This unit is 15-20 years old already. We really started experiencing issues with it after we had it relocated to a different area of our basement due to remodeling. I do believe that a sufficient amount of dust remains inside the furnace; it was not thoroughly cleaned after the basement was finished, however it had been working sufficiently enough. The first issue was the blocked vent safeguard switch constantly tripping after the furnace had been running for a long period of time. Second issue is regarding a part that I can't find in the manual. Looks like some sort of sensor. It's dead-centered within the middle of the upflow duct right behind the gas manifold; has two spade connections on it. After the move, the rehabbers felt the need to jumper those two connectors in order for the heat to work like it should. With the jumper off the connections, the blower would run, but know heat would ever develop. The backing to this sensor is very fragile and has cracked in half. I've had to use duct tape in order to reinsert the piece and keep it elevated in the middle like it was to prevent the sensor from touching the metal sides and shorting something on the furnace out; which has happened a few times already because of this. Latest issue is that the blower will not come on at all. Brand new Hunter t-stat, with Fan setting to ON instead of Auto for testing, clicks and sends the signal to the blower, but it never responds. I've already replaced the fuse on the control board as the lil 3A guy was blown when the sensor in the previous paragraph made contact with the side of the duct. I was not able to find an equivalent at 3am, so I put the smallest of a multipack of fuses in--10A. I'm almost positive I've damaged something by have such large amount of power going thru to components that probably can't handle much. With the economy the way it is, spring around the corner and family finances not where they should be, I'm trying to avoid buying a new furnace as long as possible. Constant research leads me to believe the blower motor or relay on the control board have gone bad. Heck the board itself may have bit the dust. What's a guy to do here?