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Brake Light Malfunction

Help, Advice, Owners' Discussion and DIY Tutorials on S40 and V40. In this forum you'll find S40/V40-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos.

1996 - 2004 S40
1996 - 2004 V40

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zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Brake Light Malfunction

Post by zulu-v40 »

Symptoms:
Brake lights turn on when pedal is depressed and car is off.
Brake lights don't turn on when pedal is depressed and car is on.
Cruise control will not engage.
Fuses are not blown.
Bulb failure indicator light is lit on dash.

I replaced the brake light switch, which did not solve the problem. Any ideas? I am stumped.
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Post by zulu-v40 »

When I'm underneath the steering wheel and depressing the brake pedal, I can hear something switching on and off underneath the radio near the gear shifter. So, it sounds like the brake pedal switch is functioning, but I still can't figure out why the brake lights do not function when the car is running.
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

jimmy57
Posts: 6694
Joined: 12 November 2010
Year and Model: 2004 V70R GT, et al
Location: Ponder Texas
Has thanked: 4 times
Been thanked: 320 times

Post by jimmy57 »

the click is your shifter locking mechanism, the thing that keeps you from moving gear lever from Park until brake is depressed.
In the dark have someone start the car and watch the tail lights closely and then apply the brake. I'm suspecting a bad ground and the taillights being on is killing the back feed grounding the tail light bulbs provide when not powered.
Does the upper brake light work at all?

zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Post by zulu-v40 »

The upper brake lights do work, but only when the car isn't running. I've had someone watch. The bottom brake lights stay on all the time when the car is running (even when switching out of daytime running lights mode). The upper lights do not light up at all when the car is running.
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Post by zulu-v40 »

When the car is off, if I depress the brake pedal, both window switches light up... Just discovered this in the dark tonight. When held for a few seconds, not only do the window switches light up, the stereo turns on.
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Post by zulu-v40 »

It would appear I've located the problem. I tore apart the tailgate looking for a rear electronic module, which I'm not sure even exists, and in doing so discovered the wiring harness for the tail lights was touching the nut located directly above in the picture. I'm not sure if that nut is grounded, or if that even matters, but clearly the harness did not fair very well...
location.jpg
location.jpg (197.49 KiB) Viewed 2962 times
Here is a close up of the mess:
wires.jpg
wires.jpg (193.93 KiB) Viewed 2962 times
So, my big question is what do I do next? Can I just splice new wiring in with crimp connectors and call it good?
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

zulu-v40
Posts: 123
Joined: 9 August 2011
Year and Model: 2003 V40
Location: Lansing, MI

Post by zulu-v40 »

I believe this is the harness and part number.
http://tinyurl.com/83tfyy5

Upon further inspection, there appear to be 16 wires, two of which are of a thicker gauge (red and black in color). I think it would be more cost efficient to do the wiring myself. Thoughts anyone?
2003 V40 T4, silicone vacuum hoses, K&N air filter, iPd Boost Gauge, iPd HD TCV, PowerSlot Rotors

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