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Toyotomi OM122 and OM 128 water heaters started life as A models. Now they have advanced to B models. In the process some parts have changed and some of those are not interchangeable.
The main circuit board, flame sensor, Ignition transformer, power transformer, and air pressure switch have changed. The A model unit will not accept B model part.
The only exception is the air pressure switch. The switch on the A model is no longer produced. The B model switch can be used in both units.
The main circuit board, ignition transformer, power transformer, and flame sensor for B models will not work on A model units. The A model parts are still being produced and have different part numbers than the B model parts.
Be careful ordering these parts for OM 122 and OM 128. Get the correct part number when placing an order for these parts. An incorrect part that is opened may not be able to be returned to Toyotomi. An electrical part that is opened can not go back into inventory, as its serviceability would be in question.
A more complete explanation for this can be obtained by reading the Toyotomi Service Bulletin: "OM122/OM128 Water Heaters Type A versus Type B Parts." This bulletin can be downloaded with a simple web search.
Tom
The main circuit board, flame sensor, Ignition transformer, power transformer, and air pressure switch have changed. The A model unit will not accept B model part.
The only exception is the air pressure switch. The switch on the A model is no longer produced. The B model switch can be used in both units.
The main circuit board, ignition transformer, power transformer, and flame sensor for B models will not work on A model units. The A model parts are still being produced and have different part numbers than the B model parts.
Be careful ordering these parts for OM 122 and OM 128. Get the correct part number when placing an order for these parts. An incorrect part that is opened may not be able to be returned to Toyotomi. An electrical part that is opened can not go back into inventory, as its serviceability would be in question.
A more complete explanation for this can be obtained by reading the Toyotomi Service Bulletin: "OM122/OM128 Water Heaters Type A versus Type B Parts." This bulletin can be downloaded with a simple web search.
Tom