brake and blinker-nope, light-yes

[Skeetzee]

Flagstaff microlite 21FBRS..my driver side tail light is missing just the brake and blinker but the light works. I have replaced the bulb. Can anyone suggest how I troubleshoot? Thanks!

[llr]

Any corrosion on the connectors in the socket?

check at the trailer connector on the TV, this will isolate the issue to the TV or the trailer. You need a test light or voltmeter for this.

[Skeetzee]

never mind..I think I have a crappy replacement bulb.

[Oaklevel]

Hope that was it if not check the fuses in the Tow Vehicle.

[Skeetzee]

a fuse would cause one filament not to work? The lights work which is using one filament..the blinker and brake do not..the other filament. Will pick up some more bulbs today and see. My fingers are crossed that is all it is.

[spydunks]

I put a light coating of grease or dielectric grease on the metal parts of the bulb to slow down corrosion.

[windsurfdog]

And make sure you don't inadvertently force the new bulb in 180* from it's intended position. Always get a chuckle out of someone's tail lights under non-braking conditions where the intensity of one is as expected and the other looks like a brake light. Though not guaranteed to be the root of the problem, it is certainly viable a candidate.

[kenandterry]

Red Neck repair dot com says....

Problem: drivers side brake and blinker not working but running light works fine

Solution: switch bulb with one from passenger side where there’s no problem

Service Cost: uhhhh...got any beer?

[5picker]

Blonde joke...

A blond in the parking lot asks her friend (also a blond) if she would look to see if her turn signal is working. Blond in car turns on the turn signal and the blond friend standing behind the car says... "yes it is... no it's not... yes it is... no it's not." Blond in car says thanks for checking, I'll need to get that looked at!

Apologies in advance to the OP for the thread drift.

[Oaklevel]

Originally Posted by Skeetzee

a fuse would cause one filament not to work? The lights work which is using one filament..the blinker and brake do not..the other filament. Will pick up some more bulbs today and see. My fingers are crossed that is all it is.

It can yes........ and many TVs have separate trailer fuses. A 12V tester would help.

[DustyRoads]

I have a Tekonsha 7-Way Trailer Emulator Blade Style Connector it can test all connection on TV. It will also simulate load to test brake controler. Disclaimer they say it doesn't work for all brands of brake controlers.
It will let remove easily TV side. 12vt probe is always a must for every RV owner.

[DouglasReid]

For those of you who do not understand the vehicle/trailer wiring.

1. Both sides of brakes and signals on same circuit, use same filament in bulb

2. Both Tail lights on different circuit from brake lights, use second filament in bulb. ALL running lights on this same circuit.

You can easily troubleshoot the bulb and fixture by simply swapping the bulbs left and right without a test light.

1. If the bulb does not work in a fixture that the previous bulb did work, BULB BAD.

2. IF the problem is in the fixture even with a bulb that worked on the other side, FIXTURE BAD (usually a ground but sometimes corrosion)

ALWAYS use dielectric grease when installing bulbs!

Here endith the lesson

[jimmoore13]

Originally Posted by Skeetzee

a fuse would cause one filament not to work? The lights work which is using one filament..the blinker and brake do not..the other filament. Will pick up some more bulbs today and see. My fingers are crossed that is all it is.

Signals/Brakes are one circuit, and tail/marker lights are another. It's likely all are fused separately.

[Oaklevel]

Originally Posted by DouglasReid

For those of you who do not understand the vehicle/trailer wiring.

1. Both sides of brakes and signals on same circuit, use same filament in bulb

2. Both Tail lights on different circuit from brake lights, use second filament in bulb. ALL running lights on this same circuit.

You can easily troubleshoot the bulb and fixture by simply swapping the bulbs left and right without a test light.

1. If the bulb does not work in a fixture that the previous bulb did work, BULB BAD.

Troubleshooting

2. IF the problem is in the fixture even with a bulb that worked on the other side, FIXTURE BAD (usually a ground but sometimes corrosion)

ALWAYS use dielectric grease when installing bulbs!

