1993 850 Brake lights

Benji40 · Post by **Benji40** » 17 Aug 2012, 20:28

My son informs me earlier today that he doesn't have brake lights and hasn't for a few weeks. After resisting the urge to debrain him I checked all the usual suspects. Only one socket on the passenger side was registering any voltage ~10. The middle light in the rear window does work. Checked the brake light switch by jumpering the two wires, the one hot socket did light up but nothing else. So I assume it is not the brake light switch. Do I have two bad socket boards or is there something else possibly going on?

Post by **rspi** » 17 Aug 2012, 21:11

It's no telling. That is not a usual problem. Try it with the head light switch in different positions.

Post by **Ben850** » 17 Aug 2012, 23:34

I also had intermttent issues with my '93 tail lights. There is a tail light control module under the drivers side(US) tail light. It is a blue box that is clipped onto a metal lip in the trunk. They upgraded that piece, because I found one at the pick and pull on a '96 that was about half the size, but performs the same functions, and has the same connector and wiring schematic depicted on the side.
Swapping them out seems to have taken care of the ghosts in my reverse and brake lights. A new one just showed up this evening that involves my turn signal slowing down when I hit the brake, with the lights on. I haven't checked it yet but I'm thinking this might just be a bulb.
Anyway, I'll post pictures of that module in the morning. Good Luck.

Post by **Ben850** » 18 Aug 2012, 07:51

Here is what the tail light control module looks like. I would suggest a junkyard replacement. You can see the difference a couple years of technology makes by the size.
I'm not sure if this is the cause of your issue, but if you can find one cheaply, it's not going to hurt.
Have fun.

Benji40 · Post by **Benji40** » 18 Aug 2012, 11:12

Thanks I think I will try it. Just wondering if the box could be bypassed and wired direct. Since it still needs the brake pedal depressed to work, would this be an option?

Post by **rspi** » 18 Aug 2012, 12:29

I doubt since it controls the "tail light" system. I don't know why Volvo complicated some things like this. SMH

Benji40 · Post by **Benji40** » 20 Aug 2012, 10:12

Got a call from a friend telling me that the Volvo had no rear lights last week. I had checked the brake switch under the driver's side, all the bulb sockets for current, and the blue box light control. I did find some loose connections and some light corrosion. Cleaned up the connections (on control module) and retested for current. They work now but I really don't know exactly what the original problem was.

Thanks for all the help from the forum including:

1.)Location of brake switch and how to test.
2.)Importance of the taillight control module.
3.)Where the important fuses are.