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Rear marker lights and brake lights not working. But turns, 4 ways and reverse are working.


Rotorhead

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55 minutes ago, Jaydrvr said:

Yes, but you can often tell if the circuit is working by checking the trailer plug. That would isolate the problem to the light and its fixture. Jay

Duh.  That went right over my head.  Wish I had thought of it.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
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Hello all,

I haven't checked the trailer plug yet. I can do that tomorrow. I believe it was the lower right wire that needs to be checked right? I wish the diagram posted by hatrack was more detailed as to wire colors and functions for us non-electricians. hahaha.

 

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On 6/30/2021 at 6:47 PM, Rotorhead said:

I decided to pull the lights and get a look at the filaments. (should have started with that). The picture isn't the greatest due to small file size but you can see the higher filament is definitely not the same as the lower. It appears to be connected but something happened to it. It is the same on both fixtures. So I ordered two more Type 60 incandescent fixtures. Hopefully that is my problem. Now the question is will the LCM need to be reset? Will it reset itself during the self test when you turn the key? There are no LCM faults. 

I did learn that the turn and 4 way share the lower filament, which means the marker and brake share the upper one.

rear light.jpg

The upper large filament should be the stop, turn and 4 ways.  The lower smaller filament should be tail lights.  The larger filament makes for a brighter light, that's why the stop, turn and 4ways are always brighter then the tail lights on a vehicle. 

 

"It is better to have more truck than you need than to need more truck than you have"

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12 hours ago, Jaydrvr said:

Yes, but you can often tell if the circuit is working by checking the trailer plug. That would isolate the problem to the light and its fixture. Jay

I don't know about Volvos, because I haven't had to work on the trailer lights on my truck.  But I had a fleet of KWs back in the day and they ran a separate circuit for the stop lights for the trailer.  The tractor stop lights worked but no trailer stop lights.  Had to call KW and found they had a 40a inline fuse tucked in a harness behind the alternator, strange place to put a fuse. 

"It is better to have more truck than you need than to need more truck than you have"

2001 Volvo 660, Cummins 400 ISX, Eaton 3 Peddle Auto Shift    
2014 Fuzion 40' Toyhauler
2015 Smart Car                                                                                                                                                                          

                                                                                                            

 

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11 hours ago, dennisvr said:

I don't know about Volvos, because I haven't had to work on the trailer lights on my truck.  But I had a fleet of KWs back in the day and they ran a separate circuit for the stop lights for the trailer.  The tractor stop lights worked but no trailer stop lights.  Had to call KW and found they had a 40a inline fuse tucked in a harness behind the alternator, strange place to put a fuse. 

I suggested checking the trailer cord because sometimes you can narrow down which end of the circuit is not working.

 

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I was able to check the electrical connector for the stop light switch. It looked good. I was not able to get the switch itself off. I guess you need a special tool. Maybe something like the one for separating fuel lines etc...

I also cut out several very corroded splices back by the truck tail lights. I thought that would fix the marker lights, but, no such luck.

I really don't like chasing electrical problems. Not too good at it.

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But did you run a wire from battery negative to the light base?  It's usually the ground.  Chase the easy stuff first.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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Hello All,

Moresmoke, I checked the trailer electrical socket and I have 12.5 volts on two connectors located at the 10 and 2 o'clock positions when viewing from the rear looking forward.

My truck has a marker light interrupt switch. Is there anyway that that could possibly be the culprit?

Every single light is working EXCEPT the rear marker lights.

I am dropping it off next week to get the State Inspection done on it and see if they can locate the problem.

I may fiddle with it a little more between now and then.

Have a GREAT INDEPENDENCE DAY WEEKEND everyone!

Chuck

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I didn't run the wire from the battery negative to light base yet. Would have needed to go get wire.

However, I was out doing a Parked REGEN tonight and the rear marker lights were on. I figured I'd move the wires around and the lights blinked on and off. Then they went out. I had rewired the whole back end EXCEPT two splices. Perhaps on of them is bad. I will find out tomorrow. Got to go get some more splices and get to work. Hopefully the ground issue is with one of those two splices in the rear.

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The problem is finally resolved. There was one last hidden splice a few inches back from the flat 5 or 6 wire connector. There were actually two of these splices that were really bad. The blue/green powder that you get from copper.

So really I ended up re-wiring the whole rear lights and put in two new Type 60 light fixtures and a new LED license plate fixture. Should be good for years to come.

Thanks again for all the help. I sure learned a lot about my truck this week.

Chuck

corroded splice.jpg

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1 hour ago, Rotorhead said:

Should be good for years to come.

Just long enough for you to forget all about the wiring cleanup you just completed.

I have been wrong before, I'll probably be wrong again. 

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