No Trailer Brake Lights/Turn Signals - Montana Owners Club

ADP1723 · 09-12-2021, 02:27 PM

Sorry for completely editing/redirecting this thread, but I realized that I'm actually looking at a completely different problem now that I'm checking things properly and my 7-pin tester shows that everything is good on the truck side. So here's where I'm at with my 2007 montana mountaineer 342pht trailer lights issue, :

Currently my Trailer brakes/brake controller and the two front running lights on trailer work. However, the Trailer brake lights/tail lights, turn signals, and rear running lights do not work. I used my multimeter to test the rear tail lights and I get no voltage. Therefore, it seems like all the light wiring is good until you get past the rear wheels. Does anyone have any info on where this wiring splits off, or if there are any common culprits for this type of issue?

*Also, you may have seen one of my posts from a few months ago, where I had some rats chew through my slide-out wiring while the trailer was being stored. So I think there's a real good chance that some of the wiring (towards the rear of the trailer) could have been chewed up, and that's why only the front running lights work. So I guess my second question, is how the hell do I access this wiring? Do I just cut through the black plastic material that's covering everything up?

**Carl n Susan** · 09-12-2021, 04:36 PM

This is a somewhat conflicting Post but here goes. You wrote "No Trailer Brake Lights/Turn Signals" and then wrote the 7 Pin Plug is missing power on the 12V pin and the left turn signal.

Both the 12V (which charges the battery) and the left turn signal lines are fused in the Ford engine compartment. It is not uncommon to blow those fuses. Once you get 12V on all the pins of the connector, it is time to go after the other missing elements.

Are both brake lights inop? They each have their own circuit.
How about the tail lights? They share one circuit.

You can start at the tail lights or the front junction box on the pin box. Check for 12V and work forward/backward until you can find the problem. The brake/turn signal lines run directly to the rear. The tail light circuits branch off to the side maker lights on the way to the rear fixtures.

MARK A · 09-12-2021, 06:27 PM

My 2012 has no power to the trailer plug unless the key is on.

ADP1723 · 09-12-2021, 06:44 PM

So I realized that everything on the truck side is actually good after testing the 7-pin connecter in the bed with the truck on and the trailer cable plugged into the 7-pin connector on the rear bumper (when testing like this, all of the lights on the tester show everythings working fine).... so here's where I'm at now:

Currently my Trailer brakes/brake controller and the two front running lights on trailer work. However, the Trailer brake lights/tail lights, turn signals, and rear running lights do not work. I used my multimeter to test the rear tail lights and I get no voltage. Therefore, it seems like all the light wiring is good until you get past the rear wheels. Does anyone have any info on where this wiring splits off, or if there are any common culprits for this type of issue?

*Also, you may have seen one of my posts from a few months ago, where I had some rats chew through my slide-out wiring while the trailer was being stored. So I think there's a real good chance that some of the wiring (towards the rear of the trailer) could have been chewed up, and that's why only the front running lights work. So I guess my second question, is how the hell do I access this wiring? Do I just cut through the black plastic material that's covering everything up?

jcurtis934 · 09-13-2021, 08:11 AM

Drop the plastic bottom material and you should be able to see any wiring chewed on that needs to be repaired. The tail light wiring may be in the bottom or may be routed to the tail lights thru the ceiling. If you remove a tail light fixture, you should be able to see if the wiring goes upward or straight back and downward. Needless to say, any chewed wiring can be a fire hazard...tail lights not so much, but what else was damaged by the mice/rats and might be a fire hazard.

Daryles · 09-13-2021, 10:32 AM

I had to change both brake/turn/back up, lights due to water leaking into them and subsequent corrosion.
Behind the left light was a wad of wiring and terminal lugs. Very difficult to get it all stuffed back in the hole.
This is the junction for the left and right tail lights.
Here's a diagram. Hope this helps.

ADP1723 · 09-16-2021, 10:09 PM

this is great! Thank you!

BB_TX · 09-13-2021, 11:15 AM

If the diagram in any way represents the wiring path, best guess would be the wire bundle goes thru the ceiling front to back, connection branches to the front marker lights, farther back connection branches to rear marker lights, back to center light at top of rear cap, over to left (street side) and down to left stop/tail light assembly, across to license plate, and over to right stop/tail light. Maybe keystone or a visit to a local RV repair shop service manager might confirm the routing.

Loss of a single light could possibly be a loose connection. Loss of multiple lights would mean a simultaneous lost connection in multiple wires. Not as likely to be simply a bad connection. Rat/mouse theory certainly a likely possibility since you have already had that problem.

No good idea on where to start troubleshooting. I guess the first the first thing I might do would be remove one or more 12 volt ceiling light fixtures and see if you can find the trailer tail/stop light wire bundle mixed in the wiring path with the inside light wiring. Would seem logical they would run them thru a common path. But a lot if things they do is not what I would call logical. If you can find it at 2 or 3 light fixture locations then you could probably find the area of lost power. A soft tug on the wires should quickly reveal loose and broken or chewed wires. Then maybe fish new wires between those two points. Getting thru insulation and frame members will obviously be tedious. Otherwise I have no idea on how to trace wiring thru the ceiling.

