No trailer lights or brakes on trailer

will your trailer lights and electric brakes work if the little battery on the trailer is dead? I have no turn signals or brakes but I do have tail lights.

(quoted from post at 00:38:27 10/12/23) will your trailer lights and electric brakes work if the little battery on the trailer is dead? I have no turn signals or brakes but I do have tail lights.

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The dead battery will not send a signal to engage the electric brakes. You have other issues if your lights are not working. Bad Grounds are suspect/CM

'' will your trailer lights and electric brakes work if the little battery on the trailer is dead?''

Yes, the little battery is used only in a break-away situation. You have a wire problem.

Yes they will all work if battery dead. The battery is only for engaging brakes if the break away switch is activated.

I'd test truck connector first to confirm it is working. I had a truck that I had intermittent light/brake issues with, wiring harness was chafed and it would ground out, I'd lose brakes every time it happened.

There is usually a junction box at the front of the trailer. Harness from the plug end to the front of the trailer is in a sleeve. Open the box and see how many screws are loose or wire dropped off some of the screws. I had this issue with the left turn signal early this year. I bought the trailer new and it is not that old.

Get a test light and check the plug on the truck first. If no power, check for blown fuses. If good on the truck side, as someone else stated it could be a ground problem or broken or bad connections in the trailer plug

This post was edited by geok on 10/25/2023 at 07:25 am.

Trailer light problems are quite often a grounding failure. if you have a set of jumper cables go from a clean metal contact on the tow vehicle to a clean metal
spot on the trailer. some trailers use a ground wire, not the frame, so in that case the jumper cables might not solve it, but it's a quick and easy check!

Sometimes a little corrosion either in the plug on the trailer or in the socket on the tow vehicle will prevent a good connection. I've taken an aerosol can of electrical contact cleaner and sprayed it into both components. Seems to help whenever I've tried it.

Hmm. If the ground is bad you shouldn't have any tail lights. In fact, if you have a bad ground it's possible to see both turn signals flashing together, since you can have a ground path through both signals and the tow vehicle lights.

If your tow vehicle is fairly new, it probably has a separate fuse for the trailer turn signals. Check that out. Also, if you have a factory trailer brake controller, it might control turn signal lighting as well as brakes.

What Mark B posted. I wasted a lot of time once on a trailer light problem when it was a blown fuse in the truck. Get you a trailer plug tester and test your truck's output first. Wherever trailer equipment is sold.

Fuses almost never blow for no reason. You STILL probably have a trailer wiring problem even if the fuse is blown. Most likely a pinched or rubbed-bare wire somewhere in the frame.

> Fuses almost never blow for no reason. You STILL probably have a trailer wiring problem even if the fuse is blown. Most likely a pinched or rubbed-bare wire somewhere in the frame.

Correct. Just be aware the trailer that blew the fuse might be a DIFFERENT one than the trailer you're troubleshooting.

Mornin Indiana, good question, I couldnt count how many trailers Ive owned and how
many had light problems over the past 50 years grrrrrrr SO OFTEN DUE TO A BAD GROUND
!!!!!!

1) will your trailer lights and electric brakes work if the little battery on the
trailer is dead?

YES ifffffffffff all else is okay ?????? the little trailer battery has to do with
powering electric brakes should the break away trip. Lights fed off the connector
are truck powered NOT via the trailer battery. Trailer brakes are NORMALLY powered
off truck orrrrrrrrrrrrrr little trailer battery if break away is tripped

2) I have no turn signals or brakes but I do have tail lights. (NOTE tail lights
working sounds like the ground is okay, but still cant be sure, maybe the trailer
bulbs are bad or there's still another grounding problem ??)

a) FIRST thing to test is if the trucks trailer wiring connector (often 7 or 6
pin round or 4/5 terminal flat) IS PRODUCING A VOLTAGE OUTPUT SIGNAL WHEN TURN
SIGNAL OR BRAKES ARE OPERATED ON THE TRUCK ???????? Check BOTH using the connectors
ground pin for ground as well as the truck frame itself. One of the connectors pins
is ground if alls well ?? THAT SHOULD BE IN PLACE

If NOT, are they working on the truck by itself ??? If NOT working on truck
itself look for a blown fuse or a TRUCK wiring issue ......If working on truck but
there's NO (Brake/Turn) signal at the connector, check wires on connector at source
and at connector itself for Brake/Turn signal. .......Ifffffff theres a good
Brake/Turn signal at connector, but no trailer Brake/Turn lights........

Check ground (trailer lights and at connector where one of its pins is ground)
......Check Bulbs..............Check wires all the way FROM connector TO trailer
lights.......Check BOTH connectors and all wiring connections, Ive seen so many that
are broke or corroded at the connectors

So often its a ground problem on the trailer orrrrrrrr a ground problem as wired to
the connectors ground pin,,,,,,,,,,,or a ground problem in the light
fixture,,,,,,,,,or a bad bulb.

NOTE I had MUCH better luck if I ran a dedicated ground wire TO EACH LIGHT FIXTURE
instead of only relying on the frame as the ground.

They make testers you plug into the connector to see if all its circuits are
working or else use a simple 12 volt test light or DC voltmeter. On many trailers
the ground pin on the trailer end connector is connected to the trailers frame

TEST AND INSURE THATS A GOOD GROUND AND THERES A GOOD CONNECTION FROM CONNECTOR TO
TRAILER FRAME Still fact the tail lights are working makes it seem ground is okay
????????

This isnt rocket science, a simple 12 volt test lamp or volt meter is all you need,
got to have the Brake/Turn signal on BOTH truck and trailer connectors, good wires
good grounds and good bulbs

John T

My brother had something similar happen to him earlier this year. We spent probably an hour or so checking the plugs and bulbs. Wiring on
trailer was all good too. I dropped the spare tire to start checking truck (Chevy) wiring and found where the wire harness was rubbing on
top of the spare tire since a plastic retainer had failed. It rubbed through one of the wires. Spliced it back together with a waterproof
connecter and everything works.

Can't speak for your trailer, But everything works on my 24' Dutchman Travel Trailer with the
batteries disconnected.

PS if its the old bayonet type bulbs I have seen them and their sockets badly corroded, check for that..

John T

I switched my utility trailer's lights over to LED last year. What a difference! Since they require very little current to operate, you don't need a good connection at the trailer plug for the lights to work. And there are no replaceable bulbs to burn out or corrode. On my boat trailer, I don't bother unplugging the trailer when launching because the LED lights don't mind being submerged.

OH they do mind, they just don't complain about it for sometime after the dunking.