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Hi, I have an older Bryant 75000 BTU Natural Gas furnace built in 1986 with a HH84AA 011 board. The thing started acting up where after the furnace would cycle the blower would come on briefly for a couple of seconds then turn off about 3 times within about 10 seconds. This had gone on for about a month. Now the blower will not turn off at all. We have to turn the power off to the furnace to get it to shut down. When it gets cold in the house we flip the switch and after the flame goes out and HX cools we flip the switch again. I’ve searched the forum and found a few instances where the blower stays on for this type of system. Here is what I’ve learned and done so far… I was looking for a bad Transformer which is working and putting out 24V. Checked for power between SEC 1 and SEC2 and get 24v. Checked the voltage between R and C and I get 24 volts as well so the board seems good. I cleaned the contacts on the relay and getting a spark when switched on. Checked the upper limit and it seems to be working fine along with the fuse on it is OK too. I disconnected the T-stat wires and tested everything again and everything seems fine. BUT the blower still will not turn off! I started tracing looking for any bare, worn or broken wires or loose connections and everything seems fine as well. I thought I'd have this fixed by now with the info I found on this site (you guys give great info) But this thing is driving me nuts! ANY HELP would be appreciated! Thanks! Jim J