I have a 2-way fridge in a 1991 scotty, runs good on electric but when i try gas the pilot lights but when the main burner goes to light it just goes out with a noise. Any ideas on the problem.

Tankless?... call service technician

Tank? clean arrestor screen, replace gas valve thermostat
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Gene

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After burner on did you hear any spark ignitor if that your flame sensor is dirty or need to replace....good luck

What are you expecting to happen?

I assume the water heater and water inside it is cold (otherwise you would not be lighting it). You light the pilot. The main burner comes on and the pilot lights it. The main burner should stay on until the tank is hot, When the tank gets hot the main burner should shut off but the pilot stay on. If you draw hot water, cold water will run in and cool the tank. If yu do nothing the tank will eventually just cools off. then the main burner should come back on to reheat the tank.

The thermocouple may have failed. It looks like a copper wire that goes from the gas valve and leads to the pilot light.My first thought is that the pilot light burner is not burning hot enough because its got dust in it or a spider web blocking some of the air it needs to burn hot. If the pilot stays on long enough to bring the main burner on, a dirty main burner lighting rough will cause the pilot to snuff out. To do the actual repair I would suggest that you contact the manufacturer on the internet. Getting up to your elbows in a gas appliance without professional help is asking for dangerous serious trouble. Good luck.

try cleaning the pilot sounds like its a short pilot and when the burner comes on it pulls the gas from the pilot light .

You need to replace the thermocouple.
When you light the pilot it is supose to heat the thermocouple.
the thermocouple produces a small electric current which allows the gas valve to open and keep the pilot going. and allowing the main burner to come on.

replace the thermocouple. it is a small copper tube that screws into the gas valve and goes to the pilot assembly. a good haedware store that sells heaters will have one. they come in various lengths 18"-48".

take millivolt reads while main burner is on.i suspect you will see a drop in voltage until you get to point where it will no longer operate burner(around 200mv).if this is the case you probably have poor pilot characteristics due to dirty pilot,pilot out of adjustment ,obstruction or insufficient gas pressure

I would change the thermocouple and here is why:

The thermocouple is the pilot's, well, co-pilot! It is the electronic device that senses if the pilot flame is hot enough to sustain burning the gas fuel from the burner. If the thermocouple thinks it's safe, then it keeps open the main gas valve located in the pilot assembly. If the thermocouple does not sense enough heat from the pilot flame (such as when the pilot is out), then the thermocouple shuts off the gas valve to the burners.
How the Thermocouple Works
So what is this thing and how does it work? Well the thermocouple (technically called a thermocouple junction) is a device that contains two metal wires welded at the ends and placed inside a protective metal case. The thermocouple sensor is found at the business end of the pilot flame and is designed to be placed in the hottest part of the flame. The other end is connected to the pilot valve body. As the thermocouple heats up, it produces a small amount of electricity and when it gets hot enough from the pilot, send a signal to open the gas valve by using a solenoid operated by a 24 volt transformer. The thermocouple calls the shots, and by converting heat to an electrical signal, it allows the gas valve to open or close. Once the gas valve is open, gas is then constantly supplied to the pilot and as required for the gas burners (as called for by the thermostat). If the pilot goes out, then the thermocouple gets cold and produces no electric signal to open the gas valve's solenoid and the gas valve shuts off the gas supply to the pilot and burners