Spotlight Voltage

Testing the voltage with the lights off is not much use. The correct way to do it is with the light on. The volatage should be no more that 0.5 volt less that the battery voltage. A bad connection with no current flowing can still show a reasonable voltage as the current rises so does the voltage drop.

To test take your jumper leads or other suitable heavy cable and go directly from the battery to the light, idally to the bulb directly if that can be done.

The lights you have should be brilliant. i really believe you have a voltage drop problem. As an indication I use 6 mm cable for my lights and it is far superior to the bought looms.

Hows it going Hughesy,

Not sure that the voltage drop across your wire sounds bad , although its not something I measure every day : )

Seeing you have a meter try measuring resistance of the loom , should be less than 1 ohm for such a sort run ( although I own a really cheap meter that reads 1/2 ohm for just the test leads ! )

If you have a lowish reading for your loom maybe you have a bad earth for your lights , make some jumper leads and go straight from the negative of the lights to the negative of the battery .

Some trucks use V24dc , is there a posability you have the wrong lights.

Hope this helps you out .

Glenn.

Mate if the light isn't connected you should have full voltage at the plug.

There must be a major resistance in the system somewhere to drop the voltage that much.

Test the voltage from the positive plug directly to the battery earth and if that is still low you have a high resistance somewhere in the positive supply.

You can check the Earth return the same way.

Hi Hughesy,

Do you have permanent power on one side and switch an earth through a relay to activate the spotties (sort of sounds like it by the description)?

If not (and I misread something) but you are checking the plug with your spotlights on (but not connected) with battery at 12.54V and you see 11.85V at the spotties plug (at the same time the battery is reading 12.54V) then you definately have an issue.

With no load connected (ie spotties), you should see the battery voltage at the spotties plug when you switch them on (0.1 - 0.3 of a volt lower still OK). When the spotties are connected, the battery voltage and voltage at the spotties plug should also be the same albeit lower as you are now loading the batteries.

Ideally the high beam activates a relay through a master switch that will apply battery voltage direct to the spotties providing a good earth return to the -ve terminal of the battery is there.

The most common issues in a situation such as this is wrong cable size (but you have a superloom), poor earth return (tech screw to body) or a poor connection (plugs, corroded terminals etc.).

Your multimeter is your best friend and a few checks will sort this out. Check resistance from spotty plug -ve to battery terminal -ve and also spotty plug +ve to battery terminal +ve (when spotlights activated and relay closed). This will diagnose a high resistant joint (poor connection). Should be 0.1 to 0.3 ohms max.

If it is correct then wire gauge could be too light and there is voltage drop. Connect spotty direct to battery (whilst in same conditions as your tests - ie engine off) and see if any brighter (take note of battery voltage though as you could have a crook battery as well and the load is dragging the voltage down). If so and providing the resistance checks were done then I would say voltage drop due to cable size.

There are quite a few things to check and I could keep typing for ages but start with those and see how things go.

Anyone else with suggestions?

Regards
David

cheap hid lights. i got a hid kit off ebay for 330$ and then bought a pair of ralley 4000 too. i put the hid kit in the ralley 4000 and there she is , hid driving lights for half the price

I've had a pair of Turini spots on my 100 for 7 years, and apart from a few blown bulbs, they've been great. I was looking at Lightforce 240's back then but didn't like the idea of having a black spot in the beam. They may be much better now, but the Turini's back then were comparable with the Lightforce. Sounds like you have a wiring problem,

Andrew

cibies, ancient history, get some rallye 4000, and see the light.