BRADFORD WHITE 40 GALLON ELECTRIC WATER HEATER MODEL M240S6DS-1NCWW.. PROBLEM : I WAS ONLY GETTING A FEW GALLONS OF HOT WATER FROM HEATER. FIGURED ONLY TOP ELEMENT WAS HEATING SO BOUGHT TUNE UP KIT AT

It is pretty easy - make sure gas valve is open, change control know to pilot. Press the ignitor a few times and once pilot lights up switch control to warm or hot position.

See instructions by downloading manual for MI-403SF6BN from this site
Bradford White Water Heaters Built to be the best

Sounds like water leak.
For example, broken pipe... or water running out of TP valve.
That would explain variable hot-and-cold water at tap.
Turn off all taps, and observe if water meter is registering water usage.

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First check the power make sure that is working if it is replace one or both elements. makes sure you match up the watts and voltage

http://waterheatertimer.org/Low-hot-water-pressure.html

Gene
h

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

Call Bradford White or installer

Gene
h

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

1) Copy following links:
http://waterheatertimer.org/How-to-adjust-temperature-on-water-heater.html
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

2) if you have electric water heater, and too much hot water, then thermostat may be bad, or element is shorted and needs replacement. Test elements first, and if they're ok then replace both thermostats.

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

Water heaters are a huge field of knowledge. Problem is not 100% clear.
There is a resettable thermal switch on the combustion door. This switch is round and has two wires that come from gas control valve. Thermal switch trips when combustion parts have not been cleaned and they cause overheated condition, or sensor reads temperatures above 180, or thermal switch has gone bad, or gas control has gone bad.
http://waterheatertimer.org/images/Whirlpool-Resettable-ECO-8.jpg
Add a comment with more information for continued help.

1) Bradford White support:
http://www.bradfordwhite.com/supportserv.asp

2) Bradford white mi403s6fbn is 6-year-warranty 40 gallon tank-type gas water heater with Icon electronic gas valve, and atmospheric venting.
Older models have the dial-type Robert Shaw or White Rodgers gas valve.
Open following link to see age of Bradford White:
http://www.bradfordwhite.com/findaserial.asp

3) Bradford white has 'product manuals' and 'service manuals' on following link:
Product manuals have general information and advisories that people can read about water heaters.
Service manuals are for plumbers and technicians, and do-it-yourselfers for testing and repairing water heaters.
http://www.bradfordwhite.com/documentation/residential/gas.asp

4) Typical manual for your product shows different gas valves, lighting instructions, and advisories, and troubleshoot checklist:
http://www.bradfordwhite.com/images/shared/pdfs/manuals/238-44219-00J.pdf

5) Add a comment with following information if you want specific help with servicing water heater.
What are you trying to reset on the water heater?
What are the symptoms, and what have you noticed, and what have you tried so far?
Which gas valve does your water heater have? Please open typical manual and view images of the three basic gas valves.
When was water heater last serviced and cleaned?
How old is water heater?

Take a moment and rate answer:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

replace upper thermostat, and hi temp limit, usually made in one piece, also make sure the new stat is pushed up tight to the tank when you install it.

turn the power off and flush it out by letting the tap run for an hour or so
i think it could have lime scale in it or the element is about to blow if its the type that you can get the top off look inside it you may see the fult even kettle cleaner may be needed to clean it out, but dont go drinking that water???