Third Brake light

rdaino

Member
My third brake light stopped working yesterday on the raised bar of my 94 d90. everything else electrical works. connections at the lamp appear to be good and the connections behind the passenger side speaker also seem good. i replaced the three bulbs. still not working. the sockets seem a bot loose but should operate. my next step was to put a meter on the sockets & the connection in back of the speaker. does anyone know which fuse is dedicated to the third brake light?
any ideas or suggestions would be grateful

thx

rob?
 

javelinadave

Administrator
Staff member
@rdaino ,
First you are your brake lights working?
If yes you need to see if you are getting current to the 3rd brake light. Use a volt meter but ground it to a good ground or even the battery negative.
If no you may have a bad brake switch or a fuse.
If you are getting voltage to the third brake light you need to clean up the bulb holder or make a new ground depending on
the situation.
 

rdaino

Member
appreciate the feedback. all other lights are working. only the third brake light has failed. i did test for power at the sockets of the third brake light and no power. connection looks good behind the speaker. can you provide the location of the ground wire so i can check?
 

javelinadave

Administrator
Staff member
I believe it is on the right ride based on the fact that the bar is hinged on the right side. If you have no power and assuming you tested it using a valid ground the ground isn't your issue.
I have to ask as you are trying to troubleshoot a very simple problem.......... Do you know how to use a volt meter properly? Do you understand how electricity works? I'm happy to help but I get the feeling something is being overlooked.
 

rdaino

Member
i know enough to be dangerous & i agree it feels something being overlooked but i had a engineer test the power at the lamp sockets!
i take a look again for the ground. when you say right side do you mean right side of lamp where the sockets are or some where at the connection in back of the speaker?
thanks for your help
 

javelinadave

Administrator
Staff member
The third brake light wiring should plug into the harness behind the right side, rear speaker.
Where did the "engineer" ground the volt meter? Did he test the ground for continuity with another part of the truck? Seriously, what you are trying to test is the electrical version of why isn't water come out of my garden hose.
 

rdaino

Member
so, i was not there when sockets where tested albeit the tester was more than qualified...that being said yes he could screw it up.
therefore i agree its gotta be something simple.
two pictures
1. shows the black and red connected for the power to the third brake light
2. possible a disconnected ground....if so where does it attach in back of speaker?

IMG_2315.jpg
IMG_2314.jpg
 

javelinadave

Administrator
Staff member
From memory the green is your turn signal and the red is your brake light.
If the wire circled is the wire to your 3rd brake light then be sure the black wire is fully seated into the connector. Also check that the red wires are also fully seated into their connector. If they are then test for continuity between the connector and the build holder, then test for voltage. If both have good continuity and voltage then you have a bad fixture or a bad bulb.
IMG_2315.jpg
 

RBBailey

NAS-ROW Addict
Callsign: KF7KFZ
Hope you have this sorted. I’ll just say that whenever I test power at a wire end or socket on a Rover, I go wherever I can first with something in that area that I know works. For example, you know your other rear lights work, test those first just to make sure you have a good ground. Then using that same ground, test the suspected socket, the wire leading to the socket, the base of that wire, etc…. Till you find the break point.

Sockets could look good, but be broken. I often don’t see where the break or corrosion is till I’ve pulled the thing out, and then it falls apart in my hand.
 
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