Mistakenly flying with an expired medical certificate; the pilot of a C421 encountered a false fire warning on short approach and requested CFR equipment. Fears certificate action account the lapsed medical.

Narrative

On approximately a two mile final; the right engine fire warning light began to flicker lightly. Inspected visually; engine indicators and detected no actual fire or exhaust leak indications. Advised tower as a precautionary measure to alert fire crew. Upon touchdown the light immediately went out and remained out. Taxied to ramp and after shutdown and passenger egress; I removed the cowling for troubleshooting and inspection. Found no evidence of exhaust leak or excess heat or fire. Found the wires going to the firewall sensor probe located aft and outboard had two bare spots where the insulation had come off and exposed the wires. No breakage in the wires or other potential defects were noted. Repaired the wires utilizing 3M electrical tape and secured them so as to be clear of any possible chafing or obstructions. Re cowled the aircraft and ground ran with no defects noted. Determined the repair to be airworthy and returned aircraft to service. I am a qualified Airframe and Powerplant mechanic also. After review of flight and self critique I noted that--although I had scheduled a flight physical last week which did not occur--my physical had expired. I would not have made a different decision as to the precautionary call even if I had known of the medical but I am concerned that any repercussion in such 'few days over' honest mistake situation could cause some to hesitate to call for ground assistance for fear of a certificate problem. I take full responsibility for my failure to pick up on this.