Help! #3 error. Replaced high limit and low limit switches. Still get #3 error. Control board right? Replaced cb and rewired new harness, new board doesn't even power up but exhaust blower comes on high. Put old cb into new harness and I get the same problem, #3 flashing. I did noticed that the exhaust blower cooling fan comes to a stop but I can hear the impeller still rotating. That's not good. The gray wire are connected to the vac switch, brown wire connected to the low limit and the orange connected to the high limit. About ready to punt.