Heater Fan Switch Wiring Help

[F16Waldo]

Replacing old heater fan switch in 83 Pininfarina Spider and need wiring clarification/guidance (looked but could not find a previous thread). Just purchased car last spring so little knowledge of previous work or changes that may impact starting parameters.

Switch is located on lower center console and is 3 prong, with 3 distinct wires connecting to the prongs...solid red, yellow with black stripes, blue with black stripes. (wish I could figure out how to attach pics!)

Current switch: On the bottom it has two male prongs offset to one side, and a single male prong offset on the other side. On the two prong side, there is a RED dot over the outer prong. On the single prong side, there is a GREEN dot over the prong.
Current wiring has on the two prong side a blue/black wire on the outer prong (which has a RED dot on the switch) and yellow/black wire on prong next to that (middle prong). Then on other side, the red wire is attached to the prong with the GREEN dot.

New switch (from AR): On bottom it has 3 evenly spaced male prongs and a single GREEN dot over one of the outer prongs.

Q: What is correct wiring scheme for new switch? Find it confusing that currently the red wire is connected to the prong with the GREEN dot rather than the prong with the RED dot.

Appreciate any help/guidance. Also doing this in conjunction with installing new carpets (I have the thing torn apart anyways) so any advise/words of wisdom in that realm greatly appreciated as well!

Cheers
Waldo

[zachmac]

I believe you'll find the yellow/blk is the feed in, the power supple wire. Attach it to the center prong. The switch simply toggles left or right to connect the center to the outer prongs.

The Red is the low speed fan wiring, and the Blue/blk is the high speed. It really doesn't matter which you put on which outer prong unless you have a strong preference for which way the switch is toggled when you are on low or high speed. I don't recall if your switch is mounted in the console left to right or fore and aft. If it is like my car, side to side, I connect the red to the prong closest to the driver as switch toward driver as low and toward passenger as high makes sense to me. If fore and aft I'd connect red to rearmost and blue/blk to front most.

BTW, you can't hurt anything if you get it wrong so it's okay to just try the three wires connected however you like until it works. If you get the hot lead on the wrong post it will just only work on one speed. Again, yellow/blk should be the input wire and goes on the center.

[zachmac]

BTW, not that you asked and what I said in my first post will suffice but if you want a full understanding of the circuit here goes:

The heater blower motor is a simple single winding motor. The two speeds are achieved by either applying a reduced voltage across the winding to ground by routing power to it through a resistor (low speed) or by passing full voltage directly to the windings with no resistance (high speed). So the fan has three wires, a red input that passes power through a resistor (low speed), a blue/blk wire that passes full voltage (high speed) and a black ground wire (attached most usually to the front left mounting bolt for the heater housing to ground to chassis).

The power to the red or blue/blk wires is toggled via a console mounted three position switch, off (centered) and low / high (switch toggled to one side or the other). Power into the switch is via the central terminal and is fed from fuse #2. Fuse #2 is in turn fed from the ignition switch INT post that should only be powered when the ignition is ON.

So, if you make your connections with the key off you are safe. If you make your connection with the heater fan switch in its center position you are safe. If you make your connections with the key on and the switch toggled one way or another off center the worst case result is the fan will operate in low or high speed. There is no path through the switch that doesn't pass the power through the windings so you are in no danger of grounding a hot lead.

[F16Waldo]

Thanks Zachman! Great info and nice to know the potential to harm the overall system is negligible if I goof it up.
Cheers
Waldo