My manufactured home has central heating/cooling with a Nordyne/Intertherm model MGHA-056ABFC-05. I just changed the blower motor, replacing the GE motor with a matching Dayton motor. All the wiring (red, black, white, blue) seems to be identical. The blower is working fine, but now the A/C unit behind the home has stopped working. What is the blue wire for? I do not believe that it was connected to anything on the old one, and I do not see what it might possibly connect to within the wiring box. Wiring diagrams on motor and on front panel of unit indicate that blue is for "medium."

The unit outside does absolutely nothing, as if it were a fuse. The blue line coming from the blower motor is a hot wire, and I was wondering whether it could be power supply. I also wondered whether the problem may relate to the ventilator switch, which has 3 settings(on, off and fan)

One question did you change the motor on the air handler or the condenser outside.

Check you fuses... the blue wire probably indicates that you have a two speed fan motor.

Thanks. I changed the blower motor on the unit inside, that circulates the air inside the home. The blue wire is marked medium(red is marked high and white is marked low). The heat exchanger outside A/C unit does not do anything at all when the thermostat kicks the new blower on. I have pulled the fuses and will see if replacing them helps. I don't know how to tell if those big fuses are blown or not. So the blue wire does not have to connect anywhere then, since the unit is single speed, right?

So the blue wire does not have to connect anywhere then, since the unit is single speed, right?

Just tape it off.

My manufactured home has central heating/cooling with a Nordyne/Intertherm model MGHA-056ABFC-05. I just changed the blower motor, replacing the GE motor with a matching Dayton motor. All the wiring (red, black, white, blue) seems to be identical. The blower is working fine, but now the A/C unit behind the home has stopped working. What is the blue wire for? I do not believe that it was connected to anything on the old one, and I do not see what it might possibly connect to within the wiring box. Wiring diagrams on motor and on front panel of unit indicate that blue is for "medium."

The unit outside does absolutely nothing, as if it were a fuse. The blue line coming from the blower motor is a hot wire, and I was wondering whether it could be power supply. I also wondered whether the problem may relate to the ventilator switch, which has 3 settings(on, off and fan)
The blue wire is also a ground and need to be grouned to the fire wall.

;)
The blue wire is also a ground and need to be grouned to the fire wall.

Cap the extra wire off. I think you need to start by looking for loose connections, it's possible that you pulled something loose while changing the blower motor, start with low voltage connections.

;)
Grounding the blue wire is a good way to burn the motor uo blow a fuse and /or get a great shock

You have probably got your unit running by now but I wanted to tell you that if you do need fuses make sure that you buy an expensive fuse. They have to be a dual action fuse to work on your condensing unit and the cheap one will blow about the firs time you turn it on. By cheap I mean ones under five dollars.

And DO NOT connect the blue wire to ground that is a second speed for that motor,