Brake light bulb holder woes

[Georgeandkira]

You'd think it'd be real simple.....and maybe it is.

My 2007 V70 had a right brake light which had a melted holder. It was white-ish plastic.

I replaced it with a black one from an earlier V70. At one point I actually got it to "1/4 turn" into place. When they go in easily they really do just pop in.

The bulb (known good , new bulb) doesn't light.

How does one go about this?

[SwissXC90]

Multimeter and logic

[petey]

A good bulb is one that you can see light up. Each and every other bulb is duff till you prove otherwise. Many is the hour that I’ve chased any number of cables trying to prove a new bulb was good....

Jam a hammer between the seat and the brake pedal and get into the cluster looking for the feed. With the ignition off, the only live wire should be the brake light, helpful if you haven’t got a wiring diagram, but be aware that jamming probes into things can blow fuses.

If the holder melted, it might have bent a connector coming out.
So, check for a feed at the multi plug, then at the surface connector and then into the bulb holder. I suspect it’ll quickly become obvious, they usually do.

[Georgeandkira]

I copy what you're saying. I have the multimeter out now.

Does the multi plug simply unplug? I know, just get on with it.

[petey]

Soz, can’t help there I’m afraid, I’ve been ‘lucky’ to only have to change the upper ELB207 tail light bulbs and they hurt me enough.
You should start with the sink and trace your way back to the source, but I would consider looking for something odd visually first, but don’t waste too much time on trying to see it, the multimeter is absolute in these cases.

[Missing Lincs]

Brake light relays in the REM are also a known source of trouble when brake lights stop working. Depending on model year and whether they/it has been replaced before, your brake light relay may either be two single relays or a double relay in one package.

Melting suggest poor contacts rather than over current which would cause fuses to blow, saying that, fuses can fail just through age, so another place to look in the REM.

[ASt85]

Originally Posted by petey

Soz, can’t help there I’m afraid, I’ve been ‘lucky’ to only have to change the upper ELB207 tail light bulbs and they hurt me enough.
You should start with the sink and trace your way back to the source, but I would consider looking for something odd visually first, but don’t waste too much time on trying to see it, the multimeter is absolute in these cases.

Check the holder to make sure that the middle sprung connection is actually in contact with the bulb by levering it up a little, check also the bulb you have got is firm in the holder - many bulb caps are under-size and won't make a good connection - Georgeandkira often recommends using a dielectric grease make sure of a bulb is connected.

[BlueRubber]

Originally Posted by ASt85

Georgeandkira often recommends using a dielectric grease make sure of a bulb is connected.

Forgive my ignorance, but wouldn't dielectric grease prevent electrical contact as it is not an electrically conductive material?

[Longhouse21]

Originally Posted by BlueRubber

Forgive my ignorance, but wouldn't dielectric grease prevent electrical contact as it is not an electrically conductive material?

Interesting article here regarding the use of non-conducting and conducting greases:
https://www.w8ji.com/dielectric_grea...ive_grease.htm

[ASt85]

Originally Posted by BlueRubber

Forgive my ignorance, but wouldn't dielectric grease prevent electrical contact as it is not an electrically conductive material?

Yes, dielectric grease is non conductive, but I assume it prevents vibration thereby allowing better contact.

I have not used dielectric grease, but have used a smear of conductive copper grease on the bulb's tubular metal part side connection of a lamp to improve the connection, much as you would with battery terminals.........there are also recommendations about using a strip of metal foil to take up any slack in a holder; personally I would not use it unless in dire emergency as you do need to make sure foil cannot slip and come into contact with both connections at once.