A very Intermittent Ravenheat RSF 100ET

[Bravo Tango]

I have a RAVENHEAT RST 100ET that is very intermittent. Whether on Heat or Hot water, the Fan and motor run fine but doesn't always fire. After a couple of more tries it still may or may not fire. If it doesn't the red light comes on. After resetting, again same situation. Sometimes it will work fine for a couple of days, at other times after resetting some 20 times, it will suddenly work ok. I don't hear it firing either. Relay 3 just will not operate. Very occasionally it will fire and light for a split second, then fail again. I've replaced both thermistors and I've checked the air-pressure switch by blowing into the pipe that goes into the flue and it works fine. Got a second hand tested control board this morning, but same issues persist so I assume board is fine. I can't find a circuit diagram on line that shows exactly the same board. Is there any way of checking the gas switch and the electrode cables? Any other suggestions are most welcome!

 

[muggles]

Sorry but you've already gone beyond what a DIYer should be doing and forum rules prohibit advice on this kind of stuff. Time to call in a professional

 

[OLLIE20]

I have a RAVENHEAT RST 100ET that is very intermittent. Whether on Heat or Hot water, the Fan and motor run fine but doesn't always fire. After a couple of more tries it still may or may not fire. If it doesn't the red light comes on. After resetting, again same situation. Sometimes it will work fine for a couple of days, at other times after resetting some 20 times, it will suddenly work ok. I don't hear it firing either. Relay 3 just will not operate. Very occasionally it will fire and light for a split second, then fail again. I've replaced both thermistors and I've checked the air-pressure switch by blowing into the pipe that goes into the flue and it works fine. Got a second hand tested control board this morning, but same issues persist so I assume board is fine. I can't find a circuit diagram on line that shows exactly the same board. Is there any way of checking the gas switch and the electrode cables? Any other suggestions are most welcome!

Your boiler is a piece of **** 15 plus year old scrap box landlord special, they’re throw away boilers. Get someone is who know what they’re doing to repair or better still replace with something decent.