I have a Dayton 3E290 wall heater that was installed new 30 years ago. The pilot light started to extinguish a few years ago. Gradually this began to occur more frequently. I've changed the thermocouple, which did not keep the problem from getting worse. Now the pilot light won't stay lit at all after I release the button.

If it is a wall unit, it has an over temp safety switch which is most likely tripping from dust preventing proper airflow across it . A good cleaning should cure this.

The pilot flame heats a thermocouple, so if the pilot goes out, the thermocouple cools and shuts off the gas. It can take anywhere from 20 seconds to 2 minutes for it to shut off. You should hear an audible click when it happens.

There are two types of igniters, spark-type or glow heater. The glow heaters wear out and crack or break and the spark-type spark gap gets fouled or dirty. Both could have electronics problems that drive the glow heater or spark systems. The Filtrete thermostat is not the issue. While rapping the unit makes the glow igniter come back together to glow again.

Find where the gas line connects to the gas valve on the back of the heater, from the gas valve, follow a small aluminum tube going into the back of the heater. There may be a removable door to access the pilot assembly. If there is no aluminum tube, the unit has electronic ignition and no pilot lite. Turn the gas knob to off, then to pilot. Hold the gas valve in and with a long match or gas grill lighter, light the pilot. Continue to hold the knob in for about 30 seconds. After that, release the knob and check to make sure the pilot stays lit. If so, rotate the knob to ON. The thermostat will kick the burners on.

it sounds like the afc the fan control not working could be dust on the afc

not hard but before replacing check pilot light and thermocouple for proper function and setting if pilot light not in right position thermocouple wont open gas valve if electronic ignition check for power and proper gap on igniter also check stat for proper function

sounds like when burner kicks in it is diverting gas away from pilot. you have either too low pilot heighth or more likely an obstruction in pilot assembly

Hi i would say get a gas fitter to do this its not as simple as it looks

Normally you turn the gas valve to the pilot position, light the pilot, hold down the gas valve knob for 30-40 seconds and release. If the pilot will not stay lit replace the thermocouple. These are available ay Home Depot.

Ray

A clue to what could be wrong is that you mentioned it took 10 minutes for the pilot to go out. It could be your gas valve. Get a technician in to check your gas pressure both before the gas valve and after. Have them check it as the water heater is running.