Technical Daytime running lights and rear cluster

[mattbacon]

I just thought I'd post this here in case anyone else experiences the same issue. For a couple of years, we've had a "Check daytime running lights" alert coming on at start-up, and one light failed on the offside front. I've changed the bulb a couple of times to no good effect. Goodness knows how it's got through the MOT, but maybe DRLs aren't mandatory on a '13 car. Recently the top bulb in the rear nearside cluster also failed. No spares, so I popped out the DRL bulb, looked in the rear cluster and thought they were the same, and trundled off to Halfords with the old bulb in my pocket. Matched it to a single filament 21W bulb and bought a pair. Put them in and still no luck. THEN I had the bright idea of looking at the bulbs in the units that WERE working. Both of them are dual filament 21W/5W bulbs. So off I went again to get proper replacements (looks like whoever changed the front one before I changed it first a couple of years back had ALSO put the wrong type in. The rear replacement worked straight away, but the front still didn't. I jiggled it and it flickered so I tried taking it out, rotating it 180 degrees and putting it back in. BINGO! That one now works, too. So the moral of this story is: first, don't just take the dead bulb when you buy a replacement, look at the one that's still working; secondly even if there's no apparent need for a twin-filament bulb, it might be one; and finally although it shouldn't be possible to fit a single filament bulb in a twin filament socket, or a twin filament bulb the wrong way round, in FIAT sockets you can do both...

The front daytime running light and top bulb in the rear cluster are both dual filament 21W/5W bulbs.

best,
M.

 

[Panda IIs]

I just thought I'd post this here in case anyone else experiences the same issue. For a couple of years, we've had a "Check daytime running lights" alert coming on at start-up, and one light failed on the offside front. I've changed the bulb a couple of times to no good effect. Goodness knows how it's got through the MOT, but maybe DRLs aren't mandatory on a '13 car. Recently the top bulb in the rear nearside cluster also failed. No spares, so I popped out the DRL bulb, looked in the rear cluster and thought they were the same, and trundled off to Halfords with the old bulb in my pocket. Matched it to a single filament 21W bulb and bought a pair. Put them in and still no luck. THEN I had the bright idea of looking at the bulbs in the units that WERE working. Both of them are dual filament 21W/5W bulbs. So off I went again to get proper replacements (looks like whoever changed the front one before I changed it first a couple of years back had ALSO put the wrong type in. The rear replacement worked straight away, but the front still didn't. I jiggled it and it flickered so I tried taking it out, rotating it 180 degrees and putting it back in. BINGO! That one now works, too. So the moral of this story is: first, don't just take the dead bulb when you buy a replacement, look at the one that's still working; secondly even if there's no apparent need for a twin-filament bulb, it might be one; and finally although it shouldn't be possible to fit a single filament bulb in a twin filament socket, or a twin filament bulb the wrong way round, in FIAT sockets you can do both...

The front daytime running light and top bulb in the rear cluster are both dual filament 21W/5W bulbs.

best,
M.

Yep twin filaments all round and you will note the DRLs only have a two wire connection so use some CanBus magic to dim when headlights are switched on. Also the rear clusters only use one filament for the rear marker light in one of the locations (from memory).

Thanks for the post though! Also I think the DRL sockets have "previous" in that they seem to get hot and melt contacts (sometimes).

 

[chris3234]

I just thought I'd post this here in case anyone else experiences the same issue. For a couple of years, we've had a "Check daytime running lights" alert coming on at start-up, and one light failed on the offside front. I've changed the bulb a couple of times to no good effect. Goodness knows how it's got through the MOT, but maybe DRLs aren't mandatory on a '13 car. Recently the top bulb in the rear nearside cluster also failed. No spares, so I popped out the DRL bulb, looked in the rear cluster and thought they were the same, and trundled off to Halfords with the old bulb in my pocket. Matched it to a single filament 21W bulb and bought a pair. Put them in and still no luck. THEN I had the bright idea of looking at the bulbs in the units that WERE working. Both of them are dual filament 21W/5W bulbs. So off I went again to get proper replacements (looks like whoever changed the front one before I changed it first a couple of years back had ALSO put the wrong type in. The rear replacement worked straight away, but the front still didn't. I jiggled it and it flickered so I tried taking it out, rotating it 180 degrees and putting it back in. BINGO! That one now works, too. So the moral of this story is: first, don't just take the dead bulb when you buy a replacement, look at the one that's still working; secondly even if there's no apparent need for a twin-filament bulb, it might be one; and finally although it shouldn't be possible to fit a single filament bulb in a twin filament socket, or a twin filament bulb the wrong way round, in FIAT sockets you can do both...

The front daytime running light and top bulb in the rear cluster are both dual filament 21W/5W bulbs.

best,
M.

There is a need for the duel filiments

The 21w is the drl light
And the 5 w is used when you have dipped beam on then the 21w is turned off

 

[chris3234]

Yep twin filaments all round and you will note the DRLs only have a two wire connection so use some CanBus magic to dim when headlights are switched on. Also the rear clusters only use one filament for the rear marker light in one of the locations (from memory).

Thanks for the post though! Also I think the DRL sockets have "previous" in that they seem to get hot and melt contacts (sometimes).

Why would it need more then 2 wires?

Each is a live feed for each filiment

The earth is provided by the bulb holder no doubt

 

[Herts Hillhopper]

Why would it need more then 2 wires?

Each is a live feed for each filiment

The earth is provided by the bulb holder no doubt

No - all plastic housing. This was covered in another post. One of the wires is the earth, and the other appears to connect to both filaments. I think the Canbus ‘pulses’ the power when it needs the dimmer (sidelight) - just enough to light the thinner filament but not the thicker. It may well be that actually both filaments are ‘on’ for the DRL. (Take the bulb holder out and the light remains on, so one of the wires has to be earth).

 

[Herts Hillhopper]

... I jiggled it and it flickered so I tried taking it out, rotating it 180 degrees and putting it back in. BINGO! That one now works, too…

Wherever a twin filament 21/5w bulb is used (on any car) the bayonet pins are offset, so it should only fit one way round. If you really force it in they can be made to fit the other way… but instead, if you find it’s tight, flip it180 degrees and it will fit easily.

 

[chris3234]

No - all plastic housing. This was covered in another post. One of the wires is the earth, and the other appears to connect to both filaments. I think the Canbus ‘pulses’ the power when it needs the dimmer (sidelight) - just enough to light the thinner filament but not the thicker. It may well be that actually both filaments are ‘on’ for the DRL. (Take the bulb holder out and the light remains on, so one of the wires has to be earth).

The bulb holder is plastic?

 

[Herts Hillhopper]

The bulb holder is plastic?

Yes

It’s as if the return path is via the second filament.

 

[Panda IIs]

Why would it need more then 2 wires?

Each is a live feed for each filiment

The earth is provided by the bulb holder no doubt

What he (@Herts Hillhopper ) said! That's why I mentioned the CanBus witchcraft.

 

[Panda IIs]

The bulb holder is plastic?

Which is why any heat (high resistance) at the contacts can cause an issue.