General DRL/Fog Light issue

[Ravenskull]

Have just replaced the DRL bulbs in my 500L; previous owner had fitted non canbus compatible LEDs, and after two weeks I was getting sick of the error messages.

However, my left DRL doesn't light up - instead the left fog light comes on, and I'm still getting the "check DRL bulbs" message on the dash. Right hand side operates normally.

Replacements were standard Bosch bulbs; both are in working order (both bulbs function tested in the side that was working normally).

As a short would result in both fog & DRL illuminated (and presumably no error messages), I don't *think* this is a wiring fault(?).

Does anyone have any ideas?

 

[The Panda Nut]

Bulb holders plugged into the wrong lights? If they fit??

 

[Ravenskull]

Bulb holders plugged into the wrong lights? If they fit??

It's definitely not that - despite the DRL filament not lighting up, the sidelight filament works fine (twin filament bulb).
I did wonder if the wires are crossed somewhere further up in the circuit though - Unfortunately i haven't tracked down a wiring diagram yet to figure it out.

 

[The Panda Nut]

I hot wire the light units etc to test they actually work as this rules that out before starting on checking wires. I.e. wire live and earth direct from the battery.
I dont trust moden bulb holders, Ive had a few play up over the years. Next thing to check is the earth wires. If earths are bad, the power will find its way wherever it can, Sometimes back down another live causing the wrong thing to work. ID the DRL earth wire and check by wiring direct from the lamp to earth at the battery and see if this gets the right light to work. If it does then your down 1 problem. If not you need to also check the lives.
Sometimes disturbing wires makes the earth work and sometimes it stops it. If you have a volt meter you can check that you have live feeds to the lamp unit for both DRL and fog when its turned on. Obviously check the fuses. I am a great believer in checking the whole lot as I dont trust the schematics to be 100% accurate, Could be that the light its self is damaged or the bulb holder. Some bulbs now come complete with a new holder which is telling. Can you hold the holder in tight and get someone to check if it has an effect?

Check connections at light units and harness joins on both sides in case one side feeds the other.
I use a needle to test wires and to apply power to different sections.

Arduous and time consuming. I hope it is a simple earthing issue and you find this quickly. Its mouch mmore likely something simple than an ECU issue.

Good luck

 

[varesecrazy]

Have just replaced the DRL bulbs in my 500L; previous owner had fitted non canbus compatible LEDs, and after two weeks I was getting sick of the error messages.

However, my left DRL doesn't light up - instead the left fog light comes on, and I'm still getting the "check DRL bulbs" message on the dash. Right hand side operates normally.

Replacements were standard Bosch bulbs; both are in working order (both bulbs function tested in the side that was working normally).

As a short would result in both fog & DRL illuminated (and presumably no error messages), I don't *think* this is a wiring fault(?).

Does anyone have any ideas?

Appreciating you've not had it long... ,

What Actually worked before..?

DRL bulb holders have a hard life, get HOT and often distort/melt

Have you swapped Left For Right?

My punto blew a DRL bulb after 42,000 Illuminated miles, holder was crispy..

But still working now @75k, other bulb is still 2012 factory fit

The 2 door 500's have similar /worse apparently

 

[Ravenskull]

Appreciating you've not had it long... ,

What Actually worked before..?

DRL bulb holders have a hard life, get HOT and often distort/melt

Have you swapped Left For Right?

My punto blew a DRL bulb after 42,000 Illuminated miles, holder was crispy..

But still working now @75k, other bulb is still 2012 factory fit

The 2 door 500's have similar /worse apparently

Hard to tell what was working before; previous owner had added LEDs to sidelights/DRL fittings, and HIDs (without canbus modules) to headlight & fog fittings. So nothing worked properly - turn the lights on, and they would illuminated, trigger an error, and go out again - this wasn't consistent either, so obviously the ECU wasn't happy about the situation.

On the plus side, although the DRL is still not working, the fog light appears to have cured itself; I suspect that it may have been a result of the ECU not liking the HIDs the last owner added.