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Scubadave · 12-11-2007, 05:39 PM

Have a Hydro flame 8940-111 that at times upon startup the fan will come on and then the gas will ignite. After 5 seconds the gas goes off for about 10 seconds then it ignites again for about 5 seconds then the gas goes off again for about 10 seconds. It then relights for 5 seconds and the gas shutoff valve takes over and shuts off the gas for the rest of the cycle. Recycling the therm will produce the same results. Pulled off the outside cover and checked the connections to the board and the furnace ran as it should. This first happened back in Sept when we wanted to take the chill off. Moved to a dryer and warmer area and the furnace worked fine until this morning when it did the light, go out, relight thing again. Tonight it is working just fine

Since the humidity was high this morning, as it was back in Sept, was wondering if this could be possibly be caused by a cracked circuit on the board getting moisture in it? Do I need to replace the board or is there some other cause?

Thanks

chasfm11 · 12-12-2007, 02:58 AM

Atwoods are designed to "flame sense" using the igniter. This means that the board is using the igniter to verify that a flame is present to allow the gas to continue to flow. It sounds like yours might have a problem with this. A possible cause (and a lot cheaper than the board) is the igniter itself.

First, clean the board contacts with a pencil eraser and see if that helps. The next step would be to physically check the igniter to see if the ceramic is cracked. I'm not familiar with your model 8940 but on my 8525, getting to the igniter means shutting off the propane, bleeding the system with the stove time (mine takes several minutes) and then disconnecting the gas valve. If I had your symptoms and had access to the part, I might try a new igniter after having gone through so much trouble to get to it.

Perhaps Mike or one of the other more experienced guys than me has different or better ideas. I've worked on my two furnaces enough to be able to just about be able to take them apart in my sleep but haven't seen other models.

Charlie

Workshop · 12-13-2007, 03:03 PM

Here is a link to Atwoods troubleshooting guide. The page also has a operation video that is helpful. Worked on circuit boards in the Navy, was rare to have a broken circuit run on a board. As was stated earlier, clean and check connections on the board. Does sound as if the board isn't detecting a flame. Which might indicate at least that part of the board is working.

The video will help guide your troubleshooting.