MBSS woes

[Doodle]

This nearly resulted in a Basil Fawlty style car-thrashing in the middle of the company car park this morning.

Coming back to the car at the petrol station just around the corner from work this morning, unlock the car with the remote and open the door, at which point the alarm goes off. Brain not in gear, I stuff the key in the ignition and turn to make it shut up (the fastest method for my old car), and to my surprise the car starts.
The alarm is still wailing away, so I finally managed to silence it using the alarm key in the humourously position slot in the glovebox.

Get in the car, start up and drive off. As I'm pulling back onto the road from the forecourt, the alarm goes off again, so I continue the 300 yards to work, park up and stop, and disarm it again. It goes off again as I start taking stuff for work out of the car, and finally only shuts up for good when I close everything and walk away swearing!

I'm not sure if I'm doing anything wrong (the instruction manual is woefully vague), and it doesn't happen that often (the 2nd time in 9 months). The ability to start the car while the alarm is going off worries me, as does the fact that it goes off while driving (although the car kept going, I have had an alarm shut everything down in the outside lane of a de-restricted autobahn, which was )

Any ideas? Is it me being a clot, or is just (as I suspect) the alarm being crap?

 

[Shude]

The instruction manual is vague because there was no integrated alarm on the R129 in 1995, what you have is a factory/stealership installed oem-style alarm which as any W124 owner (same boat) will tell you is pretty poor.

I believe the usual method of fixing this is to take it to a recommended car-electrician and have the old one removed and a branded or recommended kit installed...

 

[tim.100]

Is this your 202? I had numerous problems with mine, resolved by short-circuiting the bonnet switch. (For the record, this is now fixed properly!) My other car also had issues, and here is my generic list of problems and fixes:

1. Bonnet release switch
2. Dead sensor
3. Moth in car
4. Seat belts not retracted
5. Close air vents when not in car
7. Put Blue-tack on the ultrasonic sensors
8. Voltage drop – change battery

At this time of year, no. 8 is a good candidate.

Another specific fix for the W202 is issued by MB as a Technical Service Bulletin. It involves fitting small cast iron chokes around the sensor wires in the car. This reduces spurious alarms caused by radio interference. I bought the chokes from Mapin, although MB do a kit.

Regards,

Tim

 

[Doodle]

Yes, this is the 202, I should have made that clear. Ironically, the 129's alarm has issues of a different kind (new key will not program), but at least publically it behaves itself, and only causes the dealer hassle. I am tempted by Shude's solution of a different alarm system, from a proper alarm manufacturer.

Given that it's only twice in 9 months, I'm wondering whether it's just me being a clot on an early morning. The battery I know is good, so that should be ok. Unfortunately unlike my previous Honda, there does not seem to be a diagnostic LED to allow me to check which circuit is triggering it.

I guess the proof of the pudding will be in about 4 hours when I leave work!

EDIT: Looks like the alarm is ronnied. Just went out to get the manual, the alarm was fine with opening and closing the door, but as I opened the boot, off she goes. Reading the manual, it should have shut off when the ignition was turned.

 

[Shude]

Looks like the alarm is ronnied. Just went out to get the manual, the alarm was fine with opening and closing the door, but as I opened the boot, off she goes. Reading the manual, it should have shut off when the ignition was turned.

Is your W202 pre-facelift or facelift? If it has a flip-type key then it's pre-facelift and my previous comments about the alarm system are still valid, the pre-facelift alarms aren't bad but can be a little delicate.

 

[Doodle]

Yup...pre-facelift, but only just.

Judging from the varying delay between what should be an alarm triggering, and it actually going off, the fact that it really shows no interest in disarming when it's supposed to, and that it's previous owner (my grandmother) had been having similar problems with it for some time, I'm guessing it's dead.

It's probably going to cost nearly as much to look into and sort out as it is to de-install and refit a proper unit in it's place. Current fave is a G5 Clifford with Intellistart.

