fan polarity

[terrencecolp]

I own a 1976 Tradewind. The range hood fan has two wires coming off the fan. A red and a black. The black runs to the switch. Which wire is positive and which negative?

[Bruce B]

Typically, 12 volt devices are switched from the positive side.You can always just hook it up and see if it blows in or out and then correct if wrong. My guess is the switch is positive though.
Bruce

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[Rich W]

On 12 volt systems red is positive, black negative. The ground/black wire runs to the switch while positive/red runs to the device. If you wire them backwards the fan will run in the reverse direction.

Rich

[terrencecolp]

Thanks for the help. You know I always heard red positive, but I was rewiring my lights in the trailer, and they were strung with the black wire positive. Go figure, I guess when they ordered the fans from a manufacturer, well you know.

[Bruce B]

I would still try it out before I buried the wires. It is not unusual to find German devices with black positive wires and it is still normal to switch positive rather than the ground side. richw46 may be correct but I have seen lots of examples were the black goes to positive including our 2012 Bambi...
My final 2 cents!
Bruce

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[Rich W]

I used to have a car with a positive ground and yes, it was European. If you think the red wire is ground I'd buy a small multimeter and check it. Multimeters are a good tool to have anyway; check voltage and check continuity.

In the DC world in the US red is positive but there are plenty of people who will use a black wire just because they have that and not a red one. On a fan, if it's wired backwards it will just run backwards, pulling outside air into the AS. Light bulbs don't care but radios can be damaged.

Rich

[J. Morgan]

Regarding the tail lights using different colors than red and black to denote positive and negative, that is different.

Most trailers have adopted GM's color code. Brown and/or black for tail and running lights, yellow for left turn, green for right turn, red for brake lights if a separate brake light circuit is used, and white for ground.

[Protagonist]

Originally Posted by J. Morgan

Most trailers have adopted GM's color code.

I thought it was the SAE J560 standard, not a GM standard.

[J. Morgan]

I suppose it may well be SAE standard, but I am a person who learned from doing and it in the process I found that GM used this standard before Ford did and I am pretty sure before Chrysler.

<shrug>

While this may have been an SAE standard for a long time, it seems all manufacturers didn't apply this standard.