Brake/turn signal lights don't work, running lights do

My PUP was notorious for corroded lamp ground circuits.

Do you get voltage on the seven pin at the TV side of the circuit? The voltage at the Tow Vehicle's plug should pulse with the turn signal.

A battery changer is handy for energizing a single pin and tracing the circuit.

Good luck

You said the fuse looked good, but they can look good and be burned out. You need to test it or replace. But it would be strange if both left and right fuses would be blown.

Brysonh801 wrote:
I have a 1983 terry 30' trailer. A while ago when I first bought it the brake lights and turn signals did work, now I'm facing the problem where they do not work, but my running lights do work, any opinions on what could be causing this I replaced my fuses bad or not. Checked a few wires and clean trailer side 7 pin connector

You didn't say what the tow vehicle is. It's possible, you have more than one fuse box, and you may have replaced the fuses for the truck lights.

My F250 has two fuse boxes, one in cab and one under the hood. My trailering fuses are in the box under the hood, and there are separate fuses for brake / turn (left side, right side) and running lights.

I would suspect (in this order):

1. Burned out bulb
2. Corrosion in the bulb socket (you'll see this on step one)
3. Blown fuse (truck side)
4. Bad ground connection (trailer side)
5. Broken wire (trailer side)
6. Broken wire (truck side)

Most likely, you'll have it working before you get to step four. Please, let us know what you find.

Tail lights is a different circuit then the stop/turn signals.

Usually the running/marker lights are all on one separate circuit from tail/stop/signal lites. Seems to me the running lites on my last two TT's had green wires running to each one. White for ground.

Get this 4pin/7pin tester and see if you are getting power at the back of the tow vehicle. This eliminates 50% of the possible problems. You now know whether the problem is in the tow vehicle or the trailer.

4 pin/7 pin wiring tester

What kind of tow vehicle? Some have separate fuses for the trailer connector.
That age of rig used the metal skin for the ground.
Check under the tongue for a junction box. Check for power and quality of connections. Some rigs had fuses there.

Did you check for voltage at the tow vehicle socket? It's always best to start from the power source and work your way back.

Look carefully inside the light fixtures. Assuming your tow vehicle brake lights are still working OK, the most likely problems are bad bulbs or corroded sockets/connections in the fixture itself. If the tail lights work, the ground to the light assembly is good, it is shared with the brake/turn signals. Must either be bad bulb or the connections.

Just replace the bulbs.. Cheap and if that does not fix it, start checking ground wires.. That's usually the next easy thing to fix..

I once had a trailer where the brake and turn signals did not work, on both sides...

But the running lights worked fine...

They are actually 2 different wires and elements inside the bulb. Turned out, it was just the bulbs. After about an hour of checking all the wires, fuses and such, finally just put a new bulb in and BINGO.. Worked fine.. Just happened that both bulbs went out.

Go figure..

Good luck!

Mitch