I called Cardinal when our AC wasn't working. They diagnosed the issue -- a bad control panel, which would cost $500 to replace -- and we discussed replacing both the air and the furnace instead, since both were 19 years old and showing other signs of aging. Several difference scenarios were presented to me, with various options for rebates, discounts, etc.

While our family discussed the issue, they put in a new control panel so we had working air. We ended up replacing both. The workers came on time, worked efficiently and cleaned up after themselves. They also emailed me a YouTube video about the new thermostat we selected. All around a positive experience.