Intermittant bulb failure

[skibo]

I've been having intermittant 'low beam failure' reports for some time now - always the left - the bulb does out for a while and then later heals itself. Sometimes turning the lights off and back on manually is enough to get it back. I replaced the bulb a few weeks back, but the problem remains.

Feels like a stuck relay - do the left and right bulbs have seperate relays? Can anyone tell me where the relay(s) are located? Looked at the fuse box under the hood and in the end of the dash and don't see it/them.

[Willy]

No separate relays for left and right, see pdf file.
The relays (2/62 and 2/63 are located under the dashboard, left of the steering wheel.
10/64 and 10/68 are the main beams, 10/70 and 10/66 are the dipped beams.
Willy

[skibo]

Thanks, Willi.

I was hoping I could swap the left and right relays and see if the problem switched sides, but now that I see the low beams are controlled in parallel, I think it must be a wiring or connector problem. Or maybe a ground - looks like the high and low beam on each side share a ground - I never use the high beams, so I don't know if they are having a similar problem.

I really need to get one of these Vadis disks.

[ForbesMarch]

Had same problem, try checking the connectors... like everything plastic on the Volvo, they wear out very quickly.

[skibo]

ForbesMarch - Did you find it was the connector at the bulb itself? That is the only one that gets 'excercised'.

Willi & other techies - I've looked at that schematic more closely. It looks like the high beams are connected across the battery voltage (~14Vdc) but the low beams have a single 'dropping resistor' in series with the pair of them (in the 20/27 componant), so that they see something less than full voltage. This could explain why, when 1 bulb fails, the other tends to fail shortly afterward - when only 1 of the parallel paths is complete, the current through that resistor is lower and the resulting voltage drop is lower, so that the remaining bulb sees a higher than normal voltage. This could stress it and cause it to fail more quickly. I may have to do some playing around with the multi-meter to test this theory.

Also, I wonder which one of those cryptic symbols are the current sensors - I assume that it uses the current draw to flag the 'low beam failure' message - probably the two marked 54/3LE, since it does not differentiate left to right - can only tell when the combined current drops in half.

[Willy]

You could take a look at the relays, if they are the same you can swap them as a test.
the wiring diagrams are not a part of Vadis, is is a separate pdf file. It is available for
free, let me know if you would like one (MY2003)
Willy

[skibo]

But, if only 1 side is having the problem and the relay controls both sides in parallel, that can't be it.

Thanks for the offer of the Wiring Diagram PDF. I sent you a PM. Should we also consider posting that in the resource section?

[tolgatt]

mine is the same way , i have checked the connector to the bulb and found out that the plastic connector has been hardened so much from the heat,it was broken,,
i tried to stick it back in temporarily,,everytime it fails, i punch the headlight and it comes back on :D
i have to find an easy way to replace the connector and im sure the problem will be gone

[wgriswold]

One of the connectors at the headlight assembly (I can't remember exactly which one) was brittle from the heat and broke when I had to replace a bulb. The connector completely fell apart and inside it were two metal push on plugs that I attached to the posts that the connector pushed on to. Does that make sense? Anyway it has been two years and all is good.

Occasionally I think about doing something to insulate the now bare metal connections but have not come up with something that I think will stand up to the heat. Anyone have any ideas to solve that?

[skibo]

Makes sense. I was looking at the other side last night ( the easy-to-get-to side ) and the plastic plug just seems to have 2 seperate 'female spade terminals' within it.

I don't see much need to insulate the terminals, as they are completely enclosed within that waterproof plastic housing so nothing can touch them. And the terminals on the bulb are stiff enough that they won't come into contact with each other.

And I also don't think it matters which wire goes onto which terminal.

[skibo]

Confirmed. Plug had become brittle. I cut what was left of it away and just put the 2 remaining spade clips onto the bulb terminals individually - they are far enough apart that i'm comfortable with them being uninsulated. (knock wood)

( Side note - As an engineer, I'm surprised and dissapointed that Volvo couldn't even get this right. Determining the temperature of a headlight and selecting a plastic that can withstand it is pretty simple stuff. My other car is the 4th 20 year old vehicle that I have used as a daily driver and I've never seen this failure before. )

[Aviator]

My other car is the 4th 20 year old vehicle that I have used as a daily driver and I've never seen this failure before. )

Are the backs of the headlamps on the other car enclosed like on the Volvo? You can buy those headlamp connectors you know....most auto parts stores carry them. You just have to solder them in.

Dave.

[skibo]

Are the backs of the headlamps on the other car enclosed like on the Volvo?

No, but in my world, before the enclosed headlight went into production, it would have been recognized that an enclosed bulb will run hotter than an open bulb, a test would be run to determine how much hotter, and the material for the connector would then be evaluated to see if it was up to the expected temperature, and if it was determine that it was inadequate a different plastic would have been selected.

When you are designing something that has to last for a long time (20-30 years for the stuff I work on), some things are hard to predict, (how many potholes will the car hit, how much gunk will accumulate in the radiator which reduces its effectiveness, what is the actual air temperature when sitting in a traffic jam surrounded by other cars ) but it seems to me that this one should have been easy.

I don't mean to harp on our friends in Goteburg - they got a lot of things right.

[billr99]

I think its all about recycling. With the current EU regs, all those plastic bits have to be recyclable (unlike some of the plastics used in past). So if you design a part that uses recyclable material, it is bound not to last 20 to 30 years, right? I've noticed on all my recent Euro cars (all built since '96) that a number of plastic components in the engine bay have crumbled exactly the same way my headlight socket and a vacuum hose retainer did.

Perhaps they should use the same stuff that the shakes on my 100 year-old barn are made of. Cedar! Kind of like the body-frames on old Morgans (actually these are oak as I recall) [thumbup] It lasts a long time, is organic and recyclable. Perfect.

[Aviator]

Yeah, that's probably the reason, but I wonder what the excuse was for the crumbling wire harnesses on the older 240s and 740s.

Dave.

[billr99]

Yeah, that's probably the reason, but I wonder what the excuse was for the crumbling wire harnesses on the older 240s and 740s.

Dave.

Yeah, good point. Something must have went on during that time period. I had similar issues with a '87 Porsche, a '96 SAAB, and a couple of VWs. Somebody's "brilliant" engineering idea or an accountant's push at reduced production costs I would bet.

Bill