A.O. SMITH PROMAX WATER HEATER MOD - FCV 40 100 nat . Gas

[ARAGON77]

Hi there I got a A.O. SMITH WATER HEATER MOD - FCV 40 100 , that shuts off by it self after heating for about 20-25 min, I just replaced the thermocouple with the cut off , the igniter and pilot line .

I also tried cleaning the screen under the burner with my vacuum , but it didn't help at all ,

CAN ANY BODY PROVIDE ANY TIPS .... ...?.

[RegUS_PatOff]

what shuts OFF ? ...  the pilot ?

Does the incoming Gas Supply Line have a drip-leg at the Gas Valve ?

[ARAGON77]

The pilot and the burner will shut off at the same time , pilot and burner only stay on for about 25 minutes .

And no there is no sediment. Trap at the gas valve inlet . I just put in a brand new thermocouple

[Budget Appliance Repair]

It's not the thermal couple pilot assembly most of the time on these units.

 

Mostly always a plugged flame bearer ceramic disk that is plugged from not being maintained.

 

If you just ran a vacuum, (how you got it thru the little 3/4" x 5" slots I don't know), around with a crevice tool maybe - that's not enough.

 

You really need one of these: http://www.tightspotvacuum.com/ to clean them properly and sometimes if it hasn't been maintained for many year and no one ever installed the LDO (lint-dust-oil) screen, even that won't be enough and you will have to remove the burner assembly and flush with water from the top side while vacuuming from the bottom side to remove all the lint and dust that is accumulated/packed in the hundreds of little holes.

[RegUS_PatOff]

[ARAGON77]

A big thanks to all for these useful tips , I'm going to try cleaning this lint ,oil screen and hopefully this will solve this problem . Once again thank you all for your help

[Budget Appliance Repair]

Ref#11 is the LDO screen that needs to be used, (NOT LEFT OFF like you find so often with these units), you need to make sure the plastic LDO screen is clean but that isn't where the blockage usually occurs, (because it get left off most of the time).

 

Need need to get into and clean the ceramic disk under the burner, inside the air inlet openings that the LDO screen covers