Obvious to many, I’m sure.

[CamperJack]

I have always thought red was positive and black was negative. But I’m half way through installing my Fiamma turbo vent and it has blue and brown wires!

Which is which please?

Thanks in advance!

By the way the hole cutting in the van roof was remarkably easy and it all fits!!

 

[Lenny HB]

We have a Fiamma Turbo fan that clips in our big rooflight connect the power one way and it blows in reverse the polarity and it extracts.

Lenny's Modding the new Gin Palace

Lenny fridge mods, a favour where did you tap into the fridge circuit for the controller and fans.

www.motorhomefun.co.uk

 

[CamperJack]

As suggested by Jimbohorlicks get a cheap multimeter from somewhere like Toolstation or Screwfix. It will cost around £10 and you can't safely work on your MH without one.

I have one and use it. However, given that it is just two wires hanging out of a fan that’s just come out of a box and isn’t connected to anything how will a multimeter help determine which wire is which?

Just to be clear this is a genuine question from someone who’s unsure about these things, not a sarcastic comment from someone trying to be clever.

 

[CamperJack]

I think maybe the OP was trying to identify the wires coming from the fan rather than those sticking out of the ceiling.

Exactly! The wires in the ceiling were put there by me! Black is negative and red is positive!! Easy!

 

[Mrsambulancekidd]

Get a bulb style tester, better than getting confused and going fizz bang.

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[CamperJack]

I think there has been a little confusion, for which I sincerely apologise.

The wires I was unsure about were the ones coming out of the fan, and not connected to power. Therefore a multimeter would be no good to determine if the wires were negative or positive. (I think.)

The wires from the battery, coming out of the ceiling were put there by me. Black is negative and red is positive. Easy.

I’ve wired it up and it works!! Hurray.

Very happy because this is thee first thing I’ve wired up in the van! Feels like a huge step forward!

 

[Two on Tour]

I think you could do with practising your silicone finishing skills though.

You might find these and a wet finger a useful addition for finishing off silicone sealant.

Amazon product ASIN B009L9PJYS

 

[CamperJack]

I think you could do with practising your silicone finishing skills though.

You might find these and a wet finger a useful addition for finishing off silicone sealant.

Amazon product ASIN B009L9PJYS

Yes, I’m far from neat. But I’ll be amazed if water gets through it. That’s the main thing. And only I’ll see it on the roof when cleaning the solar panels.

 

[autorouter]

The wires from the battery, coming out of the ceiling were put there by me. Black is negative and red is positive. Easy.

I’ve wired it up and it works!! Hurray.

So, after all that, which was the positive on the fan - blue or brown?

 

[DBK]

I have one and use it. However, given that it is just two wires hanging out of a fan that’s just come out of a box and isn’t connected to anything how will a multimeter help determine which wire is which?

Just to be clear this is a genuine question from someone who’s unsure about these things, not a sarcastic comment from someone trying to be clever.

Sorry, I misunderstood but I'm very easily confused.

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[CamperJack]

So, after all that, which was the positive on the fan - blue or brown?

I went with the majority on here and wired it up as blue being positive and brown being negative. I also put red tape on the blue cable and black on the brown, so I don’t sit there scratching my head if I ever see the wires again.

I’ve no idea if that’s correct.

Flick the switch one way and it sucks air in, put it in the middle to turn it off, flick it the other way and it extracts air out the van.

As the switch isn’t labeld I’ve no way of knowing if it’s right.

It’s got a 5A fuse in and I had it on for about half an hour and it never poped the fuse or caught fire so must be okay or I’m running it backwards but it doesn’t matter?!

 

[CamperJack]

It doesn’t half blow though!

I wonder if it would be possible to put in a switch, like a dimmer switch or something, to enable the speed to be altered.

 

[Shaders]

Usualy brown positive an blue negative

 

[peterc10]

Usualy brown positive an blue negative

Not on 12v

 

[autorouter]

I have a Hymer (German). The water pump failed in France, so I bought a replacement pump (Italian). The pump wire was 2-core, brown +, blue -. I had to wire brown to blue and blue to brown. For vehicle 12V, there's NO Europe-wide standard, you always need to check.

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[TinaLes]

Glad you got it working, all is good now, you know Blue Is positive, Brown Negative.
I never take any 12V wiring colours for granted, as our van has every colour going on, orange, yellow, green, black & blue. Especially when trying to find the D+ or the S+ feeds.
But I agree checking polarity on an accessory is not easy before its connected as there is no power coming from it.
That's the first time I have seen a roof light held in with Royal Icing,be better when you have put the Pink ribbon round it I guess.
Famous last words come to mind here...... Blimmy if that leaks now, I will eat my? what was it?...hat,shoe?
Well done, now put your feet, and enjoy the breeze.
LES

 

[Geo]

This post really does confirm why women live longer than men

 

[TheBig1]

a little knowledge can be a good thing, but some times it is a menace. My uncle popped into my workshop one day and asked if he could have some 10a automotive cable. I asked him if he needed a particular colour? No was the answer, so I handed him a part used spool of yellow.

A few weeks later he asked for help on a car he was fixing. It had suffered a fire under the dash and he had rewired it. But every wire he had replaced was yellow. Now that was a job and a half to sort out

 

[CamperJack]

What’s the correct way to find out then, TheBig1?

