I'm not sure what year car you are working on, but for my 65 & 66 cars, I have found the various original Ford diagrams that are posted on the averagejoerestoration.com website VERY helpful.    The links to various diagrams are on the right side of the home page.  The heater wiring is on the "accessories" diagram.

My 66 is a 6 cyl car and the 65 is a V8 car.  The differences I have noted between the two seem to be based on the fan speeds offered, not cylinders.  My 65 has a 2 speed heater blower, and the 66 is a 3 speed blower.

Tim C is correct.  The heater blower switches are completely different and not interchangeable.  The 65 uses a two-speed motor while the 66 uses a single speed motor that incorporates a resistor block the changes the 3 speeds.  There is no difference between 6 cyl and V8 applications for each of the those years.

TimC wrote:

I'm not sure what year car you are working on, but for my 65 & 66 cars, I have found the various original Ford diagrams that are posted on the averagejoerestoration.com website VERY helpful.    The links to various diagrams are on the right side of the home page.  The heater wiring is on the "accessories" diagram.

My 66 is a 6 cyl car and the 65 is a V8 car.  The differences I have noted between the two seem to be based on the fan speeds offered, not cylinders.  My 65 has a 2 speed heater blower, and the 66 is a 3 speed blower.

While the switch has 4 positions; off, speed 1, 2 & 3, this is usually referred to as a 3-position switch.

Switch wiring goes to 3 prong on resistor - correct
The single wire (yellow) on the resistor block goes to the firewall bulkhead connector, then to the motor.
Power is supplied from the fuse block (brown wire) to the bulkhead connector, then to the motor.

wsinsle wrote:

rgamble wrote:

im guessing the single prong left on resistor needs 12v switched power (wasnt there)

Thanks in advance for help

You would think that would be the spot for positive but its not. As Bob states the brown wire comes from the fuse block to the fire wall connector and supplies +12 volts to the motor. The yellow wire is the return and goes back to ground via the resister block to the switch. To much paint and or rust behind the dash where the switch mounts will cause loss of ground and the blower motor will not work.
 

Walt ... Maaate!!  Long time no hear .... are you and Brenda gunna make the bash??

rgamble wrote:

So the yellow wire in the harness that runs along the firewall that connects directly to blower motor should go back to harness block, run under dash and then hook to the single wire tab left on the resistor on heater box?

 

That is correct. Hope this pic helps.

Barry I sent you a message.