Topic: 66 underdash AC wiring

[e093116]

I'm restoring a 66 AC unit.

During testing of the AC blower motor and 3 speed control switch, I discovered that the motor only works on high speed.  Wondering if this is normal for a bench test of the motor and control switch, or if the switch or motor is bad.

I have restored a 65 AC unit, and it is quite obvious that the switch has two resistors that are used to reduce the voltage to the AC blower fan motor to give it 3 speeds.  The 66 switch that I have is different (has 5 wires going to it instead of two) and also the motor is three wires plus a ground wire, so it is also different than the 65 AC blower motor (which only had two wires).  Since there are not visible external resistors present, I wonder if the resistors are built into the switch housing or inside the motor?  I reviewed the 66 AC wiring diagram and it does not show the AC blower motor sharing the same resistors as the heater motor and I highly doubt that the resistors are built into the switch like the 66 unit, and if the motor has the resistors built in I would expect them to fail open circuit and thus one of the speeds would not work.

Does anyone know how the three speed switch function is supposed to work for an OEM 66 AC underdash unit?

[bryancobb]

Just tested mine in the floor hooked to a battery,  a few weeks ago.  All three switch positions worked as they are suppose to.  I suspect your switch is bad, the wires are hooked up wrong, a wire is broken into, or the motor is bad or incorrect.

[e093116]

I figured it out.  Two wires were reversed on the switch, which was how the thing was connected when it came into my possession.

The resistance is built into the motor and an external resistor is not used like 65 or the heater blower motor.

For posterity, after breaking the motor down I recorded:
2.8 ohms for red wire
2 ohms for yellow wire
1.4 ohms for orange wire

So when connecting to the switch, the red wire goes on the terminal that is only active in switch position one, the yellow wire goes to the terminal that is only active in switch position two, and the orange wire goes to the terminal that is only active in switch position three.  The terminal that is active in all three switch positions is the wire to the thermostatic switch.  The other terminal position on the switch is the power input.

There is nothing inside the switch except for a spring keeping a copper disc pressed against the terminals, when the switch is rotated, the disc rotates making the appropriate connections.

I should have tried harder before posting...but that is what I get for assuming it was wired correctly to start with.  At least everything works.