12 volt lighting 4 camp trailer help

Submitted: Sunday, Feb 24, 2008 at 21:27
ThreadID: 54898 Views:2174 Replies:5 FollowUps:0
This Thread has been Archived
Im in the process of wiring up some lights for my c/t
Im using 20w diocrioc downlight run with 4mm cable, with a rocket switch to turn them off/on .
I:ve mounted the light & gimble in a small ply box with a switch in it to turn off & on,with the 4 mm cable direct to the the battery terminals, with a in line fuse in the positive line. sounds great in theory hey.
Well ! I keep blowin fuses (10 amp 20 amp 30 amp )
my calculation if are correct Amps = watts divide by volts?)
Amps = 20 watts /12 volts=1.666 should be 1.66 amps correct?
Why then am i blowing up 30 amp fuses?
Would love some input from those that are far more intelligent than me .
( which would just about include everyone)
Are my formulas correct ?
Back Expand Un-Read 0 Moderator

Reply By: Gronk - Sunday, Feb 24, 2008 at 21:43

Sunday, Feb 24, 2008 at 21:43
You have a short !!!!

Take out the globes, and if the fuse still blows when the switch is turned on, then you have a short in the wiring !!!!
AnswerID: 289206

Reply By: oldtrack123 - Sunday, Feb 24, 2008 at 21:45

Sunday, Feb 24, 2008 at 21:45
Your formula is corect.,some thing is wrong!,are they definatly 12v bulbs only[not 240v units with transformer ]??
Suggest you take out the bulb &see if you still blow fuse ,if so you have ashort circuit smewhere
AnswerID: 289208

Reply By: Derek from Affordable Batteries & Radiators - Sunday, Feb 24, 2008 at 22:19

Sunday, Feb 24, 2008 at 22:19
Hi Walks

1) Are they 12V globes ?
2) Are they wired in parallel or series ? (Must be parallel)
3) Have you got a fire extinguisher handy ?

I do not recommend this type of globe in a wooden box unless it is quite large and has air flow. I don't know why the fuse is blowing but it may be just your luck that you can't get them working. Use the proper holders for this type of globe or switch to LED or Fluoro.


AnswerID: 289220

Reply By: walks - Sunday, Feb 24, 2008 at 22:29

Sunday, Feb 24, 2008 at 22:29
thx ill check tomorrow
AnswerID: 289225

Reply By: Member - John and Val W (ACT) - Monday, Feb 25, 2008 at 09:07

Monday, Feb 25, 2008 at 09:07
I use these lamps too - they provide excellent pure white light. Not as efficient as Leds or fluorescents, but they more than make up for that in quality of light. As Derek says, provide plenty of ventilation, since a lot of that 20W will be released as heat, and of course use only the bulb and socket - NO transformer. You will need high temperature wire going into the socket, not plastic coated stuff for the first few inches as that will melt and short out. You definitely have a short somewhere in your wiring - maybe in the lamp socket. I wouldn't go above a 10A fuse, and for fault finding I'd temporarily put a 12V lamp in series with the line at the battery to show how much current is flowing and economise on blown fuses.


J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 289261

Sponsored Links