My control panel displays a flashing FUS message. I take this to mean "fuse" but I cannot find a fuse anywhere. My RD-900 is at least 13 years old. Perhaps close to 20 years old (the approximate age of my house). There is no fuse on the wiring panel above the 24VAC terminals -- as appears in the owner's manual of what I take to be the current RD-900 model. Thanks for your help.

Phil Service

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