SAE 2 Pin


Basics of SAE 2 Pin Connector Assembly Polarity

by on Feb.04, 2012, under Polarity

Whenever one contemplates use of SAE 2 Pin connectors, an understanding of, and attention to, “polarity” is vital.  Vital in terms of safety, and avoiding possible damage to components.

For the novice (and those who have forgotten) – “polarity” means identifying the “hot” (+) positive side of the connector vs. the negative (-) side.

When there are leads of different insulation colors, say red and black (or white) – the red insulation by standard indicates “hot” (+) positive.

Understand this is a standard, but one should always test to confirm.  Such a test would entail connecting a voltmeter contacting the end of this red insulated lead at the connector and ground.  If there is a voltage indicated (probably 12 volts), then we have confirmed this is indeed the “hot” (+) positive side.

Obviously, with respect to the (-) negative side, the opposite would be the case.  In accordance with standard, this would be indicated by an insulation color other than red – usually black, or white.

Understand that there are times when a color other than red is used to indicate “hot” (+) positive.  For example, if there are several “hot” (+) positive wires (such as in the case of car stereo wiring, i.e., radio power, and keep alive power for memory) a color like yellow might be a “hot” (+) positve wire.

Another application in which there will be multiple “hot” (+) positive wires would be in a trailer light wiring harness and at the vehicle’s disconnect plug.  Even for simple trailer light wiring systems, there may be three “hot” wires – each for various lights (running lights, turn signals, brakes).  Of course there will be a ground (usually black) shared by each of these individual circuits.  In fact, the metal trailer frame is the ground for individual lights in many cases.

While on the subject of trailer lights, it should be noted that this an application in which the SAE 2 Pin connector can be found.  In fact, it is often called a “2 pole flat trailer connector”.  12″ red and white extensions with these connectors can be readily found in the trailer hitch (trailer lights, wiring and connectors) area of your local discount automotive store – most certainly Hopkin’s products.  These are great, certainly filling the bill in many other light applications.  “Light” meaning low current applications, since the wiring is generally 16 or 18 AWG.

These extensions are true “extensions”, i.e., properly connected, you end up with the polarity you started with… at the far end of the extension.  …if the red “hot” (+) positive wire is leading to the female side of the SAE 2 Pin you want to extend 12″… upon coupling the end of one of these 12″ extensions with the red wire leading to the exposed male pin…  the opposite end will have the red wire of the 12″ extension leading to the female side of the SAE 2 Pin at the other end.

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