Extra wires under passenger side of dash and blower motor wiring

[mx71]

I've got a bunch of plastic and male/female little pin connectors under the dash not connected to anything. There's a female spade plastic connector coming off the fuel pump relay, a female and male pin to the right of the blower motor, female and male pin to the left of the blower motor, and a bunch of plastic connectors more toward the center of the dash. Does any one have a picture of what these do? I found them when confirming if my choke was working or not. I don't have A/C, and currently my blower motor blue wire is wired into the relay above it, and the red wire is just going to a power I found, and does operate correctly with the switch. (which is another weird one, as the switch only operates on three speeds, but the plastic trim indicates 4 speeds).

[Crashtd420]

Ah you gotta luv it.... some could be just for extra accessories or features your truck doesn't have....

As far as the extra fan speed which one doesn't work?....

I'm not really familiar with the 720 wiring but usually with a blower motor the first few are through a resistor for the lower speeds then full power for the highest speed....

On my chevy I had only the first 3 settings .... fan fell out of housing and overloaded and fried the high speed relay....

That last pic.. the connector with all the blue wires is the resistor unit....

[mx71]

Well, it's not that a certain fan speed doesn't work, it's that the selector only has three options and the plastic trim piece says it should have 4. Maybe someone switched the trim piece or selector at some point?

[Crashtd420]

Well, it's not that a certain fan speed doesn't work, it's that the selector only has three options and the plastic trim piece says it should have 4. Maybe someone switched the trim piece or selector at some point?

Ahh.... I would have to agree something was changed then....

[mx71]

I figured them out! The two little dangly pins on the right of the third picture (blue and red) are the proper connections for the blower motor, and pretty much all the others are a/c or diesel related, which I have neither. The best I could find for the one in the second and back of the third picture by the fuel and choke relay is that it just isn't used for anything.

[Lockleaf]

Yes you are correct most of that is ac. About 90 percent of the ac wiring is built in to every harness by that year. Only a couple bits of wiring between components are missing to wire in ac.

 

Older 720s only had 3 speed fan switch. Later years had 4 speed. Old truck, someone just used what was around.

[datzenmike]

 

See where all the blue wires go? Remove those two Philips head screws and lift that unit out. Behind, will be several that little coils of wire. The speed switch selects them in various combinations to slow the fan speed. The highest speed has no coil at all. The slowest the most. Look for a coil that is open and not connected.

 

Or count them. Two coils is a 3 speed and three coils is a 4 speed.

 

The fourth speed was added Jan of '84

.

[mx71]

Well then it should have a 4th speed, but the selector isn't allowing it.

[datzenmike]

Power supplies the fan and the ground is switched through various resistances to get the speeds. If forth is the highest speed, it's just a straight connection to ground.