True use of anything goes - NG furnace problems

Any HVAC guys out there I could use some advise, I have a late 80's early 90's Bryant Plus 90 furnace that has been giving me problems. Furnace keeps cycling on & off, relays on the main control board rapidly open & close intermittently. I beleive it to be related to the inducer motor circiut, I paid some clown to come out & fix it a few weeks back he replaced the inducer circiut board & flow switch assm w/ a used part(and charged me for a new inducer motor; bastard). Last night it quit heating altogether so I played w/ it from 3am til' 9am this morning. I unplugged & plugged back in all the connections on the inducer circiut board & the furnace worked normally for a few cycles then acted up again. I replaced the inducer motor w/ the used assm the guy left behind. It is working better now but still not right. The water trap is clear, the intake tube is also clear & unobstructed. Should I looking @ replacing circiut boards or is there something else I should be looking @. I'd pay a "professional tech" to come fix it but I'm finding the local idiots to be better salemen for new furnaces than technicians being able to fix an electrical problem on an otherwise functioning unit. I don't like wasting money on people that don't do the job they where hired for. That said I am going to replace the furnace, but can't afford it just yet. After xmas I will be able to swing it so I just need to make it work until then. I was going to sell the VFR to help offset the cost but I don't like that idea much. Any help appreciated, or a trouble shooting book/wiring diagram etc appreciated even more.

 

An HVAC question....now that's got to be a VFR World first! Bummer the VFR might have to be sacrificed though, sorry to hear that.

 

Gee, kind of hard to TS this online. Those Bryant 90s were sometimes a lot of trouble. Are you sure that the intake is clear, I've seen really small obstructions like a little mud wasp nest mess up the air flow. Is the tstat a setback model? Old batteries cause a lot of trouble. The flow switch could cause the relay clicking you mention. Did you try jumping the switch? You can only jump the switch after the inducer motor starts. I guessing its not the board but something else. Did you try adjusting the flow switch? Most have a small allen in the middle, they can be adjusted to switch with less pressure. Try adjusting this first.

 

Thanks, I'll give it a shot; after hunting season. seems to doing marginally ok for now.