AxeHealey
AxeHealey HalfDork
8/12/20 8:27 a.m.

I'm rewiring my old trailer and doing so slightly differently than it was originally. Below is a basic diagram of the current situation. 


 

I wanted to avoid those splicing clips so I figured I'd wire it so I could avoid that. The junctions are male/female with the lights plugging into the harness. Some of the harness female connectors have two wires. What I'm showing here is the tail and marking lights - they're all on one circuit.

M1,2,3 and 4 are simple marker lights with 2 194 bulbs each. L and R are these.

M1, L,R, M3 and M4 all lit up just fine the first time with no separate ground for M2 (wired like M1). M2 did no light up. Power was running through M2 to R so I figured it had to have continuity but I checked any way, it does. I adjusted the little contacts on the bulbs, no change. Then I ran a temporary ground between M2 and the trailer. M2 lit up but everything was dimmed significantly. I figured it just wasn't a good ground so I changed things to match the diagram above with a dedicated ground for M2. Same thing, it all lights up but it's really, really dim.

Patrick made the good suggestion to swap the bulbs over to another fixture to see if the issue is in the bulbs. No beans. He also then suggested running a low amp fuse in line to see if it blows. It did not. 

As I drew in the pic, I'm testing this with a 12V mower battery. Last time I looked at the voltage, it was about 12.3V. So, not full up on charge but darn close. Am I just putting too much draw on it and that's what's dimming everything? 230CCA. That's the answer I've come up with but wanted to toss it out to the group.

 

stukndapast
stukndapast New Reader
8/12/20 8:44 a.m.

If your diagram is right, your wiring is wrong.  You have M1 and M3 wired in series which means the voltage on the downstream side of the lamp is lower than battery voltage.  Every light in the circuit has to be in parallel.  If you measure the voltage across each lamp as wired, you will see that the voltages across each lamp will be all over the place.  Each should be the battery voltage.

In other words, one side of each lamp has to be battery + and the other side has to be battery -, aka "ground".

No Time
No Time Dork
8/12/20 8:47 a.m.

Wiring the lights series will also create the same issue as Christmas tree lights, if one goes out they all go out. 

APEowner
APEowner Dork
8/12/20 8:54 a.m.
stukndapast said:

If your diagram is right, your wiring is wrong.  You have M1 and M3 wired in series which means the voltage on the downstream side of the lamp is lower than battery voltage.  Every light in the circuit has to be in parallel.  If you measure the voltage across each lamp as wired, you will see that the voltages across each lamp will be all over the place.  Each should be the battery voltage.

This.  The way that's drawn won't work.

californiamilleghia
californiamilleghia Dork
8/12/20 9:08 a.m.

what about adding a back-up light.......

and maybe a  wire for a back up camera on the trailer , 

I also plan on putting a light on the front of the fender so I can see it in my rear view mirror , 

then I know the lights are working  and it shows the edge of the trailer fender  when you need to park in a narrow space......

AxeHealey
AxeHealey HalfDork
8/12/20 9:56 a.m.

Understood. The diagram is correct. Thanks everyone for the responses.

I used to be good at this stuff... 

I still don't understand why M2 wouldn't light up at all when it was wired in series but, alas, back to the drawing board. 

WillG80
WillG80 New Reader
8/12/20 10:02 a.m.

Something to keep in mind, polarity matters with LED lights. Even little 12V lights. Make sure it's wired the right way around.

AxeHealey
AxeHealey HalfDork
8/12/20 10:16 a.m.

In reply to WillG80 :

I did get that much right... at least I'm 99% sure that I did. 

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