Alarm going off when I attach battery R129

[Watchcame430]

Hi all,

Disconnected my battery the other day as not using car.

Went to connect it earlier and it sets the horn off!

Really getting tired of this now.

Any ideas? Done a Google but not found anything.

Thanks

 

[Dec]

Its normal for that year of car and depending on alarm fitted for the alarm to sound when you reattach the battery.

When the battery is reattached the alarm thinks it is being tampered with (or because the boot/bonnet or door is open) so it sounds off. If it happens in the future just unlock the car in the usually way, this will disarm the alarm.

Dec

 

[Watchcame430]

Its normal for that year of car and depending on alarm fitted for the alarm to sound when you reattach the battery.

When the battery is reattached the alarm thinks it is being tampered with (or because the boot/bonnet or door is open) so it sounds off. If it happens in the future just unlock the car in the usually way, this will disarm the alarm.

Dec

Thanks Dec ... I thought that might be the case and vaguely remember something similar happening like that before.


Issue is all doors were closed. Boot was open to attach the battery ... Attached it and it went off. Closed the boot ... Locked the doors ( horn going off all the time )
Unlocked , horn still going and started the engine ... Horn still going so had to disconnect the battery before my neighbours started moaning.


I must be missing something to reset the locks to stop it?

 

[Dec]

I used to have a 1994 W202 with a Scorpion alarm and it would sound off when the battery was reconnected and unlocking with the remote would disarm it.

It would seem you have a fault of some kind, any idea what alarm is fitted? The Red siren is a Scorpion siren, is yours like this, there are only 2 wires going into it.

Do you have an alarm remote or any type of odd looking keys with the car similar to the ones in the small picture inset in below picture?

Dec

 

[Watchcame430]

Mine is just the actual horn going off. I have the mercedes key fob 1994 in the middle.
I have never used the remote looking though ... Always opened with the key (central locking works though)

Could be a fault but I think it is to do with battery being disconnected and the doors being locked manually afterwards.

 

[Dec]

That explains a lot;
1… At some point your car was unlocked with the remote, this disarmed the alarm.

2…After the alarm was disarmed, the remote was never used again so you have had the alarm disarmed since the last time the remote was used to unlock the car. Unlocking/locking the car with the key blade in the door doesn’t disarm/arm the alarm, only the remote does that.
When you lock the car with the key in the door the hazards don't flash, when you lock the car with the remote the hazards do flash, 3 times or 2 times if the motion sensors are off via the slider switch on the remote.

3…When you reconnected the battery, the alarm automatically rearmed, it found the boot open so it sounded off, this is normal. What was missing was the remote control, had you had it to hand when you reconnected the battery then you would have been able to disarm the alarm by unlocking the car with the remote control.

Is there something wrong with the remote?

1. Lock/Unlock
2. Panic button turns on siren.
3. Battery indicator.
4. Round key to turn ON/OFF alarm.
5. Tactile switch under both buttons.
6. 12v Battery.
7. Don’t know what this screw dose it could be a distance or radio frequency adjuster, best left alone.
8. 3 pin socket for factory programming.
9. Slide switch;
In one position it turns OFF alarm internal motion sensors and indicators flashes 2 times.
In opposite position it turns ON alarm internal motion sensors and indicators flashes 3 times.

Operates on radio signal no infrared.

Dec

 

[Watchcame430]

Thanks for this ... Will have a look but the remote hasn't been used for over a year and taken the battery off loads of times. That's the confusing thing .. Not done anything different except the central locking mechanism in the boot was still making noise when I disconnected the battery.

The battery may be low ... Can't get to my charger but will get a brand new one this week.

 

[Dec]

That is confusing alright, when I had that alarm with that fob it was wired so as the only way to arm or disarm the alarm was with the remote or else you had to turn off the alarm with the round key.

I think yours is wired the same way mine was, in any case if the alarm was controlled by the door lock then you wouldn’t have been given a remote control, usually, if you didn’t have a remote control then the alarm was armed/disarmed at the door lock or rather when the vacuum pump ran.

What’s the current position with the alarm, I’m thinking the alarm might give up after a period of time and reset itself and that would explain what happened when you took the battery off several times.

Put a new battery in the remote and clean both battery contacts and the slide switch contacts, note how the slide switch falls out when you open the remote at the button end, it’s a bit trickey to get the slide switch put back correctly so try to open the remote gently so you can observe how it fits in.

When you say horn, you mean siren and not the car horn don’t you?

Dec

 

[Watchcame430]

I changed the batteries in the key but no luck. That was a year ago when I got the car.I need a new key I think.


It is the actual horn ... I have no siren of any type that I am aware of.


Very confused ... It's irritating because I want to see if I fixed the other issue but can't.


Next step is I am putting a brand new battery on the car to see if that helps by some miracle.


