Heater motor wiring

Fireguyfire

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I’m going through the electrical on my 70 300 convertible; the previous owner had removed the factory wiring and added an aftermarket harness that lead to only half of things working, etc.
I’ve tested and reinstalled the factory wiring harness, and am reconnecting things back up as per the factory.

My question is regarding the heater blower motor that is located on the heater box on the upper inside of the passenger side fender near the power antenna.
There are 2 wires that come from the blower motor; 1 black and 1 red. The black goes through the firewall grommet and grounds to the inner firewall; the red goes through the firewall grommet and was cut and hanging by the passengers feet.
I’m assuming this red wire from the blower motor must go to the blower motor switch? All of the connectors are used on the heater blower switch connections, so I’m guessing it should tie into the factory harness somewhere behind the glove box? I don’t see any cut wires in the factory harness.

The shop manual wiring diagrams aren’t helping me, so I thought I’d ask here and see if o e of you C body gurus can help me out with where the red blower motor wire should go.
 

Big_John

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I can't remember exactly where it connects. Got that CRS disease, don't you know.

It should go to the connection on the heater box where the resistors for the heater motor are located.
 

Big_John

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Turn to page 24-35 in your FSM (if your car has AC) and 24-2 (if it doesn't)

24-2 shows the motor lead plugging into the resistor block.

24-35 I'm going to walk out to the garage in a bit and I'll confirm that on my A/C equipped 300.

EDIT: The A/C version plugs the positive wire into another plug off the wiring harness on the firewall. In the FSM, that follows down and goes through the same molded gromet that the A/C compressor feed does.
 
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CBODY67

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One thing to understand . . . the instrument panel switch only changes CIRCUITS and does not control the fan speed directly. What it does is change the circuits which go to the motor, via the blowr motor resistor mentioned. There are three large to small-gauge wire "resistors" in the resistor "block" which is cooled by the air going into the hvac case.

The lower-speed "wire resistor coil" will be larger diameter than the higher speed coils, so you can visually determine which coil is which. End result is that more wires "to" the block with only one wire going to the motor, power wire that is. As the motor usually has some rubber grommets which insulate it from the car body (noise/vibration isolation), the motor will need to be gounded by a separate wire, however that might happen, which the FSM wiring schematic could detail, or the related illustartions noted.

Just some thoughts,
CBODY67
 

Fireguyfire

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The spade connector that the motor feed goes to was hidden by the angled 2 spade connector below it.
 
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