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Boot light, switch, third brake light problems Topic is solved

Help, Advice, Owners' Discussion and DIY Tutorials devoted to the second generation C70, S40 and V50 Volvos -- awkwardly model year 2004 ½ onwards -- plus where to go for advice and discussion on Volvo's sporty C30 Coupe powered by Volvo's ubiquitous inline 5-cylinder power plant.
S40volvo2007
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Re: Boot light, switch, third brake light problems

Post by S40volvo2007 »

RickHaleParker wrote: Tue Jan 07, 2020 2:16 pm 10/19 = Third Brake Light.

ThirdBrakeLight.png
what voltage should it read 12v or lower?
S40volvo2007
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Re: Boot light, switch, third brake light problems

Post by S40volvo2007 »

RickHaleParker wrote: Mon Jan 13, 2020 6:37 pm Ground pin #5 on the third brake light, see if it starts working.

Take some pictures of the connector on the third brake light. I cannot find anything for pins 2 - 4 but it looks like there should be a power line.
Had a closer look and it seems that third brake light is working when braking but is very dim you can see it but only just. There is a green connector with a yellow wire and a black wire.
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Re: Boot light, switch, third brake light problems  Topic is solved

Post by RickHaleParker »

S40volvo2007 wrote: Sat Jan 18, 2020 6:20 am Had a closer look and it seems that third brake light is working when braking but is very dim you can see it but only just. There is a green connector with a yellow wire and a black wire.
Yellow (#1) is the power, measure the voltage.
Black (#5) is the ground, run a second ground to #5 and see if it brightens up.

Check the CEM electrical connectors. Make sure they are clean and in good condition. Even a thin layer of tarnish can cause problems.
1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000.
2004 S60R, B8444S TF80 AWD.
2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0.
S40volvo2007
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Re: Boot light, switch, third brake light problems

Post by S40volvo2007 »

Just an update, ground was fine but no luck with the third brake light, which pointed me to think I have a faulty led, so I grabbed a second hand one and installed, works perfect. Thanks for your help, that concludes my electrical issues with this great car.
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