Product review (5 stars): This part fixed my Trane furnace that my now-former HVAC company wanted $510 to replace
Have a 1988 Trane HP furnace with a fan that would not shut off unless the HP ran a full cycle.  In other words, if I lowered the thermostat or switched the system off the fan would keep running indefinitely, and sometimes wouldn't shut off if the weather was mild and the heat pump ran a short cycle.  The fan relay board was the obvious culprit and was easily replaced once I realized that Trane hides this relay inside a small silver box that looks almost too small to hold it.  I did take the time to label the leads before removing them from the old board, as the tight space in the box meant the sequence of switching leads made it easier to disconnect more than one at a time.  If your older Trane furnace fan is stuck in the on position, this is a pretty easy repair.

My HVAC company that I've used for 15 years wanted $420 to replace this...  Oh, plus a $90 diagnostic charge, even though I told them that this part was the problem over the phone. They claimed they were replacing two parts (charging separately for the relay and the board) when they have been combined on this updated part for years.  I understand the cost of doing business (I owned my own business for 25 years) but this estimate was unconscionable.