Spotlight Blowing Cigarette / Heater Blower Fuse

Hi there,

I spent this weekend replacing the 4 old halogen roof bar lights on my 2003 110 DCPU with 2x 63w LED spotlights (Amazon product) mounted to the bumper, but have fallen at the last hurdle - every time I hit the ON switch I blow a fuse.

I've reused some of the existing components to wire the new lights and each operates on its own wiring loom with independent 12v 40A relay and switch:

• Power is drawn from the ignition switch, with a 25amp inline fuse
• A 0.75mm2 14amp rated dual core cable connects to the spotlight when the circuit 'opens'
• The ON switchhas been soldered to the cigarette lighter power wire, with 20amp fuse in fuse box

(crude diagram below).


It's the 20amp cigarette lighter fuse (Fuse 16 in the main fuse box) which blows every time I hit ON. I've tried to operate each spotlight in isolation (with the relay power source disabled) but it still blows.

The system operated fine, and the bits replaced were the lights and the wiring running from the relay to the spots. I (foolishly) didn't take a picture of the set up for the relay before replacing the inputs but wired based on diagrams available online.

I'm assuming the blow fuse is being caused by short to ground in the circuit somewhere, but I didn't see any chaffed / exposed wiring from an inspection and would that be the case if both independent switch systems are blowing the fuse? Is the wire insufficient for the current - it has a 14amp rating and by my calculation each spotlight should only be drawing c. 5amps. Could the relay be wired wrong?

Any ideas / thoughts most welcome!

J

Have you wired the relays correctly

Hi, you have an earth shown on your positive switch:

Is it a switch with an indicator light? If not, I would suggest it is there your problem lays.

My Old Landy said:

Hi, you have an earth shown on your positive switch:
View attachment 184912
Is it a switch with an indicator light? If not, I would suggest it is there your problem lays.

Click to expand...

Hi,

The switch has an indicator light which illuminates when on - well it used to with the old lights as the same switch system that was in situ previously. It is soldered on to another earthing wire, as opposed to independently earthed.

Thanks,
J

mick the builder said:

Have you wired the relays correctly

Click to expand...

Hi,

I’m fairly confident I have:

30 - power source (from ignition column)
87 - output to spotlight
85 - ground
86 - switch

Drew it on the image with original post.

Sound correct?

J

IOWDoubleCab said:

Hi,

I’m fairly confident I have:

30 - power source (from ignition column)
87 - output to spotlight
85 - ground
86 - switch

Drew it on the image with original post.

Sound correct?

J

Click to expand...

Looks ok. Sure you haven't pinched a wire somewhere. Try disconnecting new lamps so no load and try again. Must be live to earth somewhere.

try removing the relay to eliminate it as faulty and the wiring to the lamps ( poss coil)
if this clear the fuse blowing then the fault is the relay or the wiring to the lamps if it still blows then the fault lies in the relay connections,switch connections
pict do help

NOTE IF YOU ARE TRYING TO USE A MODERN SWITCH SAY A YU000540LNF OR SIMILAR THIS TYPE OF SWITCH USES THE GROUND/EARTH SIGNAL

mystery said:

NOTE IF YOU ARE TRYING TO USE A MODERN SWITCH SAY A YU000540LNF OR SIMILAR THIS TYPE OF SWITCH USES THE GROUND/EARTH SIGNAL
View attachment 184987

Click to expand...

Hi mystery,

I'm using a simple mini rocker switch like the below.

• The +ve for the switch is powered by the cigarette lighter
• The earth is spliced in to an earth wire on the hazard lights
• The output runs to the relay (86)

Otherwise will run through your suggested actions in a couple of weeks when back home as away for work to see where the fault lies within the wiring.

J

the ground/earth is the gold tab and what ever config is dependant on which pin you use as the feed led on all the time or led on when switched
the only thing to watch out for is that you use shrouded tabs to stop the ground and live or switch wires touching when the switch wiring is tucked away behind the dash

mystery said:

the ground/earth is the gold tab and what ever config is dependant on which pin you use as the feed led on all the time or led on when switched
the only thing to watch out for is that you use shrouded tabs to stop the ground and live or switch wires touching when the switch wiring is tucked away behind the dash

Click to expand...

Thanks. Using shrouded connectors but will double check no contact alongside all the other processes you suggested. Will let you know how I fair in a couple of weeks!

Hi all.

Just to let you know I have fixed the problem. A small nick in the switch wire was touching the chassis behind the dash which was causing a short to ground. It blew out the diode in the relay so those needed to be replaced, but lights all working now. Replaced all the connections with shrouded connectors to be sure and checked the entire cabling for any other nicks but all good.

Thanks for your help!

J

Nice to know you are sorted