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355 alarm problem

R

runnyg

New member
For a couple of weeks the alarm on my 355 has not been making the usual bleeping noise when being locked/unlocked although the central locking is working fine. The car is garaged overnight and rarely left for long when not at home so I wasn't stressing too much about this and planned to have it rectified at the next service.

I've just noticed that the red dash light is remaining on constantly. Is this to warn of a system problem connected to the lack of alarm noise and will it cause any further problems if not addressed ? The car is on a trickle charger and has a new battery.

Cheers
Doug
 
Search for 355 alarm battery. Common fault. Mine has been like it for the last few years.



Don't worry about all the 348 results the search returns....it has the same problem.
 
You need a new alarm siren, the battery in your existing one is dead and has probably leaked over the circuit board meaning that replacing it will not be possible.

There are lots of threads showing you how to do a replacement but these all come with the caveat that your circuit board is OK. I spent quite some time buggering around cutting my alarm unit open on the 355 last year and doing the same with some old second hand ones I managed to find once I discovered my original unit was knackered. None of them were any good in the end so I had to just buy a new one - speak to Tim at Walkersport, he carries them in stock for a reasonable price.

Easy thing to change, take off the front NS road wheel, remove the under arch metal panel at the front of the car and hey presto the alarm siren is sat there waiting to be unplugged and replaced.
 
Alarm

I had the same problem with my alarm.Stripped it down,clean the circuit board with IPA,searched e bay for replacement battery.Found a battery ok but the 2 pin connector u/s so soldered the original plug on making sure of pos. and neg was checked as the colours were not the same.Re assembled alarm and fitted it loosely to check operation.It had to let the battery charge up awhile,but it worked fine after that and beeps a treat now.Only problem is the dash red led is on when driving.Hope this is of help Graham
 
Guys, thanks for all your advice.

I had seen some of the previous posts but not seen anything connecting the red dash light with the alarm siren.

Cheers
Doug
 
If your alarm just recently stopped working, you may have a good chance at saving it if you act soon. After a number of years the batteries won't hold a charge and, with some luck, that will happen to you before they spew their guts onto your circuit board. If the batteries are shot but have not yet started leaking, you are lucky. I say cut the thing open now and see if one of the several battery mod threads will allow you to fix it yourself. This isn't difficult if you have basic soldering skills and can tell plus from minus on a battery.

In my case, the previous owner ignored the problem and by the time I cut mine open, it was too late. Fortunately, the dealer mailed me a new alarm at no cost to me. By the way, I was disappointed that the red light on the dash remained on after the fix. But it turned out that the new component just needed a lot of charging. After after a few days, the light started working properly.
 
Mozella said:
If your alarm just recently stopped working, you may have a good chance at saving it if you act soon. After a number of years the batteries won't hold a charge and, with some luck, that will happen to you before they spew their guts onto your circuit board. If the batteries are shot but have not yet started leaking, you are lucky. I say cut the thing open now and see if one of the several battery mod threads will allow you to fix it yourself. This isn't difficult if you have basic soldering skills and can tell plus from minus on a battery.

In my case, the previous owner ignored the problem and by the time I cut mine open, it was too late. Fortunately, the dealer mailed me a new alarm at no cost to me. By the way, I was disappointed that the red light on the dash remained on after the fix. But it turned out that the new component just needed a lot of charging. After after a few days, the light started working properly.
Click to expand...

I cut my alarm unit open within days of it stopping working and the battery had still leaked :-(

But it is sage advice, you have nothing to lose, cut your existing alarm open using a sharp Stanley blade by running it around the seam continuously until it breaks open and see what you are dealing with
 
Hi
I had the same problem as you, having read previous posts I decided to "have a go". I took the siren out and cut it around the join then realised that there are four philips screws holding it together :mad: you will probably find there is silicone in the screw holes, it comes out quite easily with a small screw driver.
The battery was shot as you can see I ordered a replacement from RS (RS part No 325-2888), I removed one cell from the stack as the voltage is too high, use the minimum amount of heat when soldering the wires on.

355 alarm battery-2.jpg

I made up a new cable and fitted a new 2 pin molex header and socket as the old one had corroded.
Then reassembled with some silicone RTV around the join and bobs your uncle!

355 alarm battery-1.jpg

The new batteries are NiMH as you can't get NiCd anymore but that wont matter as they both have similar charging characteristics.
Hope this helps.

Regards
Rob
 
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