View Full Version : Solved Motor wires?

01-31-2012, 11:23 PM
I am new to electrical engineering so I don't know a lot of stuff about electric parts. I have an electric motor and it has a red, black, and yellow wires. I'm pretty sure red and black are for power (+,-) but what is the yellow wire for?

PJ Allen
01-31-2012, 11:26 PM
It might be a "tachometer". It may provide pulses which correlate to revs.

02-01-2012, 12:44 AM
Black, red, yellow is a common color combination for motors that use a starter capacitor. Could also be a multispeed synchronous motor. Or...

Who knows, but without some specs or at least a photo there's no telling what kind of juice the motor expects. There are dozens of types, in all kinds of shapes and sizes.

-- Gordon

02-01-2012, 06:10 AM

In my opinion, I would imagine that PJ Allen is correct.

It might be a "tachometer".

Personal computer fans are a classic black, red, and yellow wire combination. In this instance, the yellow wire is definitely for measuring the RPMs of the fan. So do some reading on computer fans which should result in more knowledge.


Duane Degn
02-01-2012, 06:22 AM
While we're guessing, why not a brushless motor? They have three wires.

02-01-2012, 06:33 AM
Okay, I now see the light. :) Okay, besides being a brushless motor or having a third wire for monitoring RPM, what are the other possibilities?


02-01-2012, 08:45 AM
Well, for rc servos, PWM signal/control?

02-01-2012, 02:07 PM
The yellow wire is always for the airbag...

02-01-2012, 03:09 PM
Here are pictures 891878918889189

Phil Pilgrim (PhiPi)
02-01-2012, 03:18 PM
It could be a permanent split-capacitor motor, requiring an external cap to run: http://www.allaboutcircuits.com/vol_2/chpt_13/9.html. The cap provides a phase shift for directional control, and the motor can be reversed by switching leads that the cap is connected to.

It might also be a two-speed motor, commonly used for fans


02-01-2012, 05:42 PM
Being a 120V AC motor, well that puts a different SPIN on things. Disregard my previous posts :)

02-01-2012, 06:04 PM
No wonder. Hehheh embarassing (SOLVED)

02-01-2012, 06:18 PM
As I suspected, and Phil surmised, an AC motor using an external cap or multispeed taps. I'm betting on the former, given that the motor has an integrated cooling fan and a pulley that appears to have quite a bit of torque wear on it. I'm guessing it's for the evaporator fan on a refrigeration or air conditioning unit -- but that's just a guess. You can determine some things by using a meter on the wires, but peeking inside is best, assuming you can't find it by the model number.

-- Gordon