 

[Rosemary1]

Yes, I’m far from neat. But I’ll be amazed if water gets through it. That’s the main thing. And only I’ll see it on the roof when cleaning the solar panels.

You’ll get insects skiing in winter on that

Well done on the fan - I’m rubbish at stuff like that

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[TheBig1]

What’s the correct way to find out then, TheBig1?

There are multiple ways to learn now. When I did, it was at technical college, but there are books, websites and youtube videos now. The basics though are better taught face to face with somebody qualified, who can answer questions and explain directly why what somebody might be attempting is wrong

The vast majority of vehicles are now wired negative earth, as in the battery negative is attached to the bodywork. It was not always the same though. When learning to wire up a van for habitation you need to understand the principle and why it is far better to wire all earths back to a central point rather than just rely on a self tapping screw in the metalwork.

Unlike mains voltage and industrial wiring, vehicle 12v wiring does not have a set colour code. However if all wires at the fuse board are the same colour it can confuse which wire powers which function. So a sleeve or tab on the tail, stating what it powers that connects to the fuse will help with any future diagnostics.

Knowing that "some" converters use blue as positive and brown as negative is useful only when working on those vans. Never take anything for granted, use a multimeter to confirm polarity. Set the meter to 20v DC range and put the black probe on one wire and the red on the other. If it shows the voltage correctly, you have the right polarity. If it shows the same voltage but with a minus symbol, it is the opposite polarity.

In the past a member of fun ran a workshop meet, where people who were interested were shown the basics of using a meter and making proper electrical connections. Maybe we could re-run this again at some point when things return to normal

 

[CamperJack]

a sleeve or tab on the tail, stating what it powers that connects to the fuse will help with any future diagnostics.

I'm using a Blue Sea fuse / negative bus board which has a cover where you can label each wire coming in. I've done that.

Never take anything for granted, use a multimeter to confirm polarity.

A lot of people have said "use a multimeter", which I did when installing new 12V sockets into the cab, using existing wires to a blank and a wobbly old socket. However (as far as I am aware) a multimeter cannot be used for the application I originally asked about - which were two wires coming out of a brand new fan, straight out of the box and not yet wired into anything. Would there be a way to test that?

In the past a member of fun ran a workshop meet, where people who were interested were shown the basics of using a meter and making proper electrical connections. Maybe we could re-run this again at some point when things return to normal.

That's a great thing to do and something I'd be very interested in attending.

 

[Jimbohorlicks]

It doesn’t half blow though!

I wonder if it would be possible to put in a switch, like a dimmer switch or something, to enable the speed to be altered.

If you do that you will need to know which wire is +ve or - ve.

 

[CamperJack]

If you do that you will need to know which wire is +ve or - ve.

I've been looking it up and general opinion was don't do it. They fear burning out the switch. I mean the fan is only 2A, but I'm not confident with mods and I'd probably void the warranty, which states quite clearly not to mod it.

 

[tonyidle]

Not on 12v

Not on anything

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[TheBig1]

The fan you installed is just a simple DC electric motor and can be run in either polarity. The way to tell is see if the motor is marked or power it up and check that it turns in the correct direction, either extract or pulling air in. All a meter would show you is the impedance of the winding in the motor, which to your install would be irrelevant. A simple variable resistor circuit could be used to control the fan speed by reducing the voltage supplied to the fan

 

[CamperJack]

The fan you installed is just a simple DC electric motor and can be run in either polarity. The way to tell is see if the motor is marked or power it up and check that it turns in the correct direction, either extract or pulling air in. All a meter would show you is the impedance of the winding in the motor, which to your install would be irrelevant. A simple variable resistor circuit could be used to control the fan speed by reducing the voltage supplied to the fan

It might be something for me to look into. While I'm impressed by the amount of air it is able to move, with such low amounts of power and how cooling that would be after a long hike in the mountains or extracting steam when I fit the other above the kitchen etc, it would be too cold after a while or too noisy running at full blast over night.

 

[Ian Bosman]

https://householdquotes.co.uk/british-wiring-colours/

• Blue

This is the neutral wire

• Brown

This is the live wire

• Green & Yellow

This is the earth wire

DC supply is supposed to be black, negative, red positive. You usually have the black to chassis with DC so there is no earth as such. Blue & Brown & Green/Yellow is supposed to be for AC supply eg mains electric. Brown is Live, Blue is neutral and Green/Yellow is the earth line connected to the earth supply off the mains in a campsite. So be careful what you are dealing with AC/DC. I carry a plug in thingy which indicates if the three mains wires are correctly powering the van, all three lights are OK, one not it tells you what is wrong, usually live/neutral switched over which in British practice is not good whereas European practice they switch both live and neutral so has no effect on the van mains. Any electrical work you are well advised to get a decent digital multimeter (avoid analogue as they are much more difficult to read and less accurate) which does allow you verify whether AC or DC - the latter being 12 to 14 volts in a motorhome. If all of this bamboozles you then get a professional onto it as getting the wiring wrong can be disastrous and downright dangerous.

 

[SuperMike]

On my American RV they use black and white. I’ll let you guess which is which.

 

[The Old Man]

On my American RV they use black and white. I’ll let you guess which is which.

Only one matters though.

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[Hania]

Going back to my (long-ago) school days - physics, when we were being taught how to wire up a plug : brown is hot, blue is not, green and yellow link the lot !