 

[Shude]

Yup...pre-facelift, but only just.

Judging from the varying delay between what should be an alarm triggering, and it actually going off, the fact that it really shows no interest in disarming when it's supposed to, and that it's previous owner (my grandmother) had been having similar problems with it for some time, I'm guessing it's dead.

It's probably going to cost nearly as much to look into and sort out as it is to de-install and refit a proper unit in it's place. Current fave is a G5 Clifford with Intellistart.

One of the most common reasons the alarms fail is that they rely on the flashing LEDs in the handles/mirrors to know when the car has been locked/unlocked - this isn't a joke. If an LED fails then the alarm won't work properly.

IIRC there is a pretty good thread on this forum about making repairs to the pre-facelift alarm system, Koolvin had problems and had to do some soldering or other hardcore mod to get the alarm to work again - the stealership parts guys said they had to get an electrician in to remove/replace an LED rather than replace the whole unit because availabilty is low and expense is high for those items.

Simple answer is to have the thing disabled/removed and get something decent installed, that's what I'd do anyway!

 

[Doodle]

Lol...that may have something to do with then...the red LED in my mirror is dead. Perfect excuse for a auto-dimming RVM in my mind, although I'm still giving a new alarm serious consideration.

 

[Dieselman]

IIRC the mirror and door handle lights are bulbs, not LED and as such need to show continuity to the alarm for proper operation.
Your problem may be either the mirror bulb or water in the alarm module, which is in the floor of the foot well IIRC.

 

[r129 300sl]

Early R129 SLs did have Factory fit alarms that activate with the IR key. However these have not got immobilisers. They are merely voltage drop activated and will you can start car with alarm sounding and indicators flashing.

For insurance purposes you will need immobiliser.

 

[Doodle]

Thanks guys, but as above, the 129's alarm is behaving itself (apart from issues with programming the new key, but the dealer is sorting that one, hopefully)...the problem is with the 202. I think Shude may have hit the nail on the head here, so I'm going to try a new RVM first.

Still useful information though, and has been noted for future reference :bannana:

The SL is a 95, so does have an immobiliser (and I've tested that it works). Our insurers have never requested that an immobiliser must be fitted though, so that statement isn't strictly true. However I would never own a car without one.

 

[BTB 500]

For insurance purposes you will need immobiliser.

FWIW I told my insurance company my R129 had MBSS fitted, and they weren't even remotely interested

 

[MickeyM]

IIRC the mirror and door handle lights are bulbs, not LED and as such need to show continuity to the alarm for proper operation.
Your problem may be either the mirror bulb or water in the alarm module, which is in the floor of the foot well IIRC.

Had same problem and managed to change the bulb in rear view mirror. This is tiny and is surface mounted to pcb in a small white resin clip. Tease this off with a knife, the soldered joint gives up after a few wiggles. The bulb is identical to ones used in some old video players, a 12v 3mm sub miniature, easy to find on eBay. Thread the leads through the clip and re-solder to board, making sure leads are caught on the solder pad. There are already posts around describing mirror removal and opening. Much cheaper than a new mirror! Good luck.

 

[markmifsud]

Had same problem and managed to change the bulb in rear view mirror. This is tiny and is surface mounted to pcb in a small white resin clip. Tease this off with a knife, the soldered joint gives up after a few wiggles. The bulb is identical to ones used in some old video players, a 12v 3mm sub miniature, easy to find on eBay. Thread the leads through the clip and re-solder to board, making sure leads are caught on the solder pad. There are already posts around describing mirror removal and opening. Much cheaper than a new mirror! Good luck.

Hi MickeyM, I hope he did get it fixed as it was some 14 years ago

 

[MickeyM]

Yep, I did notice! Just for the benefit of any other classic geeks like me with the same problem now.

 

[Doodle]

To be honest, I can't remember. I assume I must have fixed it as I had the car for another couple of years, before it was p/x'd and ended up exported somewhere.