S320l- w220 -m112-Bonnet Sensor

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S320L

New Member
Joined
Dec 17, 2015
Messages
19
Car
S320L W220
Hi all,

In the the speedo unit a system warning came up, saying that the bonnet was open. But its not, had it checked and they said it was the bonnet sensor. Got an other one and fitted, but the error still comes up.

The sensor i changed was one of the front catches that has the micro switch.

Do i have to get the error cleared with a diagnostic tool ?
or it there an other one ?
or anything else it could be ?
:dk:

John
 
Last edited:
I checked the micro switches on both the old and new one and they are working ok

Anyone ?

:dk:
 
Forgot to add, it keeps setting off the alarm. If that helps
 
If someone forces open the bonnet, that switch will trigger the alarm.
It could be that the alarm siren is corrupt and is giving a false warning that the bonnet is open.

If your alarm siren is the original factory fitted unit then it is about 10 years old, the all eventually give trouble at that age.

Best to unplug the alarm siren to see if that solves the bonnet open issue.
Unplug the alarm siren only when the car is unlocked with the remote, otherwise it may go off.

Dec
 
Stopped the alarm from being triggered. .

I cut the connector off the end of the old sensor and connected the two wires.

As per photo.

Still got the bonnet open warning :wallbash:
 

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How did you stop the alarm from being triggered?

Dec
 
^

by connecting the brown and grey wire together as per photo above.
 
My theory is that the alarm siren PCB is damage, because of this, the alarm thinks the bonnet is open and that is in some way causing the false report of the bonnet being open.

Unplugging the alarm siren might cure the fault, if not then it may need to be turned of in diagnostic.
Pulling the alarm fuse out, as far as I know, wont kill the alarm, only unplugging it will isolate it for sure.

See... https://www.google.ie/search?q=w220...&biw=1217&bih=856&dpr=1#imgrc=Q3EkkdhIlyYpjM:

Dec
 
thanks for that,

need to be after xmas now, as im away,

will keep you updated

:thumb:
 
You will need to put the bonnet switch back the way it should be, because that switch has two functions, to trigger the alarm and to warn if bonnet is open.

Maybe the bonnet open warning does need to be turned of in diagnostics or the alarm siren is causing the fault.

Dec
 

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