Driver fan in bus with no A/C! Need help quickly

[silvermachine]

Hey all, quick question here. I’m trying to install a simple 12v driver fan to my bus. I unhook the panel where you control the heater, accessories and whatnot and am confronted with two terminal blocks and I’m not sure what’s what.

The fan originally had a two-wire cigarette lighter charge port, but I snipped that connector off, as I won’t be needing it. Instead I’ll be soldering ring terminals directly to the wire. One of the fan wires is black and one is black and has a white stripe down the side. I’m assuming that’s the positive wire.

The only issue is that I’m not sure how to hook it up to the ports to get power to the correct wires. I’ve attached a few photos I’m hoping will help.

Basically I just need a basic breakdown of what’s positive and negative in this type of terminal port and where to hook things up to get power to my fan. It’s getting way too hot to put this project off any longer. Thanks for helping out!

1st photo: general view of switchboard
2nd photo: R side of terminal block
3rd photo: L side of terminal block
(They are two separate blocks which appear to be connected)

[CHEESE_WAGON]

In most 12V circuits, the 12V+ will be the lighter color of the two, the ground the darker. Where wire colors are same color, but one has a stripe, the striped wire will usually be the 12V+. You can also use a test light to determine which terminals are 12V+. Ground wires will also be traceable to a termination of some sort on the bus body or chassis.

Might also consider a Vintage Air A/C unit.

[Native]

If you did not throw away the 12-volt cigarette lighter plug, then you can use that to determine which wire is positive and which is negative. The wire connected to the outside of the plug will be the negative and the one connected to the center will be the positive.

[CHEESE_WAGON]

The nice thing about such devices as electric motors and light bulbs is that reverse polarity on DC voltage does not generally hurt them, a light bulb will burn either way or depending on how it's grounded, could blow the bulb. An electric motor will generally just run reverse of its intended direction with the polarity reversed. Reverse polarity is far more of a problem with electronics than light bulbs and motors.

[Native]

That is so true.

[silvermachine]

I’m really wondering more about the terminal blocks themselves. I’ve never worked with one before. Gonna use a multimeter and try to figure out what row is pos and which is neg. It’s just little intimidating at first opening up a panel like that. Dusty as hell in there. Gonna try to clean up the terminals a bit with some electronic cleaner. Thanks all.

[Jolly Roger bus 223]

for power you could figure out which side of the switches is incoming power and just piggy back your new switch off of one of those
the switches normally just break the power going into and out of the switch.
and the switches or accessory the switch serves should already protected on a fuse somewhere
a ground is just a ground and on the back wall of your panel you have 2 or 3 wires screwed to the back of the panel so that is definitely a grounding point for a few of your things.
good luck

[CHEESE_WAGON]

I would highly recommend a dedicated switch and/or relay. Too much load on those switches can overheat them and possibly cause a fire.

[Jolly Roger bus 223]

i was saying piggy back off of the incoming power wire to add another switch for the fan not the out going power side.
it would drive me crazy to have to turn my overhead lights on to make my fan run.
but just as simple to figure out which side of the terminal strip is hot and connect to it. and add an inline fuse before the new switch

[Jolly Roger bus 223]

of course he would have to pick the switch that has a fuse big enough or small enough (sized properly) to protect his fan.
but he is going to need to know which size fuse that would be either way to just piggyback or to run from the terminal block.
i would think a 5-amp to run a little fan but we dont know what the OP has.

[Ranchorossa]

Don't go by wire color. White is usually common and black is hot. A multimeter will take less than 30 seconds to tell you what wire is hot. In a worst case scenario, run two wires directly to the batteries, adding a fuse of course, and your good to go.