Thread: one spotlight not working - getting 4 volts

Sounds like you have a high resistance join where the feed is taken from the first light wiring to the second light.

ok, thanks for the tip! do you know how I might fix the issue? would running a thinner wire to both lamps do the trick do you think?

as in, joining two, thinner wires to the thick 12v feed wire from the relay? i've had a look at lots of different wiring diagrams but none seemed to make it very clear on what sort of wire to use

Bi H, don't go with thinner wire as resistance increases .Thicker wire is better. Can you test the output at the relay? That might tell you something and lead you to the problem. Cheers, 130man.

Piggy back connectors are an invention of the devil, there should be a fatwa against them! Find the correct size crimp connector you can put both wires in at the same time, or get a relay with two output terminals (both marked "87"). Thickish wires, crimped with a proper ratchet crimper (not one of those el cheapo flat tin things) or solder all the terminals to the cables. Also make sure your earth connections are clean and tight.

Originally Posted by bee utey

Piggy back connectors are an invention of the devil, there should be a fatwa against them! Find the correct size crimp connector you can put both wires in at the same time, or get a relay with two output terminals (both marked "87"). Thickish wires, crimped with a proper ratchet crimper (not one of those el cheapo flat tin things) or solder all the terminals to the cables. Also make sure your earth connections are clean and tight.

I cringe at the thought of crimps, they are crap, take your crimp connectors and fill them with solder, while i have a set of ratchet crimps for emergency use in the bush I would never leave something in my car fitted with crimps permanently, you will have less voltage drop and less resistance in a connector if its soldered.

I would also advice against earthing to the bumper, Ive always run an earth back to the battery in my cars, it doesn't take much more effort and it well worth it.
always use the thickest wire possible to reduce voltage drop due to resistance.

splitting the wire like a 'Y' is also a better option than attempting to piggy back them.

Leroy

Originally Posted by Leroy_Riding

I cringe at the thought of crimps, they are crap, take your crimp connectors and fill them with solder, while i have a set of ratchet crimps for emergency use in the bush I would never leave something in my car fitted with crimps permanently, you will have less voltage drop and less resistance in a connector if its soldered.
...
Leroy

Seeing as I almost daily use crimp terminals in my work, and I have to stand by my work as 99.9999% reliable, I have to respectfully disagree with you. Good quality terminals (e.g. Narva), a good quality ratchet crimper and cable that fills the terminal will result in a connection more reliable that solder in most instances. With small wires you can double over the wire to fill the connector better. Fully insulated crimps give strain relief that is difficult to achieve with soldered joints. Solder is fine for inline splices with heatshrink though and that is where I most often use solder instead of crimps.

example of better quality fully insulated crimp terminals:

Crimp Terminals Utilux Blue Female Spade Fully Insulated Terminal Quantity 100 | eBay

Uninsulated type:

100 X 6 3mm Uninsulated Female Spade Push ON Crimp Terminal NON Insulated 1 5MM2 | eBay

There are some absolutely rubbish terminals that should never be used on a vehicle, such as plain brass ones, including most bought from electronics supermarket style stores.

ok guys thanks very much for your help! i'll get a relay with two terminal 87s then and run a fresh, properly connected wire to each lamp. if i can find some extra wire i'll run proper earths to the battery, although i tested the resistance through the bumper and the multimeter said 0Ω I suppose it'd be better if they were in side to avoid corrosion