Performed heater tune up. System is 33 years old, Heil furnace. Temp rise and gas pressures are within specs. Blower wheel needs cleaning. Performed hydro scan on heat exchanger. Found 5 breaches. 1 breach in left exchanger and 2 each on the middle and right exchanger. Located in the back where the bends are. Also found 2 screws on face plate of heat exchanger striped and not screwed in. Rust all around face plate and inside heat exchanger as well. Highly recommend not using heater. Recommend: Replace unit due to breached heat exchanger.