SwedeSpeed - Volvo Performance Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 ·
Electrical gurus... greetings.

Failed state inspection due to upper third brake light failure on my 04 V70. The upper third brake light is located in the spoiler.

Some background:
Three years ago my alarm kept randomly turning on and the door locks were acting erratic. I was able to troubleshoot it back to the wires concealed in the plastic housing in the hinge for the trunk door. A few wires were frayed or absolutely broken. I repaired them and all has been fine since then.

To the upper third brake light:
I am unsure if the upper third brake light has worked since the issue with the wiring in the hinge. I never knew the light to not be working, but it is absolutely possible that is hasn't worked the past three years. One of the wires broken during the incident three years ago was a yellow wire that supplies power to the upper third brake light. I traced this wire down to a connector above the driver rear speaker. It then traces to a yellow/red wire that is connected to the rear electronic module.

Upon recommendation of a mechanic, I purchased a new upper third brake light led strip and attempted to simply install it. I removed all surround plastic panels in the trunk area and I unplugged the green two wire connector in the upper area of the trunk door (where the upper third brake light directly plugs in). The connector has one yellow wire and one black wire which connects through a green connector to one red wire and one black wire for the upper third brake light. I prepared the new upper third brake light and temporarily installed it only to find it would not work.

I ran temporary positive and negative wires from the battery directly to the upper third brake light' red and black wires and the light turned on (also performed the same for the new upper third brake light and it also worked). The light appears fully lit. I disconnected my temporary wiring to the upper third brake light.

I then checked for voltage at the green connector I mentioned previously, while it was unplugged to the upper third brake light I received a range of 7.5 to 8 volts. I then plugged in the upper third brake light and tested for voltage and the green connector: I received .24 volts.

I then had a helper press the brake pedal in and I received .24 volts again at the green connector. I unplug the green connector and my helper pressed in the brakes I receive 7.5 to 8 volts (obvious<script id="gpt-impl-0.4917203031962931" src="http://partner.googleadservices.com/gpt/pubads_impl_79.js"></script>ly no voltage to the wires on the side of the connector which lead directly to the upper third brake light).

I checked for codes using a generic code reader, but there are none. I checked every single fuse in the engine compartment, the compartment to the side of the dash, and the rear cargo compartment. Every fuse is rated correctly and none were blow. I removed the positive terminal from the battery as a last line of wishful thinking... The upper third brake light still dot work when the brake pedal is pressed.

This is where my knowledge of troubleshooting this issue ends. Any further help is much appreciated and I am absolutely open to anything. Thank you. Ron
 

·
Registered
Joined
·
5,316 Posts
How difficult is it to run new wires and hard wire it to either the left or right brakelight just to get it to pass?

Post has me kind of confused. 7-8v sound low.
- with the connector unplugged the meter would read 7-8V across both wires when the brake switch is activated.
- Connector plugged in, meter would read .24v across both wires

Have you tested between both wires going up to the light for continuity? Tested each wire to a proper ground both with circuit ON/OFF?

Also keep in mind that LEDs are polarity biased.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #3 ·
I don't think it would be too hard to wire either brakelight to the led upper third brake light just to get is passed... of course, though, I would like to get it repaired and in working order. But if that's what I have to do, then I will.

I tested it just now with the connector unplugged:
8.5 volts connector unplugged
8.5 volts unplugged with brake pedal pressed in

With the connector plugged in:
.24 volts plugged in
.24 volts plugged in and with brake pedal pressed in

I am able to trace the yellow and black wires down through the trunk hinge into a gray connector with multiple wires and I have continuity for both wires at that point The yellow wire then becomes a yellow/red wire and I trace it to the rear electronic module and I have continuity of that wire. I can trace the black wire down into a white plastic channel under cargo pop-ups (the trunk floor, I guess). From there the wire extends towards the front of the car but I gave up disassembling the car because I thought if the wire extends to the front of the car, then I would just test it there. But I have to locate where the black wire begins. At the central electronic module?

I am very limited in my knowledge of electronics and I'm not sure how to answer the question "Tested each wire to a proper ground both with circuit ON/OFF?" But, if you tell me how to do it, I will. Thank you so much.
 

·
Registered
Joined
·
5,316 Posts
Sorry forgot that most of the lights on this vehicle always receive voltage when it's on, but with reduced current. This is how the CEM is able to monitor if the circuit is closed or open (burnt out/faulty lamp would cause an open circuit and would trip a code). If the wiring checks out then there may be an issue with the switching. Gotta trace it all out, even that black wire (might just be a ground, test for continuity with the body, if ~0ohms then it's ground), check exactly where that red wire attaches might be a faulty relay.

I'm mostly throwing guesses, never actually troubleshot the lighting on this vehicle, but there are only so many issues that can cause it not to work.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #5 ·
I will have to trace the ground back all the way. I got a hold of the wiring schematics and it appears the rear brakes run through the REM and a relay RMI15. The upper third brake does not. It appears to receive a signal/power from the brake light switch, then from the CEM through the REM.
This is where my lack of knowledge comes into play: if I suspect there is an issue with the ground wire, then couldn't I just run a new ground wire from the vehicle's body for the upper third light? And disconnect the existing ground wire?
 

