Greetings,
I have an older Carrier 58ss that water from the collector leaked and made its way to the blower control circuit board. We started having a problem with the fan always being on so we called the company we have service the furnace and AC come out. When the guy turned the furnace on the blower control board shorted and started a fire(quickly extinguished). He said it wasn't worth fixing and we should buy a new, but would replace burnt circuit board and wiring harness for $800 if we insisted.
Before I get flamed for being a total idiot who shouldn't be messing with furnaces:
1) I have always had the unit serviced by the same company in the past. 2) The "expert" is the one that applied power to the board after being told of the water leak causing the real fire that smoked the board 3) I don't want to spend $4K for a new furnace 4) $800 to replace a plug in wiring harness and a circuit board that has a dealer cost of less than $100 is IMHO unreasonable 5) I am not a furnace expert, but I can read and understand schematics. I have been an engineering manager at a large electronics manufacturing company for over 20 years including several years managing a circuit board assembly plant.The control board part was HH84AA005 is obsolete, the Carrier replacement is HH84AA021. I also replaced the tranformer(scorched by the flames) and the relay on the inducer board(corroded contacts from the water dripping down). After installation, everything worked except that there was no 24V to the Pick coil (terminal #3) of the gas valve.
While it is supposed to be a drop in replacement(if you believe the docs), the board is significantly different with additional functions and features. One big difference is that 10B1-2 that needs 24V can be traced directly to the C terminal which goes straight to ground through a plated mounting hole on the circuit board. There is no grounding on the old board at all.
Does anyone know if there is a service bullitin with modifications required to make HH84AA021 work in a furnace that was shipped with a HH84AA005? Any other insights would be greatly appreciated.
Thank you very much,
Bob