**Carl n Susan** · 09-13-2021, 11:48 AM

I thought the wiring bundle for the trailer lights ran in the belly along the left side. Pull the left rear tail light and check. On my 2012 I would swear the bundle went underneath. But I could be wrong or they could have moved it.

BB_TX · 09-13-2021, 12:15 PM

Quote:

Originally Posted by Carl n Susan

I thought the wiring bundle for the trailer lights ran in the belly along the left side. Pull the left rear tail light and check. On my 2012 I would swear the bundle went underneath. But I could be wrong or they could have moved it.

That would certainly make it easier.

Daryles · 09-13-2021, 12:15 PM

I believe Carl is correct. The diagram is just that. Not a wire routing guide.

ADP1723 · 09-16-2021, 10:11 PM

Yea from where I've traced from the front so far, it does seem like the wires run under the belly rather than through the ceiling

bcrvman · 09-19-2021, 01:49 PM

Quote:

Originally Posted by ADP1723

Yea from where I've traced from the front so far, it does seem like the wires run under the belly rather than through the ceiling

Just remember when cutting an access hole in the belly that it is 3 sided with the opening toward the rear. That way the wind when driving doesn't open it up again. Also cut very shallow and slow. Get a finger in to help as soon as you can since often a lot of wires and even hydraulic lines are lying on the belly pan.

jimcol · 09-13-2021, 12:22 PM

Hate to keep offering this as a suggestion but a toner and amplifier is a pretty handy trouble shooting tool. Similar to this but available elsewhere: https://www.amazon.com/Professional-...1556771&sr=8-9
I may be wrong but to me your symptoms as you describe them could indicate a lost ground somewhere along the way.

BB_TX · 09-13-2021, 06:54 PM

I would have guessed they would ground each light to the nearest point on the frame. But if they run a common ground wire all the way from the front to each light assembly a break in that wire would certainly create that loss of lights.

Daryles · 09-19-2021, 05:14 PM

At the rally I did the factory tour. The wiring goes from the pin box to the left (port) side of the rig and down the left underbelly side to the back left brake lights.
The running lights split off underneath somewhere from the left side and go to the right side running lights.

ADP1723 · 09-20-2021, 01:34 PM

Well I dropped the bottom of the RV on the "driver's side" just in front of the trailer wheels, and sure enough the entire underbelly looked like a rat orgy den from hell

. The green, white, and red 16ga wires (which run to the tail lights) were shredded to pieces in a couple spots, so I'm planning on using some spare pieces of 16ga wire to reconnect the two ends that have been severed.

HOWEVER, I now have the following questions for you:

1) There is also a thicker red wire (maybe 10ga) running along the same path as the brake light wires that had some bite marks but the internal wires are all still intact. I’m guessing I should go ahead and repair/replace this one too for safety reasons, but does anyone have any idea what this thicker red wire is for/what it powers??? (see attached picture)

2) I can almost access everything just by unbolting the bottom cover on the side and peeling it down (to avoid cutting into it), but there is this metal pipe running horizontally across the bottom that's preventing me from getting where I need to work, so does anyone know what this pipe is for, and if it's something I can disconnect to move it out of the way without causing problems? Here is a picture of the pipe:

Thanks so much for all the help guys! You are all amazing!

bcrvman · 09-20-2021, 01:39 PM

Quote:

Originally Posted by ADP1723

Well I dropped the bottom of the RV on the "driver's side" just in front of the trailer wheels, and sure enough the entire underbelly looked like a rat orgy den from hell

. The green, white, and red 16ga wires (which run to the tail lights) were shredded to pieces in a couple spots, so I'm planning on using some spare pieces of 16ga wire to reconnect the two ends that have been severed.

HOWEVER, I now have the following questions for you:

1) There is also a thicker red wire (maybe 10ga) running along the same path as the brake light wires that had some bite marks but the internal wires are all still intact. I’m guessing I should go ahead and repair/replace this one too for safety reasons, but does anyone have any idea what this thicker red wire is for/what it powers??? (see attached picture)

2) I can almost access everything just by unbolting the bottom cover on the side and peeling it down (to avoid cutting into it), but there is this metal pipe running horizontally across the bottom that's preventing me from getting where I need to work, so does anyone know what this pipe is for, and if it's something I can disconnect to move it out of the way without causing problems? Here is a picture of the pipe:

Thanks so much for all the help guys! You are all amazing!

The pipe is your propane line. Be careful! No idea what the red wire might be.

MARK A · 09-20-2021, 01:40 PM

Looks like a propane supply. You should be able to unstrap it and work around it.

Daryles · 09-20-2021, 02:10 PM

Propane pipe.
For the wiring, if not too badly damaged (just nicks), I would use "Plastic Dip" liquid tape.
https://plastidip.com/our-products/liquid-tape/
You might find it at your local hardware store.
I would guess the red 10 gauge wire is solar feed from the roof (if you rig is pre-wired for solar) OR, 12vdc supply line from the truck to your house battery. You could put an ohm meter on it and figure that out before you repair the wire.

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