UK Help! Wiring a 12v camper van roof fan

jimwood · Apr 9, 2020

Hello, as an amateur camper converter with limited electrical experience, I was wondering if some kind soul could help please?

I bought and fitted a 12v Maxxair Deluxe roof fan, which I temporarily fitted unfused and straight on to the leisure battery - it worked fine.

However, I then attempted to fuse the circuit with a 12v blade fuse box/holder which didn't end well.

I extended the wires from the fan with the same gauge wire, brought them back to the fuse box, connected the box to the leisure battery again using the same gauge wire (will upgrade this wire when I add more devices), and fitted a 10 amp fuse. I can't remember the exact order in which I did those which is probably important, but at some point the fuse blew, and the fan refused to work ever again, with neither a new fuse nor connected directly to the battery.

I've been very lucky to get a replacement fan sent out, but I can't afford to break this one! Can anyone suggest where I went wrong please? I've attached a picture of the fuse box below, minus
the fuse.

Any help would be massively appreciated. Thank you!

Jim

buzzlightyear · Apr 9, 2020

stick on here the wiring diagram of the item and wiring diagram on what you are doing .

jimwood · Apr 9, 2020

Thank you Buzz. There's not much to it really...

buzzlightyear · Apr 9, 2020

View: https://youtu.be/oOQHe_cZtI4?t=34

Mike Johnson · Apr 9, 2020

The bottom connection to your fuse holder has a blue connector on it, are you sure that's the + because thats how its connected in to the fuse holder? have you a multimeter to check the polarity?

JBW175 · Apr 9, 2020

Out of interest, what bus you got?

buzzlightyear · Apr 9, 2020

JBW175 said:
Out of interest, what bus you got

a conked out one .lol.

pc1966 · Apr 9, 2020

If it blew the moment you connected it up I would suspect revered polarity (i.e. you got + & - swapped somehow).

If it blew at some random time after you had wired the fuse, etc, in then it might just be a random fault. But I would check very carefully the polarity!

JBW175 · Apr 9, 2020

buzzlightyear said:
a conked out one .lol.

I know that pain only too well...??

Lucien Nunes · Apr 9, 2020

Agreed, the only way damage is likely to occur to the fan is through reverse polarity, which will often kill a device instantly and blow the fuse too, as many things look like a short-circuit in reverse, and even more so once they are fried. Having both leads to the fuse box black is a trip hazard for reverse polarity.

As an unrelated aside, I am wondering why there is insulating tape wrapped around the leads feeding the fuse box. What is it hiding? Is there something dodgy about the crimp terminals? Also, when making permanent connections, the outgoing leads should be fitted with ring terminals (I realise the present leads are probably temporary)

jimwood · Apr 11, 2020

Thanks everyone, it's all working perfectly now. I haven't changed the circuit, I just approached it with a bit more confidence knowing that it was probably just a temporary polarity mixup last time.

@Mike Johnson thanks for the advice, that blue connector is just the only colour i had spare the time
@JBW175 It's a 95 vw t4 mate, 2.4d, LWB. i love the thing
@pc1966 and @Lucien Nunes thanks for the heads up about polarity

Lucien, the insulating tape is just me being over secure in addition to crimping, and I had no heatshrink at the time. Ring terminals fitted now too

Thanks again, very much appreciated!

Lucien Nunes · Apr 11, 2020

the insulating tape is just me being over secure in addition to crimping, and I had no heatshrink at the time.

A crimp terminal should make a secure, completely insulated connection, strong enough that if you put the ring in a vice and give the cable a hefty pull, the cable should rip apart into stretched and broken strands without pulling out from the crimp as such. Up to that point, no copper should be visible, so no further insulation is required. If you are not achieving this, your terminals / tool / method are mismatched or faulty.

The bottom connection to your fuse holder has a blue connector on it, are you sure that's the +

that blue connector is just the only colour i had spare the time

?!?! The colour of the terminal indicates the size of cables it fits and the correct tool die to use. Blue is normally 1.5-2.5mm². Using the wrong size terminal for the cable will likely cause a bad connection.

pc1966 · Apr 11, 2020

You really should have a ratchet tool for the crimp terminals as the hand pliers type are pretty useless. While they vary in quality and price, you can get ones that are good enough for most folk for around £12: