My water heater will not relight. It is as if it is not getting any gas. Could this be that the heating element is bad

If you're having trouble with the pilot light on your gas water heater, you need to check the thermocouple. It is one of the first things to check when troubleshooting a pilot light problem with a gas water heater. A thermocouple determines if the pilot light is lit. If it's not lit, the gas valve fails if that's the problem, replace the thermocouple.

How to replace Gas Water heater Thermocouple replacement
1. Shut off the gas valve on the water heater and the gas valve on the line near the heater. Remove outer and inner doors, and loosen the pilot and supply tubes and the thermocouple connections to remove the burner assembly.
2. Loosen the screw holding the thermocouple to the bracket. Remove old thermocouple. Bring it with you to the store to ensure you are buying the proper replacement.
3. Install the new thermocouple. Position the thermocouple so that the pilot flame heats 1/2 inch of the tip.
4. Reinstall burner assembly in the water heater. Tighten burner supply tube, pilot tube and thermocouple connections. Tighten thermocouple no more than a quarter turn more than hand-tight.
5. Turn on both gas valves. Check supply tube and pilot tube for leaks with soapy water. If soap bubbles, tighten connections to fix leak. Ignite the pilot light, and make sure the thermocouple tip is heating up. Install the inner and outer doors.

You also can replace the thermocouple with out removing the burner

I am not sure if I nuderstood it right; But "a thermocouple will only function if the pilot light flame is on", then the thermocouple will be heated and detec the availability of gas and open the main gas valve for the burner.

So if the PILOT LIGHT assembly is defective then should we replace the pilot light assembly first? Not directly the thermocouple.

Correct me if I am wrong.

Yes you are correct if your pilot line have no gas and it does'n let and not stay on the thermocouple will not be functioning you need to fix the pilot gas problem first, also Please explain your problem that we can better help you, Thanks.

John.

Correcting...

If you try to light the pilot and it won't stay lit then in most cases, the thermocouple needs to be replaced. If the thermocouple was working it would get heated by the pilot and it would open the gas valve (you have to hold the pilot button in for 30 seconds after you have lit the pilot).

If you can't see a pilot flame while trying to light the pilot then the gas supply may not be there. You would unscrew the union fitting to check for gas pressure in this case.

In almost 95% of the cases like this, the thermocouple needs to be replaced... super simple job and inexpensive. I'd replace the thermocouple, light the pilot (if gas confirmed present), hold the pilot button in an additional 30 seconds and then turn on... should be all set.

Mark

The thermocouple is a bi-metal material. When heated it generates a small electrical current. That small electrical current is what tells the gas valve that the pilot light is lit. Without that small electrical current the gas valve will not open.

Some newer models have a flame sensor and pilot light combined. So you must replace the entire assembly. Older models have thermocouple separate as shown in afaroo's picture. You simply replace the thermocouple.

Sorry Mark we were typing at the same time, and thanks for your input.

John