They were quick to come out and diagnose the problem with my furnace, but I thought the estimate of $549 a bit high to replace the circuit board. So called around and found Leo's Appliance in Concord that sells appliance parts and the circuit board was only $90.49 - that is the retail cost to me, so I imagine the wholesale cost is a lot less. So BEWARE of this company since they wanted $500!!! to replace the circuit board which is located right in the front of the furnace - extremely easy to access. I hate it that you cannot trust repair companies.
Reinstall the access panel and disconnect block. Turn on the circuit breaker and furnace switch. Then set the thermostat to a lower temperature and wait for the AC to start (see “Be Patient at Startup,” below). The compressor should run and the condenser fan should spin. If the compressor starts but the fan doesn't, the fan motor is most likely shot. Shut off the power and remove the screws around the condenser cover. Lift the cover and remove the fan blade and motor (Photo 7). Reinstall the blade and secure the cover. Then repower the unit and see if the fan starts. If it doesn't, you've given it your best shot—it's time to call a pro.
In the United States, HVAC engineers generally are members of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), EPA Universal CFC certified (for installation and service of CFC HVAC devices), or locally engineer certified such as a Special to Chief Boilers License issued by the state or, in some jurisdictions, the city. ASHRAE is an international technical society for all individuals and organizations interested in HVAC. The Society, organized into regions, chapters, and student branches, allows exchange of HVAC knowledge and experiences for the benefit of the field's practitioners and the public. ASHRAE provides many opportunities to participate in the development of new knowledge via, for example, research and its many technical committees. These committees typically meet twice per year at the ASHRAE Annual and Winter Meetings. A popular product show, the AHR Expo, is held in conjunction with each winter meeting. The Society has approximately 50,000 members and has headquarters in Atlanta, Georgia.
Before opening the electrical cover on the A/C unit, be sure to shut off all power to the compressor unit and the indoor furnace or air handler, and verify that it is off. Note that this may mean shutting off a circuit breaker that serves the furnace and air handler, and then, near the compressor, pulling out the disconnect block (or shutting off the 220-volt power) to the outdoor compressor.