Suburban Hot Water heater

It has been fixed. There are two solenoids on the heater. One was faulty so there was no propane flowing to the igniter. We had to replace the module with the two solenoids for a cost of $139 for the part and $90 for the labour. Thanks to everyone for their input.

Not exactly sure what your trouble is but mine started to malfunction a while back.

It would light but it would go out almost instantly.

I checked everything and found that the wire for the igniter was pulled out a little so I pushed it in hard and everything worked fine. I pulled the wire out and it malfunctioned again. The wire has broken inside the ceramic end. I stripped off a little insulation and pressed it in hard again and it has worked fine ever since but I know I need to replace the igniter. I guess it senses the flame somehow when it is lit and if no flame present shuts off the system.

I have looked at all the parts stores and can not find the igniter Sure would be good to replace it one day.

Try working the wire connector on the igniter board off and on a few times. And if you have some contact cleaner, use it on the connection. Flame sense is done by change between electrodes by presence of flame plasma or not.

The 'fault' light is on because it failed to light off main flame and prove main flame lit.

Reset by turning ON/OFF switch off wait 5 seconds then back on. Water heater will attempt to light off.
Watch it from outside to see how far it gets in sequence.
Does it 'spark'? Strong spark?
Does main flame light? Does it go right out?

Do you have AC power source available? Have you tried it on electric?

Check that ECO hasn't tripped and is reset......
Two sets of t-stats. Located in outside compartment. Black cover. Left one is for 120V AC electric element. Right one is for propane. Push/reset.

Post what is does and what it doesn't do.

Sorry, I should have said it is a Suburban SW12DE DSI. It has been working fine for months, now suddenly not working.

Which model? IS this an electronic ignition model? Check the thermocouple to be sure it is clean and in close proximity to the pilot flame.