Goodman furnace repair. Upon arrival burners were cycling on and off repeatedly. Checked flame rod reading, 0.1-0.2ua. Pulled and inspected flame rod, heavy buildup on it. Cleaned off and reinstalled part, checked readings again, 2.0-2.2ua. Furnace is working safely and efficiently at this time. Recommend yearly maintenance on furnace due to age (16 yrs old) Found no other problems or concerns with furnace during service call.