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NFIN02



Member Since: 17 Feb 2022
Location: Londonderry
Posts: 96

United Kingdom 1989 Defender 90 300 Tdi HT Chawton White
Spotlight wiring question
Just bought 4x britpart 8’’ spotlights for my expedition roof rack. Have them mounted but I am useless with wiring. Each light has 2 bullet connectors, can I get specific harness or will I need to make up my own. Each night is 100watt. Some lady bird guidance required please. I have already a switch, relay and fuse set up, just need help with connecting lights together
Post #1023538 4th Feb 2024 2:50pm
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custom90



Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20282

United Kingdom 
400w load total @ 12.2v = 32.78A Current Approx

You should be able to use 1mm2 cable for each individual spotlight wiring in parallel, but the supply I’d recommend 4mm2.
1mm2 supplying each spotlight, but the supply incoming 4mm2.
Use 4mm2 for the main ground also.

Automotive thinwall cable would be ideal, don’t forget to use a 40A make break 4 pin, type B, Normally Open contacts, Relay, and I’d fuse at 35Amp ATO within 20inch max of the battery live or source of the power supply.
Fusing is safety critical and is a must.

Regards fusing, I’d suggest an ATO inline fuse holder with a cap and relays wise Durite do very good ones, with Diode 4 pin make and break would be ideal and follow online generic wiring diagram.
Then from there you can work out where you want to take your trigger from, I’d recommend from main beam live, but you can use a switch or both if you want but will be more involved with wiring it all up.

Hope that helps.

Supply input / output:
Relay pin 30, input fused @ 35A ATO 4mm2. (From fused battery live or other power source).
Relay pin 87, switched output 4mm2 (to spotlights).

Trigger, turning relay on and off:
Relay pin 85 negative ground
Relay pin 86 live incoming trigger, from main beam as an example.

Heatshrink terminals are probably best for waterproofing at the spotlights. ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️
Post #1023593 4th Feb 2024 9:01pm
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NFIN02



Member Since: 17 Feb 2022
Location: Londonderry
Posts: 96

United Kingdom 1989 Defender 90 300 Tdi HT Chawton White
Thanks for the info. I literally just bought a few metres of 2x28 flat twin core cable to hopefully start wiring up parallel. Hope I am on the right track?
Post #1023656 5th Feb 2024 2:58pm
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NFIN02



Member Since: 17 Feb 2022
Location: Londonderry
Posts: 96

United Kingdom 1989 Defender 90 300 Tdi HT Chawton White
Hi all, I am doing something silly here I know but I need someone to put set me on the right path. I eventually got my 90 back on the road and took the challenge on of wiring up the front spots as per previous post. I have my spots wired up and down into the battery box with the appropriate wire size etc. got the online fuse fitted on the red/live line about 6 inches from battery. Got my 4 pin relay, and attempting to wire up by

Relay pin 30 power in.
Relay pin to spotlights


Relay pin 85 negative ground - just to door post
Relay pin 86 connected to existing switch on dash but switch appears to be power off another switch.

Am I being silly or do I need more than one ground? I am just getting a little confused about negative wire from lights, negative terminal from supply. Doo ground both of same locatio??
Post #1044152 28th Aug 2024 5:35pm
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custom90



Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20282

United Kingdom 
One for the Relay if you are using a live in trigger, one ground for the spotlights. So long as both are on a good common ground that is clean and low resistance all is well with that.
Unless the Relay has a diode on the trigger coil, you can use the coils for live or negative switch. ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️
Post #1044156 28th Aug 2024 6:09pm
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