Viano alarm siren location and repair/replace

[Droverunner]

Did a forum search and see M80 was looking for his missing alarm siren on his Viano but no more info as to its certain location. I'm going to change mine or fit new batteries as a start towards sorting the couple of locking/alarm glitches I'm seeing.

Anyone know for certain where the siren unit is on a Viano around 2012 (or Vito I guess)... and anyone split the unit to see if replacing batteries works?

 

[mioba]

Best bet, go to the dealers and get an alalrm siren. ask then to print off or tell you where its located. They will have the page open for thier IPL anyhow. They are usually helpful with things like this when you are buying from them.

A few google searches suggestes the siren is in the N/S wheel arch behind the lining.

They usually on a metal bracket, one wire to unplug and one bolt to remove the siren (5 mins).

Most time consuming part is getting the van up, wheel off, lining out (not 5 mins).

 

[M80]

O/s fr wing.
It looks similar to a horn but more complicated.

They are sealed and about £155. Only 3 wires to them. So to my mind that is +ve & -ve for charging, and the siren trigger.
That would mean all other monitoring is taken care of at another electronic unit, but haven't got round to researching that yet.

If I'm lucky when I do find it it might be unplugged to disguise whatever they removed the siren for.

 

[Droverunner]

Thanks... do you think that is behind bumper or to rear of wheel?

 

[joderest]

from past experience with my old W163, what causes the alarm to break down is the acid leaking out of the old batteries located inside, this runs on to the circuit board and makes any repair impossible, new unit or decent 2nd hand one is way forward.
On the W163 it was located under the front scuttle, meaning about an hours dismantling to get at it as wipers had to be removed as well as the linkage and motor.
I cut and extended the wires out of that location into the engine compartment, and purchased a 2nd hand unit for £15, took a chance. That was three years ago, its still there and working, but would now be a 5 min job to replace as very assessable. I also installed it upside down, so any acid from the batteries runs out of the unit, not on the circuit board.

 

[curious]

If I'm lucky when I do find it it might be unplugged to disguise whatever they removed the siren for.

If it's anything like the siren I had in my W203 (and it sounds like it might be) it started to cause random lights flashing and strange noises when parked up. It's a sealed unit and the battery had given up. Cutting them open and seeing if you can DIY anything inside was a waste of time.
I felt the replacement cost wasn't worthwhile and simply left it unplugged to remove the problematic symptoms.
(Comes up on Star as open circuit but nothing else.)

 

[M80]

Thanks... do you think that is behind bumper or to rear of wheel?

The unit comes with a U bracket, to bolt it to the front cross member I expect.
My cross member isn't on, but I would look inside the wheel liner at the very front.

 

[Droverunner]

Found it now... behind the wheelarch liner in front of the driver's side front wheel. Attached to a plastic bracket that attaches the lower face of the bumper to the chassis leg that sticks out forwards beside the radiator.

Alarm siren looks clean... unplugging its three wire connector made to difference to the blinking sidelights after plip locking. I can confirm the siren either isn't working or isn't being triggered because I jacked it up while locked and the hazard lights flashed but no noise.

 

[M80]

Another simple test is lock as normal, and then unlock the door with the blade. That should trigger the alarm.

I think my new unit is faulty. I removed it and while i would expect to be able to read an output voltage on the pins there's nowt.

 

[Droverunner]

I'll try that test too thanks.

 

[M80]

A little more that might be of use to someone in future.

The 211 started flashing the indicators when locked.
Some testing and I concluded the siren was u/s.

A new one arrived this am, there is no voltage across any of the 3 pins. It makes sense that there is a blocking diode so it can't be drained down if the main battery is flat.

New siren in and all works on the 211.

Both outer pins show 12v to the mid pin on the 211.
Only one pin is 12v to mid pin on the 639.
I'm trying to source drawing/s to find where my other line is lost. I've read that the o/h light unit is a connection point, but nowt obvious there.

 

[M80]

A bit more, much later info.

