Enbridge flagged my furnace and shut off the gas. It read 1 degree higher than the year before, which was ok. I was gettting their so called cleaning every year. Another time Enbridge took 4 days to get a part after first telling me I needed a new furnace. When I said that I could get the part in two hours suddenly the part arrived and Enbridge fixed it. It was a cold late November. I never trusted them again. This time I asked for a second opinion about the furnace overheating and yes, it was too hot. Rather than try to sell me one they took the furnace apart, took the blower out and hosed it down and then cleaned the heat exchanger with coil spray and twice with an air compressor. My old furnace has been working like a charm ever since and I would recommend that everyone read and follow your furnace manual, but most of all have these guys come in and clean your heat exchanger because that is the part when it dies you have to get a new furnace. The workers were really knowledgeable and persisted in trying to extend the life of my furnace. So, I would highly recommend that you bring them in and get a full system cleaning at least every five years and then a regular cleaning once a year. I was really impressed because they went beyond and did not try to sell me a furnace. I can't say enough of how pleased I am.