[gasmanobt3]

My neighbour has a clare brothers furnace. Model HEMI 70BD. I replaced the module for them because it was shot. The furnace fan now runs on low speed all the time and during the call for heat then goes into high. T-stat is about 18yrs old. Mercury switch. The humidifier and EAC are wired together and come on when the humidifier is turned up. Is there a bleed or bad relay somewhere that I may have missed? The fan should quit after cool down. The fan does slow but doesn't stop. Also the high limit is new. I traced the wiring schematic and am stimied at this point.

[KC13]

If this isn't a variable-speed unit, check the blower motor connections at the circuit board to see if one of the leads is connected to a terminal intended for continuous blower operation. Have you tried disconnecting the thermostat wires from the furnace control board, to see if blower still runs? If it doesn't, something in the control circuit is demanding blower operation. If it is variable-speed, and it still runs, try this: with thermostat wires disconnected from control board, door interlock switch taped in (if present), and power "ON", jumper "R" to "G" at board to initiate blower operation. Wait for blower to start and reach running speed. Remove jumper for 1 second, then reconnect. Does blower speed change? If so, repeat until low-speed operation is observed. Remove jumper, turn off power for 1 minute, then back on. Let us know if this corrects the issue.

[gasmanobt3]

Thanks. It is a variable speed motor. Goes from slow speed to high. I'll try that. One of the other techs I spoke to at work said it could also be constantly running because of its design. I find it unlikely though. Any thoughts?

[KISS]

Here is some info from hvac1000 on Clare: https://www.askmehelpdesk.com/heatin...al-250186.html

Some furnace control boards have dip switch setting to set the fan speeds etc. Did you transfer that information?

Next, I'd look for labeled jumper locations that you may have missed.

Selectable by design is certainly possible. Jumper or DIP switch.

[T-Top]

Have you checked to see if your humidistat is bringing on the blower.