Hey guys, can someone help me figure this out?

On this image of the Fiero's blower motor resistor... can you tell me which of these coils is for higher speed which coil is for the slower speed (0/1/2/3 setting on the switch)?





My general understanding is that a larger coil has lower resistance because it uses thicker wire and fewer turns, while a smaller coil, which often has more turns of thinner wire, can create higher resistance. But I'm also confused because I think MORE coils leads to higher resistance... I got a CompSci, not an EE... can someone easily answer this for me?


Thank you!!!

[This message has been edited by 82-T/A [At Work] (edited 10-21-2025).]

Todd just use an ohm meter and it will show exactly what resistance. sleek

quote Originally posted by sleek fiero: Todd just use an ohm meter and it will show exactly what resistance. sleek

But that requires more work than posting a message on Pennock's? Haha...

... and just to be clear, a higher resistance means less voltage and a slower fan speed, correct?

[This message has been edited by 82-T/A [At Work] (edited 10-21-2025).]

quote and just to be clear, a higher resistance means less voltage and a slower fan speed, correct?

quote Originally posted by Hulk: At high setting, it will put out battery voltage to the fan {doesn't use resistor set}. As you turn it down, it pulse width modulates the 12V to slow the fan down. Think of a strobe light: constant on would be high, then as you turn it down, the light flashes on longer than off. As you turn it down half way, it flashes on and off the same amount. At the lowest, it's off more than on. That's called duty cycle, similar to how the fuel injectors operate. Anyway, that's what this module will do with the 12V to the fan, thereby varying the fan speed with the duty cycle.

[This message has been edited by Vintage-Nut (edited 10-21-2025).]

quote Originally posted by Vintage-Nut: At high setting, it will put out battery voltage to the fan {doesn't use resistor set}. As you turn it down, it pulse width modulates the 12V to slow the fan down. Think of a strobe light: constant on would be high, then as you turn it down, the light flashes on longer than off. As you turn it down half way, it flashes on and off the same amount. At the lowest, it's off more than on. That's called duty cycle, similar to how the fuel injectors operate. Anyway, that's what this module will do with the 12V to the fan, thereby varying the fan speed with the duty cycle.

RGR, that's good to know, I appreciate it... and it makes sense why it doesn't get hot when on full.

Do you happen to know though which coils are used in which instances of speed variation setting?

High - Relay power
Med - One Coil (A to B)
Low - Both Coils (C to B)

quote Originally posted by Vintage-Nut: High - Relay power Med - One Coil (A to B) Low - Both Coils (C to B)

THANK YOU!

From the above post from VN.....

quote

Originally posted by Hulk:
At high setting, it will put out battery voltage to the fan {doesn't use resistor set}. As you turn it down, it pulse width modulates the 12V to slow the fan down. Think of a strobe light: constant on would be high, then as you turn it down, the light flashes on longer than off. As you turn it down half way, it flashes on and off the same amount. At the lowest, it's off more than on. That's called duty cycle, similar to how the fuel injectors operate. Anyway, that's what this module will do with the 12V to the fan, thereby varying the fan speed with the duty cycle.

end quote

This is grossly erroneous.

Resistors operating in series (or parallel) add resistance to the circuit, thereby lowering the voltage to the motor.

Pulse width modulation is NOT a function of fan speed control in a resistance circuit.

[This message has been edited by olejoedad (edited 10-21-2025).]