Electric Fan install wiring question

mudcrewsr

mudcrewsr

Member
Joined
Sep 18, 2012
Location
Wilmington NC
I'm attempting to install my electric fan today but I'm stuck. I've never installed electronics with a relay before and I'm getting confused on what to ground or what to return back to the negative post on the battery.

This diagram is what I was going to attempt. wiring

zhtWxg


My question is first of all is this a correct diagram?

Second question is if this diagram is correct what do I run the neg. post from the fan to? Most stuff I have seen online says ground. Does that mean ground it to the body or frame or does it mean run the negative to negative post on the battery?

The relay is tripping me up in the past I would have just made a loop from switch to fan to battery but I want to do this right and not burn myself to the ground.

Any suggestions or guidance is appreciated.

Thanks all!

-Randy
 
the diagram looks fine to me.

Just ground the fan motor to the chassis

Are you using a thermostat too?
 
The diagram is close.

In short:

Run 12v (+) from battery to fuse to supply side of switch.

Then from load side of switch to relay.

If the switch has illumination, run ground (-) from earth or ground terminal on switch to common chassis/body ground. Doesn't matter Where, just make sure has good path to ground.

Then run larger diameter and larger fuse from battery (+) to relay.

Then from relay to fan 12v(+)

Ground the fan (-) either to frame body or battery. Whatever is convenient and has good path to ground.

Then ground the relay (-).

Put your fuses as close to the battery, as practical and don't over fuse the corresponding size wire.

If anything under fuse the wire size.

Check out this link for wire length vs amperage capacity vs wire size chart.

I don't agree with entire chart but for the most part is correct.

Wire Gauge Amps Ratings for 12 volt Automotive Systems

Again use the correct wire size for the load , and don't over fuse the wire size.
 
Mac5005 said:
The diagram is close.

In short:

Run 12v (+) from battery to fuse to supply side of switch.

Then from load side of switch to relay.

If the switch has illumination, run ground (-) from earth or ground terminal on switch to common chassis/body ground. Doesn't matter Where, just make sure has good path to ground.

Then run larger diameter and larger fuse from battery (+) to relay.

Then from relay to fan 12v(+)

Ground the fan (-) either to frame body or battery. Whatever is convenient and has good path to ground.

Then ground the relay (-).

Put your fuses as close to the battery, as practical and don't over fuse the corresponding size wire.

If anything under fuse the wire size.

Check out this link for wire length vs amperage capacity vs wire size chart.

I don't agree with entire chart but for the most part is correct.

Wire Gauge Amps Ratings for 12 volt Automotive Systems

Again use the correct wire size for the load , and don't over fuse the wire size.
Click to expand...


Thanks Mac5005... I checked out the link. Can you tell me what the color codes mean on that chart? I didn't see an index or anything as to what was good, preferred or bad.

Thanks again!
 
I wouldn't worry about what the color means, for you application it's all in the same color. If you just want to know, then......I have no clue!!:flipoff2: Lol!! Either way 18awg will be fine and your fan "should" say how may amps it will pull. Like Mac said how ever many amps the fan is going to pull, fuse it for less!
 
Btw, based on your diagram you just made your switch a light bulb!!!! You only need to switch a negative or a positive not both. Personally I would switch the negative so run your positive to the coil of the relay then take your negative and run it from (-) through the switch to the (-) side of the coil.
 
krehel24 said:
Btw, based on your diagram you just made your switch a light bulb!!!! You only need to switch a negative or a positive not both. Personally I would switch the negative so run your positive to the coil of the relay then take your negative and run it from (-) through the switch to the (-) side of the coil.
Click to expand...

Thanks Krehel24... trust me I suck at electronics. It's something I am trying to learn but it is black magic to me at this point. can you show me a diagram of what you are saying? I don't understand what you are saying (visually) about I only need to switch a negative or a positive... Are you saying run the positive from the battery (coil) to the relay and then run the negative from the relay to the switch (positive side) to the negative of the battery?

thank you
 
First don't think of a simple switch of having a negative or a positive side it is just a switch. Your relay is made of a coil (needs a + and a -) then a set of contacts (basically a switch) you need to energize the coil so it will close the contacts. If you put a + and a - straight on the coil it will energize (or turn on) so you need to break the flow either break (with a switch) the - or break the + it really doesn't matter witch one you break.
 
krehel24 said:
First don't think of a simple switch of having a negative or a positive side it is just a switch. Your relay is made of a coil (needs a + and a -) then a set of contacts (basically a switch) you need to energize the coil so it will close the contacts. If you put a + and a - straight on the coil it will energize (or turn on) so you need to break the flow either break (with a switch) the - or break the + it really doesn't matter witch one you break.
Click to expand...

Understood thank you. The switch is just breaking the connection/current so wire it through either a positive or negative run. not positive to negative
 
krehel24 said:
I wouldn't worry about what the color means, for you application it's all in the same color. If you just want to know, then......I have no clue!!:flipoff2: Lol!! Either way 18awg will be fine and your fan "should" say how may amps it will pull. Like Mac said how ever many amps the fan is going to pull, fuse it for less!
Click to expand...

Not exactly. If the fan is rated for 40 amps, wire it for 50 amps and fuse it for 45 amps.

mudcrewsr said:
Thanks Mac5005... I checked out the link. Can you tell me what the color codes mean on that chart? I didn't see an index or anything as to what was good, preferred or bad.

Thanks again!
Click to expand...


The color codes in the chart are just showing the different size wire with different colors.

For example.

50 amps at 10' length (battery to fan back to battery) use 10 gauge wire according to the chart. However this doesn't account for heat soak of the wiring in the engine compartment. If it were mine, I would use 8ga for the fan wiring, and fuse it just above rated draw.

The wiring for the coil side of the relay should carry relatively low load.

At roughly 20' of wiring fuse it at 7 amps with 18ga wire or 10 amps with 16 ga wire.

Make sure to use grommets when passing wire through sheetmetal to protect the insulation on the wire.

Whenever possible solder your terminals and wire connections to keep the resistance low, and use heat shrink tubing to seal them.

Switching either the positive or negative of the coil side of relay is fine.

I have a larger diameter fused wire ran from battery to under my dash to an additional fuse block. I use these to power my switches and accessories and then run the wire from switch to relay for each device.

If you run an illuminated switch you will need to switch the positive side.

On my electric fan, I had wired an additional indicator light separate from the switch illumination.

This let me know when switch was engaged and when relay is sending power to fan. If the relay fails, or the fuse blows one the fan side of relay, then you only have the switch illuminated.

This gives you positive feedback in the drivers seat that the fan is receiving 12v.
 
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Mac5005 said:
I have a larger diameter fused wire ran from battery to under my dash to an additional fuse block. I use these to power my switches and accessories and then run the wire from switch to relay for each device.

If you run an illuminated switch you will need to switch the positive side.

On my electric fan, I had wired an additional indicator light separate from the switch illumination.

This let me know when switch was engaged and when relay is sending power to fan. If the relay fails, or the fuse blows one the fan side of relay, then you only have the switch illuminated.

This gives you positive feedback in the drivers seat that the fan is receiving 12v.
Click to expand...

He just went full nerd on you right here!!!!he may start in with ohms law next!! Lol!!! But this IS the best way to do it. If you do it this way it will make it very easy to add things in the future. ...good luck!
 
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