Performed a heating pm on (2) Gas Furnaces. Checked the electrical connections, cleaned the flame sensors. Checked the gas pressures. 1st- 6.8” wc incoming/ 3.1”wc manifold 2nd- 6.7”wc/ 1.7”/ 3.3”wc manifold Started and checked the safeties. Performed a combustion test. 1st- 9.3% o2, 13 ppm, 78.5% efficient 2nd- 11.3% o2, 13 ppm, 94.0% efficient System is operating properly. While performing the maintenance, noticed the 2nd fl furnace did not have a service switch or any way the turn the power off except for going to the breaker panel to kill the power. Installed a 2x4 box, switch and a gas switch plate at the furnace. When the blower turns on for the 2nd fl furnace, there is an arcing noise coming from the relay on the circuit board. Recommend replacing the board before it goes bad.