Trailer brake lights dont work when headlights are on

Clean your connection points for the ground wires. Then connect the other end to bare metal of your trailer and see if they work properly.

Use a jumper wire from your common brown on the truck to your right and left plugs on the trailer end.

Trailer brake lights dont work when headlights are on. Trailer Brake Lights Do Not Work when Headlights Are On Question. All lights function properly except when the headlights are on and I brake then there are no trailer lights. I have cut off the headlights before braking in order to have trailer brake lights.

Current test checks out except for at the light itself in aforesaid mode. It is probably a ground issue. If the brake lights work with the heads off then I would not think it is a bulb issue.

When the heads are on it is grounding through the braketurn circuit. When the heads are off the braketurn grounds through the head circuit so you dont notice anything abnormal about the other lights. With the running lights on already drawing power stepping on the brakes adds even more draw on the system.

First to isolate the issue disconnect the trailer from the truck. Then use a circuit tester like PTW2993 if you do not already have one to test the connector on the truck. 5 Reasons Why your Brake Lights Dont Work When Headlights Are On 1.

If the light bulbs are shattered. Sometimes the fuse box and light switches are responsible 3. Check the Electrical Ground 4.

Is the wiring system responsible for brake lights fail. At last check the Turn Signal Switch FAQ. When the headlights are off the brake lights use the filament of the running lights as a sneak path to ground.

When the running lights are on that sneak path disappears. Take a jumper cable and attach to your vehicle. Then connect the other end to bare metal of your trailer and see if they work properly.

Helpful Expert Reply. On a trailer the brake lights and turn signals operate on the same wirebulb. So it is odd when the turn signals work but the brake lights dont.

There are 3 possible causes for this that are more likely than any of the other possible causes. First there could be a problem on the vehicle side. Brake lights do not work when headlights are on.

I was pulled over the other day by a Sheriff who informed me that my brake lights were not working properly. I discovered that the brake lights work just fine when the headlights are off but when I turn on the headlights they do not work. Trailer running lights which are on continuously whenever the vehicle headlights are on will draw more current than brake lights and turn signals which come on.

However based on your description of the problem - all trailer lights working until you turn on the vehicle headlights - there is one most-likely cause that should be easy to correct. This type of issue is typically related to a bad ground wire connection. Trailer lights work fine so long as the headlightsparking lamps are off.

Brake lights turn signals flashers and backup lights work perfect until I turn on the parking lightsheadlights. Ass soon as I turn on parkingheadlights none of the trailer lights work. Headlights on brake lights dont work.

Hold brake pedal down and turn the headlights on no headlights until I let off the brake pedal. -replaced headlight switch with brand new ac delco switch. When the running or headlights on the truck 2002 Ford Ranger are not activated the trailer will function pretty much normal except when using the left driver turn signal it also faintly causes the right passenger turn signal to activate so thats issue one.

2Issue two is when the running or headlights are switched on the brake light. Clean your connection points for the ground wires. Brush the metal with aluminum foil dipped in water reconnect enjoy your tail lights with headlights on.

Use a jumper wire from your common brown on the truck to your right and left plugs on the trailer end. The tail lights should come on respectively. To double check Take the jumper from a left or right on the truck and put it to the common on the trailer plug.

In theory with all things proper side markers and tail lights should blink. If youre testing the brake lights with the headlights on but the engine not running and obviously the alternator isnt charging the brake lights may not work. That would explain why they work with the headlights off and the battery voltage is closer to 12v.

Rod-Knox July 6 2016 101am 3. A bad bulb or a bulb improperly installed The. Turn on your running lights and check the lights wire on your truck.

Check the left and right turn signal etc etc. Start where the plug will plug at and if it works fine than its your trailer. But you said it worked with the other truck.

So I would just keep moving down on the truck on the headlight wire till it does not light up. If all the lights on the tester appear to function properly then the problem likely lies in the trailers harness or lights. If this is the case we move on to the next troubleshooting step.

Clean the connector plugs Before you begin the socket and plug should be cleaned using a. Trailer Running lights dont work- Turn and Break do. Jump to Latest Follow 1 - 16 of 16 Posts.

Battery charging power and tail lights but the turn signals and brake lights didnt work. All the lights worked on the RL. Blacked out Projector Headlights.

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The brake lights dim and the turn signals dont work with the head lights on. Headlights offeverything is fine. I have changed all the bulbs and checked the trailer connecter for corrosion it was clean.

The fuses are all good. What else should I check. Because the most common reason for trailer lights not working properly is a bad or missing ground check the trailers and trucks ground connection first.

A poor ground often becomes the culprit when only some lighting functions are working and when lights go. The most common reason your brake lights are not working but tail lights do is a bad light bulb. It can also be caused by a blown fuse bad brake light switch or issues with the wirings.

Your vehicles taillights are working fine but the brake lights dont come on when you press the brakes. 2003 Sienna tail lights dont work when headlights. Look under the dashboard next toabove the park brake pedal for the interior fuse box.

It has a black plastic cover. Remove the TAIL fuse and see if it is blown. This should get you fixed up.