Receive the call that the furnace that handles the lower section of offices keeps tripping the safety, upon arrival I've removed and replaced the oil nozzle. There is a lot of black buildup on the electrode assembly and on the draw assembly which is telling me the furnace is not burning properly. The air inlets for the combustion air on the airband or severely plugged with dirt and dust, I tried to clean them out as best as possible. The fuel filter that is being used on this burner is no longer available locally, I will need to upgrade it to a more modern style filter. I will also need to replace the CAD cell I as it is not sensing the flame when the burner ignites. Also found that the furnace is shaking a lot when the blower comes on, we will need to get a new blower wheel and blower motor as it appears that the bearings are damaged and due to the dirt buildup on the wheel it is out of calibration.