"Hood Open" message even when micro switch is OK

[Hankiss]

Hello, greetings to all members. Recently (with no reason) in my 2010 W221 “Opened Hood” message comes and beebs. I checked micro switch in the latch. Disconnected it from the loop and tested with multimeter. It clicks and works OK. I even short wired the connector (behind the lamp) to bypass the switch. Still shows the message and beebs. I couldn’t find wire diagram for the switch. I tried to disable the warning message using Star Diagnosis but could not see the function there. Can someone here help, please? I am stuck with beebing S-class.

 

[A.J.]

Sorry if this sounds a bit simple, you have most likely already tried this but I sometimes get the same problem after checking levels under the bonnet. Have you tried re-closing the bonnet a bit firmer than you did previously ?

 

[mioba]

Is there a pad or something that pushes on the switch - perhaps worn down thus creating a gap.

 

[KennyN]

How many switches ?

On the BMW there are two catches , and two switches.

K

 

[Hankiss]

Hi, thank you all above for their suggestions. I don’t think this is switch mechanical fault. I read somewhere, that signal from the micro switch goes to rear SAM (in a trunk). In my s-class the rear SAM is located behind rear seat. I checked electrical diagram for rear SAM in WIS but there is nothing relating to hood micro switch. I am pretty sure the micro-switch is OK, because when I short wired it there was the same problem. My wipers also don’t work and think this is related to hood problem. I can’t find diagram for the switch (where it connects to…). Anyone has access to this diagram, please ? Cheers

 

[A.J.]

Hi, thank you all above for their suggestions. I don’t think this is switch mechanical fault. I read somewhere, that signal from the micro switch goes to rear SAM (in a trunk). In my s-class the rear SAM is located behind rear seat. I checked electrical diagram for rear SAM in WIS but there is nothing relating to hood micro switch. I am pretty sure the micro-switch is OK, because when I short wired it there was the same problem. My wipers also don’t work and think this is related to hood problem. I can’t find diagram for the switch (where it connects to…). Anyone has access to this diagram, please ? Cheers

I would imagine that the wipers don't work because the car thinks the hood is not closed properly. Sorry no wiring diagram

 

[Hankiss]

Definitely the micro switch is OK. I need to check the wire from switch to rear SAM but can’t do it without diagram. Or reliable info where the wires go to? Saddly, I’ve a filling that this Forum will not help me much.

 

[KennyN]

Have you had a look through this , providing it is the same as yours.

Fuses chart for 2008 s550 please!! - MBWorld.org Forums

S-Class (W221) - Fuses chart for 2008 s550 please!! - Hello, anyone happen to have the fuses chart for 2008 S550? I could not find it it my car anywhere including the back where the tool box is :(. I called the dealer try to buy one, they don't have it. Could someone please share a copy, thanks...

mbworld.org

Wires 910 / 911 seem to be for the bonnet switch and you can see where it connects to the rear of the SAM , may make tracing the cables easier.

K

 

[Headhurts]

Sorry if this sounds a bit simple, you have most likely already tried this but I sometimes get the same problem after checking levels under the bonnet. Have you tried re-closing the bonnet a bit firmer than you did previously ?

Have you tried A.J suggestion?

I have had 3 E class Mercedes and although the bonnet is closed and secure they displayed the bonnet insecure notification, they needed a really good slam shut to not display bonnet insecure.

I realise your car is a different model but it’s worth a try, my current GLC does not require force.

Robin

 

[SL63 Mark]

I am pretty sure the micro-switch is OK, because when I short wired it there was the same problem.

The thing is, it's not as simple as shorting out the micro switches. You need exactly the same value of resistance or whatever. It is so clever you can't fool them anymore. If the switch is not returning exactly the correct value the car will throw an error message.

 

[Hankiss]

Have you had a look through this , providing it is the same as yours.

Fuses chart for 2008 s550 please!! - MBWorld.org Forums

S-Class (W221) - Fuses chart for 2008 s550 please!! - Hello, anyone happen to have the fuses chart for 2008 S550? I could not find it it my car anywhere including the back where the tool box is :(. I called the dealer try to buy one, they don't have it. Could someone please share a copy, thanks...

mbworld.org

Wires 910 / 911 seem to be for the bonnet switch and you can see where it connects to the rear of the SAM , may make tracing the cables easier.

K

 

[Hankiss]

Thanks for the info. I can't see wires 910 and 911. I don't hadiagram. Rear SAM is located behind rear seat. Very difficult access to the box.

 

[Hankiss]

Hi again, I tried to disable the hood switch usinh DAS. But I can find the option. Any advice on that matter, please?

 

[Hankiss]

Finally, I can report that I've identified the issue. Strangely, the old linkage was interfering with the latch mechanism, causing it to retract. This prevented the latch from fully engaging with the small metal spring that presses on the micro switch. It took me a long time to uncover this unusual fault. While it is functional for the time being, I plan to replace the bonnet link in the near future. Thanks once again to all those who offered their assistance.

 

[Wighty]

Finally, I can report that I've identified the issue. Strangely, the old linkage was interfering with the latch mechanism, causing it to retract. This prevented the latch from fully engaging with the small metal spring that presses on the micro switch. It took me a long time to uncover this unusual fault. While it is functional for the time being, I plan to replace the bonnet link in the near future. Thanks once again to all those who offered their assistance.

Thanks for the update .

 

[ajlsl600]

Jesus! all that head scratching for a bonnet switch. Wot happened to drop and go. With hook if you foul up.
Progress... For WHO?
some time ago I worked out by accident that wipers don't work if bonnet not properly closed. The more sh1t that's linked up the more sh1t to go wrong
Why complicate life.

 

[rf065]

Jesus! all that head scratching for a bonnet switch. Wot happened to drop and go. With hook if you foul up.
Progress... For WHO?
some time ago I worked out by accident that wipers don't work if bonnet not properly closed. The more sh1t that's linked up the more sh1t to go wrong
Why complicate life.

To be fair with the wipers thing, they have to be below the bonnet line to prevent them spearing any pedestrians you may have inadvertantly run over. That's why you can no longer lift the wipers to change blades as the rear edge of the bonnet is in the way. So blame the pedestrian crash test results for that one.

 

[ajlsl600]

Yes I do, and should the pedestrian survive his arguing with my car, can I reasonably expect him to fund resetting bonnet hinges and anything else he wrecks
I miss my g and its grand "proper" bull bar, pedestrians generally made a point of avoiding contact with that.! I did clip a hippo rear end once on way back accross the farms to my house one night it's f amazing how a hippo can still try to tuck its arse in at last moment. Incident resolved following am by chaining bull bar Corner to fixed object and a bit of reversing work all sorted. No hardship, no codes no trip to benz and no further issues with hippo.

 

[EmilysDad]

...... That's why you can no longer lift the wipers to change blades as the rear edge of the bonnet is in the way. So blame the pedestrian crash test results for that one.

Though I can still change wipers with them in their proper park position, the rear edge of the bonnet wouldn't get in the way if the wipers were parked upright on the screen.

 

[Hankiss]

Hello, greeting to all Members,
This is just to close the case and provide some feedback. After a long, strenuous struggle with the "open bonnet" issue, I concluded that it wasn't the SAM, the bonnet micro switch, or the wiring... but the linkage. For some reason, the link (from the pull-out handle to the latch) was not fully retracked after the hood was closed. This prevented the little flat metal spring from being pushed against the micro switch. As a result, the micro switch sent a signal to the SAM "open hood." The solution is to replace the linkage. In my case, I managed to manipulate the link and resolve the problem. I hope this information will assist others experiencing a similar issue