I had a "Brake Failure" light illuminated on my dash, so I took my 240 in to have the brakes looked at. While following me to the mechanic, my dad noticed the brake lights weren't working, which I'm hoping is unrelated (I drive in a densely-populated city every day and haven't been rear-ended or honked at, but I'm not sure how long the problem has been going on).

The mechanic said the brakes were fine, then when I asked about the brake lights they said that the circuit board in the trunk is corroded and they couldn't find a replacement part, so I'm out of luck.

I've been doing some research and I'm getting the impression that the circuit board he mentioned is for the tail lights, which are working fine.

I've also looked up some wiring diagrams, and I've not had much luck figuring out where the problem might lie, mostly because the diagrams I've found aren't very clear.

I'm hoping someone who has experience with the 240 brake light circuitry can help me perform a diagnostic and maybe point me in the right direction.

I've replaced fuse 7 with a fresh 8A fuse and that didn't help. Neither the lower 2 brake lights nor the one in the rear window are lighting when the brake pedal is pressed. No other dash lights are on, and I haven't driven enough since the inspection to know if the "Brake Failure" light is still showing up -- it was intermittent before.

Ideally, I'd be able to get my brake lights working again as well as whichever circuit causes an alert to appear so that I know if they go out again. Thanks for any help!

 

there's a switch on the brake pedal arm assembly that triggers the brake lights.

on a late-version(*) 1993 240, according to the Volvo Greenbook, the brake light circuit runs something like this...

1) battery + terminal w/ fuse holder, fuse Y(ellow) to red wire to main fuse panel fuses 7-10.
2) fuse 7 green-red wire to brake light switch on pedal.
3) brake light switch blue red wire to bulb-out-detector pin 9.

1992 and early 1993 are identical except for no "Y" fuse at + terminal. instead, a red wire goes from the battery + to the 'positive terminal' on the left fender well and a brown wire goes to the main fuse panel fuses 7-10.

past this, its 3 separate wires to the 3 brake lamps, so IMHO, unlikely all would fail at once.

so. I would find that brake light switch, find the blue-red wire, and hook up a volt meter to it (other end of meter to chassis ground). press the brake pedal, you should see power. this switch is right above the brake pedal, and mounted such that the pedal arm presses the switch in when you're not stepping in the brakes.

if you see power there when you are depressing the brakes, then its time to find the 'bulb out detector' which is a beer can shaped device with a round plug of a lot of pins, its located under the driver side dash, on its side, somewhere below the far left air vent. use a thin wire stuck in the back of the connector so you can probe its signals when its plugged in. you should see brake light power at pins 9 (blue-red wire from brake light switch), pin 5 (brown-black wire to 3rd brake light), pin 11 (yellow wire to right brake light), and pin 10 (yellow-green wire to left brake light).

from the bulb out sensor, the wires go through a 2 row 24 pin (2x12) connector thats somewhat near (but forward of) the main fuse panel, from there the harness goes under the driver door sill, to the back where it goes up and over the rear wheel well, and branches out to the two tail lights and the 3rd brake light. the brake light wiring colors should be the same on both sides of this connector.

re: your corroded circuit boards at the tail lights.... you can replace the entire tail light assemblies, with either Volvo or aftermarket ones, these will have new circuit boards, new sockets. its a simple bolt-in installation. (**)


(*) there's two versions of the last year 1993. late ones have a 4-fuse holder at the battery positive terminal. early 93's are identical to 1992's.

(**) I have these Alvo brand Estonian clone ones on our 240, they have been working fine for 5+ years. I replaced ours because the original plastic was getting cloudy and leaking water in.... Volvo 240 244 Tail Light One Pair Set with Black Trim 1986 93 Made in Europe | eBay

 

I was having the same issue with my brake lights three or so years ago, so like above I bought the aftermarket Estonian and they have been fine since.

 

@pierce, thank you so much for all the info! I can't stress how useful this is.

@Rich240, did you have the 3rd brake light out, and if so, did replacing the tail light assemblies fix that problem? I believe my rear brake lights are dual-filament bulbs serving as both tail and brake lights, and the dimmer filament illuminates when my tail lights are on, which is one of the reasons why I suspect the issue isn't with that circuitboard.

So, thinking it was probably the brake light switch, I went ahead and bought a new one, since it was pretty cheap. I removed the instrument panel and the knee guards to get at it. Before removing it, I pulled the leads off of the old switch and put them on the new one and asked someone if the lights were working. They said they were, but in hindsight I should've been a little more stringent in my questioning, because upon installing the new switch and having the same problem, it seems they may've thought my tail lights were my brake lights. At least, I doubt the new switch was working then but isn't working now.

So now it sounds like the problem could be either upstream or downstream of the switch, but I don't have a voltmeter or much experience with electronics, so I'm probably going to give up and take it to a mechanic in my area that specializes in Volvos. If they can't figure it out, then I'll probably buy the requisite tools and give it my best shot.

 

if the low filament is lighting when the high filament should be on, odds are very good there's a bad ground in the trunk, or bad connections between the lamp fixtures and the ground wires. Same thing any time the wrong lights light up, especially if they light dimmly.

on a 240 sedan, the tail lights are grounded just to the left side of the left tail light (car's left, not yours). on a 240 wagon, they are grounded under the left side rear pop-out floor panel near but a bit to the right the left tail light. Ground wires are usually black, but sometimes brown. I'd unscrew the grounds, and use a bit of emery cloth to polish both sides of all the eye-lugs, as well as the body surface they are grounded against, and for long life apply a drop of DeoxIT to each surface before reassembling.

 

My third light didn't go out.