Hi all,

Great to have this forum! I was wondering if anyone has encountered brake lights not lighting, but parking lights working. I've replaced bulbs with no luck. They both stopped illuminating at the same time.

Thanks for any observations/advice.

Regards,

Marc

 

It is helpful if you post the year and make of your car as they each have their own quirks.

 

It could be the bulb sensor relay. It is a red round cylinder looking relay and is located behind the ash tray on most Volvos.

 

Is the high-mount light in the middle working? If not, your brake light switch on the pedal could have failed. Otherwise I'd think that the problem would be in the wiring harness on the passenger side (of a 240). I've noticed that the 240's tail light wiring runs up the driver side of the car, then goes across the rear to the right.

 

Thanks for the reminder! It's an '87 240 DL Wagon.

 

Thanks for the responses!

- The car is an '87 244 DL Wagon.

- I'll check the relay tomorrow.

- Yes, high-mount is working. Is the wiring harness up front in the engine compartment or passenger compartment?

 

there are wiring harnesses throughout the car.

240 wagons, a common failure point is the wire bundle in the tailgate hinges.

the bulb out sensor is not a relay per say. further, its failure modes usually involve false bulb-out indications, NOT actual lighting circuit failure.

looks like the brake light circuit is pretty simple. power from battery to positive terminal (on left fender under hood) to fuse 7 to brake switch. from the brake switch, it goes to the bulb-out-sensor, and from the sensor, separate wires run to each of the 3 brake lights.

 

A year ago I had the same problem on my 940 and it turned out to be the red bulb sensor relay that was bad. I don't know for sure if this also applies to the 240's.

Pierce is right in that it is not really a relay but they call it one. I don't know why.

 

the 7/9's use essentially the same bulb-out sensor module as the 240's... they aren't all directly interchangable due to different pinouts and such.

the sensor is a bunch of counter-wound coils, like the left lamp might be wound clockwise while the right one is counterclockwise, these are all wound around a magnetic reed switch.... if the current in the left and right circuit are the same, then the magnetic fields cancel, so the reed stays open. the reed switch is wired to the bulb-out light on the dashboard.

if I was faced with a dead bulb-out sensor, I'd quite likely hack it open, gut it, and replace all the coils with jumper wires.

 

before sweating the bulb-out thing, however, some basic testing is in order.

get a volt meter, set it for DC Volts. black lead on a handy ground, and verify that both sides of fuse 7 are 'hot' (+12V) even if the car is switched off. to the right of the fuse panel are 3 columns of spadelugs. the right most of these 3 goes to the left side of the fuse (and is power input), while the middle and left spades go to the right side fuse clips, and are 'output'. fuse 7 should have a green-red wire on the middle or left spade. the input is the red wire to fuse 6 (fuses 6-10 are wired together).

that green-red wire goes directly to the brake switch at the brake pedal arm. pin 1 of thise switch should always be hot, pin 2 should be hot when you depress the pedal. pin 2 has a blue-red wire that goes to pin 9 of the bulb-out detector.

pin 5 of the bulb-out is a blue-black wire to the center brake light. pin 11 is a yellow wire to the left brakelight. pin 10 is a yellow-grey wire to the right brakelight.

 

Thanks!

 

Extremely helpful, Pierce. I'll get a volt meter and go through all over the weekend. I can replace most any bolt-on item and have done transmission and clutch replacement, but I am lost with wiring.