Permanent headlights

[idlerider]

I was surprised to notice that my automatic headlights were on although it was bright sunlight today. Further investigation showed that the light switch has no effect, athough the dip/main beam stalk works OK. Nothing, it seems, will induce the headlights to turn off other than switching off the engine and removing the key. Can anyone help/advise, please?

 

[LostKiwi]

I had this in my R class.

Has your car ever had the windscreen replaced?

Do you have automatic wipers? If so how they behave in light rain?

On mine I had your exact symptoms plus auto wipers would occasionally do a single wipe, then 2 or 3 wipers on speed 1 then go into full manic mode high speed.

Turns out the windscreen had been replaced and the sensor not recalibrated using Star. Recalibrated and all good.

 

[EmilysDad]

My (preface lift) 07 plate R Class had the option in the dash cluster to have the lights always on or on & off via the switch ..... I forget now exactly how it was described in the dash cluster, manual & something

 

[EmilysDad]

......

On mine I had your exact symptoms plus auto wipers would occasionally do a single wipe, then 2 or 3 wipers on speed 1 then go into full manic mode high speed.

Turns out the windscreen had been replaced and the sensor not recalibrated using Star. Recalibrated and all good.

The wipers on my R Class used to go to full monsoon mode when in auto, but it was the sensor that wasn't clipped to the screen properly.

 

[idlerider]

I had this in my R class.

Has your car ever had the windscreen replaced?

Do you have automatic wipers? If so how they behave in light rain?

On mine I had your exact symptoms plus auto wipers would occasionally do a single wipe, then 2 or 3 wipers on speed 1 then go into full manic mode high speed.

Turns out the windscreen had been replaced and the sensor not recalibrated using Star. Recalibrated and all good.

Your response makes good sense - but the lights have worked faultlessly for the last couple of years. Yes, occasionally the wipers go mad but I had the same thing happen regularly on a Saab Aero. I'll get the Merc dealer to check it - and thanks!

 

[LostKiwi]

If you have the option to turn off DRLs you'll gain control of your headlights.

With DRLs enabled the headlights will default to auto (even with switch set to off).
With DRLs disabled the headlights behave as per how you'd expect (though auto may turn on when light levels aren't low).

 

[mioba]

Beat me to it LK

 

[idlerider]

If you have the option to turn off DRLs you'll gain control of your headlights.

With DRLs enabled the headlights will default to auto (even with switch set to off).
With DRLs disabled the headlights behave as per how you'd expect (though auto may turn on when light levels aren't low).

Great, LK! - now tell me what 'DRLs' are.

 

[Blobcat]

Daytime Running Lights

 

[idlerider]

Daytime Running Lights

Mine doesn't have those. Computer just gives option of headlights as 'auto' or 'permanent.' And I've tried all the combinations, with no success.

 

[sausage]

Page 6 might be worth a read:
https://forums.mercedesclub.org.uk/...ading-like-a-cancer-help-please.191622/page-6

"So just a quick update from Prestige, apparently the headlights should come on if the Canbus fails, it's a safety feature so that you're not left without headlights if it's dark. They disconnected the Canbus from the passenger side SAM and sure enough the headlight comes on and when they turned the headlights off the nearside headlight stays on, as it should with no Canbus signal."

 

[idlerider]

Page 6 might be worth a read:
https://forums.mercedesclub.org.uk/...ading-like-a-cancer-help-please.191622/page-6

"So just a quick update from Prestige, apparently the headlights should come on if the Canbus fails, it's a safety feature so that you're not left without headlights if it's dark. They disconnected the Canbus from the passenger side SAM and sure enough the headlight comes on and when they turned the headlights off the nearside headlight stays on, as it should with no Canbus signal."

Can you tell me which canbus is likely to be faulty and where it's located? (And what's a 'SAM'?)

 

[LostKiwi]

Canbus runs right through the car. It's a network connecting control modules together.
It's a barsteward to fault find.

The SAMs are Signal Acquisition Modules. There may be one or more dotted around the car. Smarts have one, an R230 has three.

A good scanner should show if there are canbus related issues or SAM issues.

 

[idlerider]

Thanks, everyone, for all your advice - I'll fire up my OBD reader tomorrow.

 

[idlerider]

UPDATE: checked this morning - no change - light switch still inoperative and permanent headlights. Plugged in my OBD scanner - no codes. Switched off, removed OBD plug, restarted - HURRAH! - fault disappeared, lights working as normal. Why? - who knows? - but no complaints here.

 

[LostKiwi]

UPDATE: checked this morning - no change - light switch still inoperative and permanent headlights. Plugged in my OBD scanner - no codes. Switched off, removed OBD plug, restarted - HURRAH! - fault disappeared, lights working as normal. Why? - who knows? - but no complaints here.

What OBD scanner are you using?

 

[idlerider]

What OBD scanner are you using?

"Streetwize" - cheap as chips - seems to work OK though.

 

[LostKiwi]

Ok there's why you're not seeing any errors.
That will be a generic code reader and as such will only scan a small subset of codes for the engine ECU.
It won't scan SAMs, airbags, transmission bor a whole host of other control units.

You need to get it scanned on a MB compatible scanner such as made by Autel, iCarsoft or a host of other manufacturers.
The best scan is on STAR/Xentry which is the dealer level diagnostic.

 

[sausage]

Can you tell me which canbus is likely to be faulty and where it's located? (And what's a 'SAM'?)

Sorry, I really do not have that level of knowledge and you probably now know a lot more about the canbus and SAMS than I do. I posted the reference to the other thread because I thought there was a similarity that might help you. Good luck, I hope you get to the bottom of it all.

 

[SL350 in Canada]

Hello From Canada
MY SL350 is from Japan. But the car is Left-hand drive. Same as Europe.
Question one there is a slider bar on the top of the light to flatten the beam so as not to blind the oncoming drivers.

Question two MY VIN is WDB2304671F112654 Can the star system turn DRL for use in Canada?
Can the Japanese command be reverted back to English? Thanking one and all for your advice.

Thanks Stephne