No Options Apply Suburban hotwater unit wont run unless door is open.

[Sparksy]

Been away for past 3 weeks, some of which was offgrid. When running the hot water on gas i have a issue where the Suburban hot water unit will only run with the door slightly ajar. If closed the sound of the flame drops from normal "roar" to a softer sound and eventually the flame fails. Door vents are clear, flame tube is clear , flame rods are bright and as far as gas pressure goes, all 3 burners look fine when running at once.
Managed to use it on gas by tying the door open about 15mm with a bit of wire between catch and door.
Has anyone encountered this before?

 

[Drover]

Yes.................. someone had a thread going not that long ago, wish I could remember the cause, Im sure we discovered why.................

 

[jazzeddie1234]

Twas me! The flame is supposed to create a small current flow across the probes that is detected by the circuit board and that holds the gas solenoid open....until the board develops a fault and is not sensitive enough. The board is expensive so I just open the door each time I use gas.

PS don't try bending the probes as they will snap....don't ask me how I know this

 

[Sparksy]

Ive cleaned the probes but if it was the board then the board would instantly switch off the gas. In this case the flame slowly looses intensity ( for want of a better word) and slowly reduces over about 2 minutes. If I didnt know that the vents were all clear, I would swear that it was because of a sealed enclosure and the flame using up all the air in there but of course it isnt. Ill try swapping over the board and probe as I have new spares at home.

 

[Drover]

Many moons ago I had a drama with a HWS , would start up but would stay on for a few minutes or just shut down once the start time had elapsed, turned out the thermocouple had a bad connector and the poor signal would shut down the gas solenoid .. did lots of testing with the meter before I found it .....

If it works with door open then I doubt its the board does sound like the door closed may be distorting the frame and movinig the thermocouple just a mm away from the flame so it not getting the right temp and shuts the gas off, just can't see how it could starve the air flow though and the gas should shut off instantly ....

 

[jazzeddie1234]

It could be the probes but the board has a well documented fault where the sensitivity to the flame (well the current measured as the flame passes the probes) is well documented on older boards anyway. I tried cleaning the probes, bending them in and out of the flame, changing the air gate (looks like a hose clamp), adding an extra vent grill to the door....

Definitely interested in what you find!

 

[Drover]

Ive cleaned the probes but if it was the board then the board would instantly switch off the gas. In this case the flame slowly looses intensity ( for want of a better word) and slowly reduces over about 2 minutes.

I think thats the clue, the flame is either on at full noise or totally out, it doesn't vary as it doesn't have a pilot, its sparks and start ................ To me slowly dying would point to a faulty solenoid thats closing slowly instead of instant shut off or starving of air as you said but its not like the door seals off anything and how would closing the door effect the circuit board, its a most intruiging problem ..................... possibly a combination of faults ................. I too await the outcome .......