Weak wire voltage

[bkwapisz]

Just changed my taillights to LEDS because one didn't work, was completely sealed, and I figured the bulb was bad. Now everything works (as it was) except for that same light when the breaks/signal etc is on. The LED's glow faintly but not enough to see from a distance. Rechecked and replaced grounds, no difference. I have an alternating 12V when the hazards are on but apparently not enough current to fire the light adequately.

My question is this: Having checked everything else on the circuit, would it be most prudent (=easiest) to just replace the run to that light? I have the wire and the boat's off the trailer so now's the time to do it. I'm assuming there's a fault in that wire and frankly it'll take a lot to check the resistance from front to back due to length. BTW it's a 1990 Ranger Trail trailer.

Thanks in advance for any thoughts.

 

[royal0014]

Re: Weak wire voltage

Still sounds like a ground issue. On the one that isn't working, check the tab or plate where the light mounts. The mounting bolts are the ground contact, the bolt holes must be clean and free of paint, etc.

Possible, but unlikely, you have low voltage from the tow vehicle on that circuit. Put a meter on the plug.


<<)))(((>>

 

[dockwrecker]

Re: Weak wire voltage

If your ground wire from your light doesn't run directly back to the harness, that could be a big part of it. Many manufacturers ground the lights at the frame rather than running it back to the plug.

 

[bkwapisz]

Re: Weak wire voltage

If your ground wire from your light doesn't run directly back to the harness, that could be a big part of it. Many manufacturers ground the lights at the frame rather than running it back to the plug.

All the lights are grounded to the frame, including the one that is dim. I removed the ground, put a new, soldered connector on it and a new bolt to the frame. No rust there. I suppose what I SHOULD do is run a jumper from the vehicle connector to the light directly then go from there. Oh, and I also did the same with the main ground connector to verify it worked well. Bugs me though that all the other lights work ok except for this one, especially after a new light.

The lights needed to be changed anyway. They were at least 30 yrs old and looked original.

 

[ghamby]

Re: Weak wire voltage

check the LED fixture independently,(directly to a 12VDC source).
Meter between the feed to the fixture and the chassis. Use a decent meter.
A 12v bulb with bare end leads is helpful. The resistive bulb will load the circuit. Like all the guys said, it's probably the ground. Remember, polarity counts with LEDs.

 

[bkwapisz]

Re: Weak wire voltage

check the LED fixture independently,(directly to a 12VDC source).
Meter between the feed to the fixture and the chassis. Use a decent meter.
A 12v bulb with bare end leads is helpful. The resistive bulb will load the circuit. Like all the guys said, it's probably the ground. Remember, polarity counts with LEDs.

The connector is a 3-wire connector: one ground, one for the tailights and the other for the brake lights. If I connect the feed for the taillights to the brakelight connector the brake light works, which leads me to believe that the gound is ok and that the feed for the brake (brighter circuit) is at fault. I'm just going to try to shunt from the truck to the brake light connector to verify my hypothesis and then prob replace the whole wire.

 

[bkwapisz]

Re: Weak wire voltage

Well, after changing out ALL of the trailer wiring AND replacing all the grounds, turns out the 4-pin connector plug was bad. Oh well, at least I have better wiring now. :redface: