The blower on the heater seems to be a key element.
You need to have it officially oiled so that nothing wears out or is disfigurementd. The blower belt can be worn & you can sustain some injury with use. It is an pressing, costly part of the system that must be treated with love. Why am I telling you this? I didn’t treat my blower with respect. I procrastinated & never called for Terrell heater service. I figured if my heater turns on, then it is fantastic to go. The most I did was change an air filter. It consistently turned on so I figured all was well. Then my heater started making noises when operating. It was a horrible screeching, squeaking sound every time. It was impossible to sleep, work, or exercise with that racket. I then realized that my minor cleaning duties weren’t going to service it. My heater never magically fixed itself either. I called the Terrel heater repair provider & the guy was actually distraught with the condition of my blower. There were worn parts, frayed belts, & all sorts of debris on it. The disfigurement was extensive, he said. He also told me that I needed to replace the entire blower & the belt affixed to it. It was such a hefty repair. I truthfully debated on getting a whole up-to-date heater. When you factor in the price tag & what you get, it was a smarter option to replace. I chose repair though since the thought of starting fresh was disheartening.