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BS-36UFF Warning Light


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  • BS-36UFF Warning Light

    Hi all, Anthony here, I have a Toyotomi BS-36UFF water heater. I inadvertently ran out of fuel, and ever since, it fires for 20 seconds, shuts off, then the yellow warning light comes on. I raised the tank about 10-12 inches and added 20 gallons of fuel. I got the Toyotomi Laser 730 heater working fine.

    I bled the BS-36UFF at the fuel strainer many times, and I still get the yellow warning light. After cycling many, many times, the pressure relief valve gave out and needs to be be replaced, which is what I will do today. The relief valve is 150 psi/210 temp. I was thinking of draining the heat exchanger after replacing the relief valve as a next step.


  • #2
    The 25 second timeout is tied to the flame detector. If it doesn't see any flame within 25 seconds, it shuts the startup sequence down & lights the yellow LED. I went through this about 20 years ago.
    Here's a file from Rural Energy in Alaska. They used to have a lot of troubleshooting info, but it's not there anymore.
    Oil Miser 25 Second Warning Lamp.txt


    • #3
      Is the unit firing when you turn it on. You should be able to feel the pipe to see if it is getting hot. Does the fuel pump make a buzzing sound before the yellow light comes on.

      Since this unit is a BS36 it could be 25 years old. Has this unit had a burner service in the last 4 years? By service I mean, burner gun removed and the nozzle replaced. The electrodes should have been either replaced or at least adjusted. Lastly the flame retention head should have been removed and cleaned.

      Be careful of draining the heat chamber. When you flush the heat chamber, be sure to run water back into the chamber to bleed out the air.