ML320 (W163)
 

Hi,
Can anyone tell me where is & how to get to the alarm unit on a 163 ML320.
I steamed cleaned the engine so I dis-connected the battery, the alarm just made a clicking noise which to me means that the back-up battery within the unit is faulty. I had the same problem on a BMW once. When the battery was re-connected the alarm sounded normally.
Many Thanks.

Don't know what you mean by 'alarm unit', but there is no back-up battery. The alarm system is a simple horn mounted on the firewall with a single wire, and powered by the AAM.

Alarm ML320 163
 

Hi,
Thank You for your reply, if there is no alarm back up battery then what would make the alarm sound when the battery is dis-connected or say a thief cuts the wires. There must be another power source because my alarm started to click as soon as the battery was dis-connected and then sounded off as normal the moment the battery was re-connected. I had the same problem once before on a BMW, i located a alarm unit ( black box ) changed the battery which was a number of large penny batteries and all was well.
Thanking anyone in advance for any infomation.
Looking at the picture above, my ML does not have any horn showing on the firewall, the alarm sound / clicking is coming from within the area between firewall and cab.

Again, the ML does not have a back-up power source for its alarm system. You have an aftermarket alarm installed in your vehicle (which you are unaware of) which uses a back-up power source.

I can only assume that you recently bought the truck and are now finding this problem. The alarm system is wired through the overhead trip computer and when they go bad people do not want to replace it and their remedy is to install an aftermarket alarm.

Actually Maj. D I think it does. The European, or at least some countries in Europe, W163 ML's have a completely different OEM alarm system than the Horn in the North American models.

Paypal10, I think you do have a factory alarm system. A European member of another W163 forum said the alarm is mounted behind the right front wheel well liner.
This is why Year, Model and LOCATION is very important in your profile when asking for assistance.
Where are you Located?????
The alarm is #20 in the EPC diagram.
Mike

Thank you, point taken about location - England - never used one of these sites before. I will be looking behind the wheel well. I feel the clicking is a relay that is not getting enough power i.e. from the alarm battery when the main battery is dis-connected. My model does not have a trip computer. It is factory alarm that under normal use works perfectly. Thanks again.

Mike and PayPal, now I get the picture.