water heater won't light when raining or damp

If it is an Atwood, I would suspect a dirty or cracked spark probe assembly? In the manual it will tell you how to check the integrity of the spark probe. If you can hear the spark then I wouldn’t suspect a bad board. Basically when it is dry out, you turn the gas off and insert an insulating material between the sparking and ground probe gap and this might force the spark to jump where it would if it is damp out? If you do it when it is dark out, it would be easier to see the spark.

Wasn't the OP asking about a water heater not a fridge?

I had the same problem with a Dometic fridge. The issue was a bad igniter electrode. I replaced it, but then heard you can clean the ceramic with sandpaper then spray it with a clearcoat urethane to bring it back to life.

donn0128 wrote:
Bad igniter board from your description.

It could also be a cracked porcelain on the igniter electrode itself too. It sounds like the board is creating a spark, possibly to ground.

On mine, I got a log lighter ready. This procedure is best done with 2 people. One person is inside the rig and turns the fridge on. The other person is outside with the fridge cover off. When the gas valve (solenoid) opens- stike the log lighter and get the flame right up to the burner orfice...it will light. Once this happens the fridge will work normally. What happens is the ignitor gets wet and won't spark. This can happen alot and did on my rig. You might try parking it differently so the fridge side is not in the wind direction, or rig up a temporary cover to go over the fridge cover outside.

Bad igniter board from your description.