I have a Bryant Plus 80V furnace (model # 315AAV0). I am having an issue with getting the fan go to high speed when using the Continuous Fan mode. I have the dip switches set to have it run on the highest setting and it still only spins at the lowest speed. Also about every few days the 3 amp fuse on the control board blows!

Here is a brief discription of what I am doing. In the winter I use an outside wood "water" furnace to heat water and then run it through a radiator which is mounted just above the A coil in the furnace. I turn down the house thermostat (the one installed with the house furnace system) and use an additional t-stat for the water system. I then tied into the G and 24 V com terminal on the control board of the furnace. Using this system worked all last winter flawlessly and up until about one month ago. I was working on the outside wood furnace so I switched the t-stat to off while the water temp would be cool. Then in a few hours I turned it back on the blower fan was running only in low, and it has been this way ever since. If I run the furnace/heat pump the fan goes to high as designed?? Any help would be great. Is it a control board??

Thanks

Your going to have to trace down the short. Its not uncommon for the 24v coil on the relay to short out or the thermostat wire going to your wood burning furnace. Remember the fuse in the control board is sized for the load of the furnace and A/C no extras. If you start adding controls the fuse may blow. Never replace a smaller fuse with a larger fuse it will only make you buy a brand new control board $$$$.