Here endith the lesson

Sorry I disagree with your vehicle wiring findings the teacher is wrong.

# 1 is not true on all trucks my signals and markers are on a left side and right side fuse.

Troubleshooting

#2 just because the bulb worked on the other side does not always mean the fixture is bad could be a bad fuse or just a minor ground issue.

[jimmoore13]

ASSUMING IT'S NOT THE BULB...

An obscure option... Ground is a big deal. RV lights are usually affixed to the trailer body...often fiberglass or similar...so they need a ground wire that goes from the light fixture to some part of the chassis or a part of the trailer that's grounded to the chassis.

Is this a ground problem? The easy test is, turn on the tail/marker lights. Hit the 4-way flashers. If the tail light on the "broken" side dims, trace the ground wire and check the connection...usually a sheet metal screw in the trailer frame.

Turn signals demand much more power (much brighter filament) than tail lights. If the ground is bad, the tail light might not APPEAR to light up (it may be very dim), but the tail lights could appear normal. When you turn on the 4-ways, both signal/brake lights will attempt to come on. If the ground is bad, the tail light on the "broken" side will dim, and it will be even more apparent when compared to the tail light on the "good" side.

NOW TO CORROSION: Most "modern" connections are made with crimps rather than solder. If the little nub that makes contact with the bulb goes through the fixture to a corroded connection, nothing will work as it should. Pull the fixture from the camper and inspect it. If it's corroded, you might repair it, but you might be better off replacing it. Most trailer light fixtures are off-the-shelf items, and finding an exact replacement will not require a trip to the dealer.

FINALLY, if the TV turn signals work, and if you can use a multi-meter to verify that your 7 pin connector is delivering signal (put the black lead on any ground (like the trailer hitch) and probe each terminal in the connector looking for signal. If you have signal at the TV 7 pin connector, the chances are VERY good that the problem is at the light fixture on the trailer. There is an EXTREMELY UNLIKELY chance that your trailer wiring snagged on something and one wire broke, but typically, those wires are bundled in pairs, so snagging one would snag the other. Very unlikely.

[Oaklevel]

Tin / Aluminum sided RV the marker lights are often grounded to the tin. Tail lights rarely grounded to the frame. Usually the tin is grounded to the frame somewhere.

[jimmoore13]

Last thought. If you have incandescent lights (not LEDs), remove the bulb and shine a flashlight through it from BEHIND the light. This is also the best way to check fuses.
With the light shining through from behind, even the tiniest break in the filament will be revealed. Also look for discoloration. If you see black or dark brown anywhere on the filament, it's likely blown.

You can also use your multimeter (set to OHMS) to test continuity between the contacts (little bumps on the bottom of the bulb) and the metal shell...the ground. If you have continuity (a continuous circuit) on both filaments, the bulb is fine.

Don't have a multimeter? Buy one. You need it. All of $10 to $12, or free at Harbor Freight with one of the flood of coupons they send all the time. The HB multi-meter won't be much, but most DIY electrical tests are "Yes/No". Precision isn't all that important unless you're monitoring your battery condition. Continuity tests and "Do I have voltage?" are yes/no questions.

[mnoland30]

I purchased a 2009 ROO a couple of years ago and replaced both tail light fixtures with exact replacements because of sun damage. Already, the new ones are giving me problems. I wish I had spent a little extra money for LEDs. Better light, faster response, less chance for corrosion problems.

[timfromma]

Originally Posted by Skeetzee

Flagstaff microlite 21FBRS..my driver side tail light is missing just the brake and blinker but the light works. I have replaced the bulb. Can anyone suggest how I troubleshoot? Thanks!

These bulbs have 2 filaments. One is brighter than the other. The brighter filament is used for brakes and directionals. The dimmer filament is used for running lights.

[Mr. Dan]

Originally Posted by Skeetzee

a fuse would cause one filament not to work? The lights work which is using one filament..the blinker and brake do not..the other filament. Will pick up some more bulbs today and see. My fingers are crossed that is all it is.

This is the OP's last post to any place on this forum. Hopefully, the problem was solved.