bulb failure indicator

renzo · Post by **renzo** » 27 Feb 2010, 12:05

I have a 1997 volvo 850. about 82k miles. all mine.

when i step on brakes, the dashboard bulb failure light turns on. let go of brake pedal, off goes the light.

doesnt matter if headlights on or off.

all bulbs replaced (both stoplights and highlight). still does that.

i have reseated all the bulbs, and i have reseated all the connectors (i used to design hardware).

does the bulb failure detector ever fail?

is there a specification for current drain on this circuit (too much and fuse blows, too little and bulb failure light turns on)?

do i have to use a special and expensive "volvo only" bulb?

thanks

peacock · Post by **peacock** » 27 Feb 2010, 12:42

does it happen both when you are moving and when standing still pressing on the brakes?

Post by **januwan** » 27 Feb 2010, 18:19

I have similar case, it happens when I press on brake, the indicator turns on for a split second and then goes away. If I press again it does not turn on again. To see it again I need to wait for a while. I think it started after I was rear -ended few years back. I replaced bulbs on the back, contacts looks good. I have no clue what is going on.

Post by **mvsuzr** » 27 Feb 2010, 21:24

Here's a few suggestions:

Pull the fuse, clean the fuse and contacts and try again.

Try your hazard switch. If you don't get a warning light when the lights flash, it might be the brake light switch. (Not too sure about this one, though)

Try a couple of Volvo lights. Pricey but might be worth it if it gets rid of a nuisance alarm.
Or, borrow a couple from a friend for a test...

See if there's a relay for the brake lights. If you find one, have someone push on the brake while you tap the relay. If the light flickers or goes out, replace the relay. Relay contacts are common failure points.

Let us know if you find anything.

EddieH · Post by **EddieH** » 27 Feb 2010, 23:45

Check the contacts for the third brake light on the rear deck. Mine had become loose and worn over the years and I had the same symptoms you describe. After cleaning the contacts and gently prying up on them to make good contact with housing, problem was solved. Good Luck!

KEWROCK · Post by **KEWROCK** » 28 Feb 2010, 00:30

'99 V70. I have the same problem as one of the posts above. The light goes on for a split second every few minutes for no reason. It flashes so quick I only catch it in the corner of my eye. I also cleaned all the contacts and checked the bulbs. No avail. My car was also hit at some point.

Post by **pkc303** » 28 Feb 2010, 05:49

I had no light what so ever. Discovered that a wire on the Lamp Monitor had been chewed by a critter. It is located on the back left trunk area, just below the tail light. Mine is blue, with a bunch of wires coming out of it. I have an electrical diagram for the 1995 model of the unit, if you need it. In the process of removing the problem, so that it doesn't reoccur.

Post by **Sperry** » 28 Feb 2010, 09:04

Mine did it. The center brake light ground was loose. I yanked on it real hard, and the issue has not reappeared for over a year.

However, regarding your specific issue, I'd first guess the bulbs do not match, and there is different draw between the sides.
This should trigger the bulb indicator.

In addition, possibly a short is sending current somewhere it is not supposed to go. This might also throw the indicator.

Jellobmw · Post by **Jellobmw** » 01 Feb 2011, 08:57

My bulb failure indicator would also go off for a split second every time I stepped on the brakes.

I replaced the brake light switch last Friday, and problem has gone away.

I imagine I could have disassembled the switch, cleaned the contacts, reassembled, and solved the problem that way. But given the time it takes to get to it, the time to repair, and the safety factor, I decided to just replace it.

Jeff

cY2k · Post by **cY2k** » 26 Mar 2011, 14:10

Jellobmw wrote:My bulb failure indicator would also go off for a split second every time I stepped on the brakes.

I replaced the brake light switch last Friday, and problem has gone away.

I imagine I could have disassembled the switch, cleaned the contacts, reassembled, and solved the problem that way. But given the time it takes to get to it, the time to repair, and the safety factor, I decided to just replace it.

Jeff

I've got a similar issue (99 V70), and I've pretty much isolated that my brake light switch is faulty too... When I press the brake pedal, I can hear a faint click and then the brake lights go on. But sometimes, I don't hear that click and the lights DON'T come on. The switch must just be failing (~120k on the car, so I'm not surprised).

But, HOW THE HECK do you get it out? I've been reading my Haynes (which is thoroughly unhelpful in this case) and searching on here, and I can't find anything helpful. I just can't find a tab or anything that's holding that sucker in. It seems to be locked into the metal bracket REALLY tight...

Anyone have any tips or pictures or anything? Thanks.