Dial is set to off. Why does main burner still light?

Check for error codes and service manual on following link:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

Replace gas control valve
http://waterheatertimer.org/How-to-replace-Honeywell-gas-control-valve.html

Gene:

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If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Hi there.
Check and clean the thermopile, it must be free of soot or any form of dirt so that it can properly sense heat from the pilot flame and generate millivolt to open main valve to fire up main burners.
Regards.

First check and see if the dial on the gas valve is on the ON position. Next turn the thermostat up all the way.if it does not come on then, this sounds crazy, but, tap the gas valve twice lightly with the back end of a screw driver, sometimes a spec of dirt can clog the gas valve and this releases it. if it still doesnt come on, you need a Volt Ohms meter or multi meter, set the meter to millivolts, you want to connect the 2 leads from the meter to the terminals on the gas valve that the 2 wires from the pilot generator, located next to the main burner underneath tank. turn the meter on and the millivolts should read a minimum of 400 milivolts, if lower, replace pilot generator. If still doesnt work, replace gas valve.

Possibly the ignitor for the main oven burner has failed--

An observation question:

When the Broiler 'lights' and comes on, do you notice the ignitor glowing bright, before the gas valve (to the Broiler) opens, and you get the Broiler lighting---

Now-- for the main burner to come on, -- there has to be a similar bright glow from the MAIN BURNER ignitor, before its main burner gas valve can open-- No Ignitor?-- No ignition, and not Main Oven burner!

Let me know what you need from this point on --

Mack B

You probably need a new switch for that burner now . Check the burner before replacing it to see if the burner receptacle is burn't

This is a great unit! Try turning the flow nob to the half way point and the flame all the way to low. Run the hot water tap and slowly turn the flame dial until you hear the unit try to light. Every house is different regarding the restrictions in the plumbing and water pressure. Once the unit tries to light that is your minimum setting. It is best to leave it there.

it's the thermocoupler ( about $20 ) that is bad replace it. if that doesnt do it it is the box with the on/off/ pilot button ( about $175 ) I found a complete unit at www.americanrvcompany.com for $275 plus shipping ($300 total) and that is how i fixed the exact problem with mine.

Thermostat is bad. There is a micro switch behind the dial that reacts to the temp probe and you may try cleaning it out first but in my experience replacing the t-stat is usually required.

Check regulator on the unit.
Check pilot unit on the heater
use soapy water to check for leaks if see bubbles turn off main gas supply valve.
always turn off gas supply before any checks or repairs are made
when all else failes call your local gas provider to check heater and gas supply

If your pilot lights up but the main burner doesn't light up then you have a bad pilot sensor or gas valve