·
Registered
Joined
·
5,316 Posts
http://www.volvowiringdiagrams.com/... V70 XC70 XC90 Supplement Wiring Diagrams.pdf
PG 34

10/19 is the third light

SB = Black, is tied to the same ground as the left parking light

YR is connected to D4 output on the REM.

I do not notice any wire going to the CEM for the third light (10/19)

10/3:2 has me confused. "10" indicates a light, "3:2" indicates a part ID. It's in series with the black wire. Have you noticed anything?
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #7 · (Edited)
I'm not sure if that's how my car is wired.

The diagram tells me that constant power from battery goes through fuse 11B/12, then through the engine compartment distribution box, into 3/9 the brake light contact. Then power runs to the CEM (yellow wire), then to the REM (green yellow wire), then to the 54/78 connector (yellow red wire), then to upper third brake light (yellow wire). The yellow wire actually runs to a connector not show on the diagram. Then the yellow wire becomes a red wire which leads directly to the upper third brake light.

The diagram shows that the ground wire is supplied at a junction with the rear left brake light, then to 54/78 connector, then to 10/3:2, then to the upper third brake light.
This is not how my car is wired. Working backwards, the upper third brake light ground goes to directly to a connector specifically for the upper brake light. Then the ground follows down through the hinge into 54/78 connector. It then goes down into the white plastic channel and that's where I stopped following it.

I don't know what 10/3:2 is. End of manual says 10/3 is license plat lighting. What's the ":2" of that?

https://www.dropbox.com/s/kslhsnwofgwyhw8/v70.jpg?dl=0
 

·
Registered
Joined
·
5,316 Posts
Here's what i get from the diagram

3/9 is the brake pedal contact.
11B/12 would be the control circuit to the coil of realy 2/72
2/72 controls circuit 11D/3
when 2/72 is on, then shunt 20/31 activates circuit 11D/14 to, switching on the left and right brake lights.

There must be something within the REM that activate the third brake light as both the 2003 and 2005 diagrams both show it as an independent circuit from the REM. only difference is with the 2003 black terminate to ground and 2005 black terminates to the REM.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #9 ·
I traced both of the wires up to the brake contact and both have continuity. What keeps puzzling me is the change of voltage when the upper third light brake connector is unplugged (8+volts), then plugged in (.24 volts). Antherzoll, your suggestion of tapping into the brake lights got me thinking... that I could tap into the trailer wiring harness. I was able to locate the 12 volt wire in the trailer wiring harness and the ground wire and verify power. Had my helper press on and off the brake pedal and was able to verify that I was receiving 12 volts when brake pedal was pressed in.
I simply ran new wires from the upper brake light down through the rear driver's side trunk hinge and all the way to the wiring harness. Then used some quick connectors/disconnect and tapped into the trailer wiring harness for the upper third brake light. Thought it might be useful in the future if I ever needed to quickly disconnect the upper third brake light (if, say, I was using a trailer and was concerned the trailer lighting would overload the circuit with the upper third brake light also in operation).
I would have liked to have solved the issue of the upper brake light not working, but I was spending a lot of time and I began to fear that there may have been damage done to the Rear Electronic Module a few years ago when the wires in the trunk hinge were broken.
Thanks for all your help, cheers!
 

·
Registered
Joined
·
1 Posts
That's a great idea to tap into the trailer harness. I've been battling brake light issues. The housings are all plastic and both have heated up at some point and partially melted, making the contact surfaces float such that they caused intermittent failure and finally...lights out. The bulb housing in one side doesn't fit right anymore either, and has to be backed off about 1/8 turn from fully engaged to work properly. I have tailgate not shut messages too, and suspect the D-pillar harness has some brittle wires.
 

·
Registered
Joined
·
1 Posts
I've been battling a very similar battle with my center brake light (in a 2007 V70R) after wire damage in the harness to the tailgate - which led me tonight to the same conclusion: much as i would like to address the core problem, i think that tapping into trailer connections might get me a working light. Do you happen to know/recall which points on the trailer connector you used?

cheers-
tim
 

·
Registered
Joined
·
9 Posts
Success!

I've been battling a very similar battle with my center brake light (in a 2007 V70R) after wire damage in the harness to the tailgate - which led me tonight to the same conclusion: much as i would like to address the core problem, i think that tapping into trailer connections might get me a working light. Do you happen to know/recall which points on the trailer connector you used?

cheers-
tim
I found myself in a similar situation with my 2001 V70XC having not passed the NYS inspection because of the 3rd brake light (actually, the guy didn't even start it as he noticed the light being out right away).

I was able to track down the severed wires and repair them but was getting no more than 6v to the light. I am never thrilled with the prospect of spending $600-$800 on a part like the REM, but was even LESS thrilled to do it just for a light.

Long story short: re-wiring that light to the trailer harness worked like a charm (it's the yellow wire running to the trailer harness for anyone who is curious).

Everything else seems to work fine so I'm glad I could find this workaround. Thanks for the tip!
 
1 - 12 of 12 Posts
Top