Water heater won't stay lit with propane?

I know this may sound silly but it happened to me when I was new.
I thought my flame was going out or not lighting when it was supposed too, but my water was still too hot from the electric rod.
My electric thermostat switch was set higher temperature than my Gas side was, so that the gas would only run when the electric was not keeping up, but when I would turn the gas off and then back on it would sometimes light for a few seconds and then go out.
This probably is not it but might think about it.

Allworth wrote:
An electrode starts the flame; a thermocouple determines whether or not it is fully lit. Both are part of the ignition system.

Not with a DSI ignition ....no thermocouple

Main flame generates a milivolt signal via flame ionization.
That signal goes back to circuit board 'proving' main flame has lit/staying lit. Circuit borad then keeps power on gas valve

RV Spark Electrode


RV Thermocouple (some use an ignitor)

An electrode starts the flame; a thermocouple determines whether or not it is fully lit. Both are part of the ignition system.

Lets not confuse OP.
A combo water heater with DSI uses a spark electrode not a thermocouple

Clean the thermocouple end with a BRASS brush and make sure it's positioned directly in the flame.
Thermocouples rarely go bad, they just get sooted up.

Try cleaning out the burner tube (compressed air or small bottle brush). All it takes is a spider Web to disrupt air/gas flow. If that doesn't work, remove thermocouple in the burner and clean it off using sandpaper.
One of these has always worked for me.

Thermalcouple in burner needs replacing?

Thanks guys I'll do what you suggested. It does light and stays on for about 4-5 seconds then goes out but a few times it does stay lit and heats.

Water heater is attempting to light.....but main flame is not being 'proved' so power drops off gas valve and it closes.
It will make 3 attempts and then 'locks out' (Turn ON/OFF switch OFF to reset)

Spark electrode is either sooted up.....needs cleaned
Main flame is not engulfing tip of electrode.....needs repositioned
Weak spark/main flame not lighting.........check grounds. Check ceramic for cracks. Check wire connections on spark electrode and board
Main orifice plugged causing low gas flow....clean orifice
Burner tube obstructed......clean tube


In short.....like suggested above clean burner assembly & orifice

Have you tried cleaning the burner assembly and the orfice