Not sure what else to do but getting tired of the issues now. It's pointless having it if I can't drive it.

 

[Dec]

Try a new remote fob battery and clean the remote fob battery contacts, the have no history of failure that I am aware off.
It’s very unusual to use the car horn on a Scorpion alarm, perhaps the siren is hidden somewhere.

Fill us in as to what the other issue is?

Dec

 

[mannikon]

With the Scorpion on my old W124 I had to reconnect battery with key at ignition 1. Might be worth a try?

 

[Watchcame430]

Try a new remote fob battery and clean the remote fob battery contacts, the have no history of failure that I am aware off.
It’s very unusual to use the car horn on a Scorpion alarm, perhaps the siren is hidden somewhere.

Fill us in as to what the other issue is?

Dec

I am not sure there is an alarm in my version of the fob. Just remote locking ... I think the horn might go off if door opened though.


The issue I have is rough running when warm. I didn't understand the diagnostics and bought an EZL in error.


Now realised it might be the purge valve which I cleaned and now can't test due to the horn issue developing.


I had cleaned the contacts and replaced the batteries in the key. Also bought a new key housing as it was falling apart.


On a positive I changed the indicators back to original today from the later clears.

 

[Watchcame430]

With the Scorpion on my old W124 I had to reconnect battery with key at ignition 1. Might be worth a try?

Thanks ... Worth a try but hadn't needed to up until now which is confusing..

 

[hotrodder]

According to the fitting instructions for the Scorpian 918 fitted to my w124 the siren was optional, i'm guessing with a V8 there isn't a lot of room left in the engine bay to bolt a siren so the horn was hooked up instead of activating the hazards with a siren?

 

[Watchcame430]

Could be ... Guessing as not certain it has an alarm but it kept going even when I removed the horn fuse.

Hoping the new fully charged battery makes a difference... Nothing else I can do that I have found so far..

 

[Dec]

I am not sure there is an alarm in my version of the fob. Just remote locking ... I think the horn might go off if door opened though.


The issue I have is rough running when warm. I didn't understand the diagnostics and bought an EZL in error.


Now realised it might be the purge valve which I cleaned and now can't test due to the horn issue developing.


I had cleaned the contacts and replaced the batteries in the key. Also bought a new key housing as it was falling apart.


On a positive I changed the indicators back to original today from the later clears.

Your remote, if it’s the same as the one in my picture is for an alarm, for example the slide switch controls the alarm as it can turn on or off the internal motion sensors and is wired into the vacuum pump so will operate the central locking.

Are you saying the remote fob now works? if not there is a way to switch the alarm OFF.
To switch off the alarm you would normally turn a round key in a Security Key Switch located in either the glove box or above drivers knees but usually located in easy reach of the driver and easy to find.

Now, you have no round key but you could by-pass the switch, to do that you would need to remove the switch from its mountings and by-pass the wires that go into the back of it, there might be either 4 wires or 2 wires on the switch.
The switch looks something like below.
Megatronix - RKL - Round Ace Key And Lock On/Off Two Circuit Switch: CAR ALARM DEPOT - FOR ALL YOUR SECURITY NEEDS

Image… 3A Key Lock Security Switch with 2 Round Keys - Safety Switches - Amazon.com

Dec

 

[Watchcame430]

Because the housing was damaged in the key I replaced it when I bought the car. The remote inside never worked so I am not certain.It looked like the picture you showed so assume it has an alarm. My memory could be wrong on the design of the original key.


What I do know for fact is the horn fuse was removed but the horn is going off when the battery is attached. Therefore some kind of alarm?


I believe once I opened the door in the past and the horn sounded so again assuming it has an alarm.


But no key/lock like you picture above and no alarm fuse in the fuse box.

 

[Watchcame430]

Just to add ... Mine uses button cells not the cylinder in the pic ..

 

[Dec]

There would probably be no alarm fuse in the fuse box as the alarms were usually after market and not factory fitted.

If your remote fob had button batteries then it’s not the same as my remote fob in picture.

Obviously you have an alarm alright, just no means to easley disarm it (remote fob) or switch it OFF, those old alarms usually did have some means to turn them OFF in the event of a malfunction, usually a key switch as described above. Have a look in engine bay in case there is a key switch in there somewhere, probably near the fuse box and may be concealed by a black dust cap.

The alternate solution is to find the control box for the alarm and unplug it. It could be located under the foot rest or behind the panel above drivers knees.

Dec

 

[BTB 500]

There would probably be no alarm fuse in the fuse box as the alarms were usually after market and not factory fitted.

Yup - there wasn't a factory fit alarm for the R129 AFAIK. My '97 has the official 'MBSS' (M-B Security System) but this was fitted after arriving in the UK, quite possibly by Scorpion.