 volt switch on the wall and only a gas supply is required other than this. When switched on the gas valve opens and you should here a spark as well, this should light the gas and a signal is then sent back to the switch to tell it the gas is alight. The control switch then 'suspends' the start cycle by leaving the gas valve open and stopping the spark, the fire should then switch off as the temperature set on the dial is reached and on again as the temp falls. If at any point the flame goes out, the control instantly re-instates the start cycle and attempts to re-light for about seven seconds.
When the green light flashes, it means the start cycle has completed and a flame has not lit or it does not recognise one is lit?...in which case it shuts down and the light flashes to show a fault.
First thing to check is that you have a gas supply, after this that the gas valve opens, (that I think is the clunk you heard), and that there is a spark. If all three it should light and either it is the wrong type of flame? or the control switch is faulty. Behind the front cover, (two screws hold the front on at floor level), is a 'sight' hole where the flame can be observed and this should be bright blue and dancing on the four burners to make the flame sensor work, any wispy yellow flame and you have a blockage which will need clearing...not a job for the in-experienced. If it does light but goes out then the fault is the control switch or a connection between. Most switches have six wires coming from the fire and the yellow one is the flame sensor, a poor connection here often stops it recognising the flame. The plastic bar connector for the wires pulls off of six pins on the board and doing this several times will scratch a new connection and can often solve this problem.
Damp is also a killer were electronics are concerned so take the switch indoors to dry out over night and see if that cures the problem. You did not mention you heard a spark and if the spark generator is 'dead' you will need a new one, but first you can put 12 volts straight to it to make sure. It should be marked but the green wire is + and blue -. If it works like this then again the control switch is faulty.
The same as for Fanmasters and other Carver product, Arc Systems can supply assistance and most spares.
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