I HAVE A RHEEM PVS50 HOT WATER TANK IT ABOUT 6 YEARS OLD AND LAST NIGHT IT JUST STOPPED WORKING. I UNPLUGGED THE UNIT AND PLUG IT BACK AGAIN I CAN HEAR THE MOTOR ON TOP WORKING AND CONSTANT TICKING BELOW BUT IT WON'T IGNITE. AFTER A W HILE THE TICKING STOPS AND THEN IT STARTS AGAIN BUT IT WON'T IGNITE. I SHUT OF THE GAS AND TURN IT BACK ON AGAIN BUT NO LUCK. COULD IT BE A BAD THERMOCOUPLE. THIS MODEL IS SELF IGNITING..