Help for Unreliable combo brake turn signal light on trailer

Thanks for all the responses! I simply replaced both fixtures with cheap LEDs from Amazon. All seems to be working properly now :)

By the way, if they aren’t LEDs, replace them with LEDs. They’re brighter for a reason many people don’t consider: even if an incandescent bulb was as bright, by the time it’s 12V power goes through a bunch of small-gauge wire and a connector or two, it’s getting pretty weak power.
The LED doesn’t need much power and still shines at full brightness.

That’s also why you still want to own an incandescent 12V test light for troubleshooting.
LED test lights will glow on the faintest current, sometimes misleading you to believe a circuit is good when it isn’t.

If they are the dual element incandescent bulbs, I have had problems with them on utility trailers a number of times. And almost always with the thin copper strips making good contact to the bulb contacts. Tapping on the assembly would cause them to work. For a while. Always eventually had to remove the lens and bulb and slightly bend the copper strips ti make tighter contact.

IF it is a LED light assbly, odds are it is BAD. BUT, you need to pop it out and check the wire connections to the light. IF they used a Tap Splice, the splice is probably not installed correctly. Doug

This is what a tap splice looks like.

https://www.lowes.com/pd/Utilitech-20-Count-T-Tap-Wire-Connectors/999956682?cm_mmc=shp-_-c-_-prd-_-elc-_-google-_-lia-_-106-_-electricalaccessories-_-999956682-_-0&placeholder=null&ds_rl=1286981&ds_a_cid=112741100&gclid=CjwKCAjwybyJBhBwEiwAvz4G7xbRqXd2EAJr7sP0jHrCJ7Ekuf6bkDNxBUrNIMUasnohk6LJQMFG3xoC8HoQAvD_BwE&gclsrc=aw.ds

If it looks like the one in the pix below, they are a friction fit, no screws hold them in.



To remove, you take a flat blade screw driver, insert the blade between the light and gasket. Then pry the light out of the gasket.

This type of light is typically sealed and the lamps inside are not replaceable. In this case, you replace with a new oval module.

You might also be presented with a plug in on your existing light, that plug may be loose or corroded which can cause intermittent light operation. Push plug back on and or check and clean and corrosion you might find and retry the light.

If no plug in, then issue most likely is inside the module and replacing the module is the fix.

To reinstall, make sure gasket is installed and seated, then install one end into gasket opening then push and wiggle the remaining portion of module until it is firmly seated in the gasket.

Most lights set in a rubber gasket are simply held in by that gasket. You just pry it out.

When I had a 5th wheel, I had rear light issues that drove me nuts. It seemed the problem was related to the ground wire. I ended up removing the light can and soldering all the wire connections. I also tighted up the light bulb connection. If you are using the 1157 bulb its just sitting in the correct spot by a hope and a prayer. You may have to rework that area also.

Good Luck