Ive got two Carrier Furnaces Model 58tx155---11120 twinned together and having an issue with the blower relay on the primary unit chattering. The only thing that gets it to stop is pulling the wire that connects the two units. Both work perfectly fine individually but when connected together I have the afore mentioned issue . Figuring it was the primary units control board I replaced it but the problem is still there.Spent most of the day today getting beat up by this problem today an help would be appreciated. Thanks