Honestly, 90% of all the problems we run into are caused by dirt or electrical problems. If your equipment is dirty, it will no longer function properly and may even quit running all together. The best way to clean your coils is by first using a hand-held whisk broom to remove surface debris.
Then, if possible use water under moderate pressure (not too much pressure, or you will bend all your fins over and have bigger problems) and spray the coils out.
Generally, you don't have to be concerned about using water. Just don't spray directly on electrical components. If you still can't get your coils clean, you may need to call us to use special chemicals and equipment to clean them for you.
For air conditioning and heat pump equipment, it's easy. At least twice per year, spray the outdoor unit's coils with water and rinse them clean. Inside, keep your equipment's filters cleaned or changed on a regular basis. If your equipment is located in a particularly dirty environment, we sell filters that wrap around the outdoor unit to catch the dirt before it can get to your coil.
For refrigeration equipment in a restaurant, bakery, or convenience store, buy some cheap furnace filters from the local hardware store and fasten them to the intake of your coils to catch the dirt, dust, and especially grease.
First of all, if you are using propane, make sure your tank is above 20%.
Another very common problem is furnace vent pipes that are iced up or otherwise plugged. Especially in extremely cold weather, frost can form in your PVC pipes where they exit the house. Check the pipes, and remove frost if necessary.
Finally, power-cycle your furnace by turing the power off, waiting 10 seconds, and then turn it back on. If the furnace still fails to work, you will need to call a professional to help you out.