Facelift W163 Alarm Problem

[E55BOF]

Good evening Gentlemen. I have an alarm problem with my 2001 ML500; it goes off randomly at night. It might perhaps be connected with the old battery, which was rather tired; it would start the car without difficulty when recently charged, but after standing for a few days, after one cold night it was pretty flat.

I've just fitted a new battery, which I'm hoping will cure the problem, and I can lock the car on the key without arming the alarm, but I've noticed something odd. When I unlock the car with the remote, I get the single flash of the indicators, but when I lock it the same way, the alarm arms and the red telltale blinks, but there is no indicator flash at all. My iCarsoft MB II detects no fault codes in either OBD or Benz mode.

Does anybody know, could a previous owner have programmed it this way, or does it indicate a fault?

 

[Smart320]

I would guess it's the alarm unit that is failing, think it has a battery inside, you need to renew the unit if that's the case.

 

[BIG UN]

I would say faulty alarm module. Swapped one on a w209 that kept flattening the battery. The alarm is the control module as well, after swapping the CLK it hasn't flattened the battery since & it now has an audible tone when you lock the car!!

Sent from my SM-G960F using Tapatalk

 

[Codger49]

I believe the audible tone can be switched on or off via Star.

In the past, alarm modules had the tone defaulted to off, whereas more recent modules seem to be defaulted to on. I personally prefer the tone on, its quite a discreet sound.

 

[Joderest]

I had this exact issue with my W163 (ML270) 1 flash on disarm, no flash at all on arm and lock. However, the alarm did not go off, but sometimes the indicators were flashing like it had gone off.
I replaced the alarm unit with a chance 2nd hand unit off e bay (only paid £15 so thought worth a chance) its worked perfectly ever since. What happens is the batteries in the unit degrade, they then leak their contents onto the circuit board and ruin the alarm.
Its located under the wipers with requires the scuttle and bits to be removed, ball ache of a job. I extended the wiring out into the engine bay and made a bracket for the alarm, i also inverted it so any gunk running out of batteries goes out the alarm, not onto the circuit board.
Well, thats my story anyway.

 

[E55BOF]

Fitted the new battery, and the alarm didn't go off last night. I'm keeping the key fob very handy, and will see how it goes.

The alarm, and what the car does on locking and unlocking, can definitely be programmed. The ML320 unlocks all locks first press of the remote; the ML500 unlocks only the driver's door. The 320 fog and side lights come on when the car is unlocked; the 500's don't. The 320 gives three flashes of the indicators, and three chirps, when the car is locked with the remote; the 500 does not. Both give one chirp, and one flash, when the car is opened with the remote. They're both facelift W163s.

I know of the common battery fault with MB alarm units of that era, and there may of course be a fault with the alarm, but even if so, I'm sure there's more to it than that. I'm selling the 320, and I can live with what the 500 does, so long as the alarm doesn't go off when it shouldn't. Keeping a watching brief, a.k.a. masterly inaction, would seem the best course for now...

 

[E55BOF]

The alarm's still going off, so new unit time.

 

[Steven Stoole]

I Have the same car w163 ML500. Love this beast. When i unlock mine one flash and drivers door unlocks as well as main lights and fog lights lite up. I do believe the reason the lights lite up when opening is due to the auto funtion being enabled on your car. This is via the stalk on the left. i will try it tonight when it is dark to turn this off. If i then push reomote to open again it will then open the rest of the doors.
Hope this helps and im going to check my alarm system as well for battery leakage.

 

[E55BOF]

Replaced the alarm siren - awkward to get at; removing the bonnet would make access for dismantling much easier, but I'm working alone out of doors, so that's not an option - and it's now quiet at night again. Ah.....

I get one blink and one chirp on unlocking the car, as before, but still nothing on locking it. I'll get to the bottom of it eventually.

Yes, the lights Auto position does also enable the sidelights and front fogs delay function on switching off, but about a week ago mine were still on an hour later, so I now turn it off. That, too, I'll get to the bottom of eventually...

 

[Joderest]

It may help.
Yesterday, the alarm on my W163 went off, first time ever, no reason i could find. I unlocked it to stop alarm, but when i locked it again i had lost the three flashes to confirm locked. I disconnected the alarm and checked the connections were clean ( did i mention i moved it out from under the scuttle to engine compartment, made life a lot easier) when i reconnected it the three flashes came back.
I put my MB2 scanner on the car and went into the AAM, found the alarm bit and there was a stored code which i deleted.
It all works fine now. I wonder if you have stored codes that need deleting ?