We have a Trane XL 80 (model TXC037C4HPCO, serial R435RF05G, mfg 10/2000) that was working well, used primarily for the aircon function until we got 16 inches of water in the basement. The water level got about midway up both the large circuit board and the blower fan motor. The fan and motor shaft spin freely. The unit was not on when the water hit. There are no visible signs of sparks or burns from a short. When power is turned on to it the thermostat on the wall comes on normally but there are no signs of life on the unit itself. On the back of the lower door to the unit it mentions a 5 amp fuse but I did not see where that is located. Could it be just a fuse or a dead circuit board and motor or something else. I think it is a White-Rogers board. The replacement procedure looks fairly straightforward. Any advice on the best way to proceed?

 

The 5A fuse is probably for the 24VAC transformer. To confirm that you have 24VAC, with the thermostat turned off (not calling for heat or cooling), measure the voltage between the R & Y terminals at the thermostat. You should measure ~24VAC.

When you set the thermostat for cooling, does the outside unit turn on? When the thermostat calls for cooling, it sends 24VAC to the Y terminal, which connects to the outside unit, enabling the contactor (relay) in the outside unit. If the outside unit does turn on when the thermostat calls for cooling, don't leave it running for more than a couple of minutes, as it will freeze up without the blower running.

 

Replace the unit. The repair cost will be close to a new unit price.