At the alarm siren there are 3 wires, as said.
They being 'red +ve 12 volts', 'brown -ve' (both for charging imo.
The 3rd 'red / green has continuity up to the o/h light unit'. When the alarm is triggered this becomes +ve (I measure 10.4 volts , but believe it to be essentially a 12volt trigger brought down by low main battery voltage and volt drop along small csa wiring).
This makes the o/h light the alarm control unit. As the 638 had a separate alarm control, as do some other MB's, this would make sense.

The siren isn't sealed, with the 2 squared bolts removed there is access to 2 Philips screws. Undo those the siren can be split.
The battery within is 7.2volts, 250ma nimh. Easily replaceable

Vito/Viano Siren Battery for Mercedes Van Alarm Security 250mAh Car Backup | eBay

Compatible with Vito(2003~) & Viano(2004~) siren module. Consisting of 6 NIMH batteries in formation to 7.2V, 250mAh. Suitable for a 5 year back up duration. Type: Ni-MH Battery.

www.ebay.co.uk

I believe my new siren to be faulty, the battery seems to hold charge when bench charged.
The trouble with the MB warranty style is that if I return it and they decide it isn't that, I would be paying their extortionate diagnostic charge. And they may require the van for that also. I'm not going to chance that.

I'm looking out for a 2nd hand unit to, hopefully, use my good battery on.
My Viano had its siren removed so I can't repair the original and the electronics within the brand new one are beyond me.

It continues to flash until locked twice. Not a biggy really.

 

[Droverunner]

It's interesting I had just the same fault of the double plip needed plus one night a possible false triggering of the siren. But a year on from posting this thread now my Viano is in daily use after standing for months before I bought it (and the main battery was replaced early on) I've not seen the problem since.

I think you'll know a used unit will be a gamble as the internal battery is known to leak into the board and make a right mess.

 

[M80]

I think you'll know a used unit will be a gamble as the internal battery is known to leak into the board and make a right mess.

True enough, but if from eBay it gets returned.

Last week I finally diagnosed my rear wiper fault was definitely the SAM. Knowing how temperamental these units are the chances of a good one from a breaker, even with "fully tested" bs it is a gamble.
Anyway it seems good so far, and with a testing period of 27 days remaining I'm hopeful it doesn't need to go back.

I'm happy to have the old one, with known minor issue, for future testing.

 

[MinionBob]

Thought I would just add to this thread rather than start afresh as it has valuable content.

I have had x2 consecutive false alarms on my 2012 Viano in the last 24hrs - both around 22:30.

1) Is there anyway to know what has triggered the alarm?
2) Are false alarms a symptom of failing backup battery?

 

[Blobcat]

Thought I would just add to this thread rather than start afresh as it has valuable content.

I have had x2 consecutive false alarms on my 2012 Viano in the last 24hrs - both around 22:30.

1) Is there anyway to know what has triggered the alarm?
2) Are false alarms a symptom of failing backup battery?

Moths or other flying insects can be the culprit. Turn the interior motion sensor off tonight and see if that makes a difference

 

[Droverunner]

First thing is to reassure yourself these are actually false alarms and not an attempt at interference or as above a moth inside. It's also my belief extreme heat can trigger false alarms.

Next thing to check for is low main battery voltage. When I bought my Viano a year ago the main battery would start it fine but was down on voltage causing some issues inc the alarm faulting. Finally it could be the alarm unit itself needs replacing as at ten years old there's every chance its internal battery is leaking over the electronics.

 

[M80]

I've mentioned somewhere, it may be in this thread.
The Viano alarm unit, a bitch to remove, but easy to strip, inspect the circuit board, and replace the battery.

Alarm siren unit in hand,
remove the nut / bolts from the unit, hidden by those are 2 Philips screws.
Those removed the board is easy to see.
The battery cell is held by a rubber band and easily unplugs.
Approx £25 on eBay for the cell.

 

[MinionBob]

A bug does seem to be the culprit as both times it 22:30-ish, which seems a little odd as it has the opportunity to go off anytime it wants. Ill disable the internal motion sensor and see. Just have to work out which of the 543 buttons it is!

 

[Blobcat]

A bug does seem to be the culprit as both times it 22:30-ish, which seems a little odd as it has the opportunity to go off anytime it wants. Ill disable the internal motion sensor and see. Just have to work out which of the 543 buttons it is!

The one that looks like microwave radiation coming down from the roof of the vehicle