355 alarm siren repair

My dash LED was staying on indicating a problem with the alarm system. After checking all the posts on this subject, I decided to remove the alarm siren and check the internals. Mine is a 97 spider, and the siren was the older part number (one with the pigtail connector). I was surprised how easy it was to open the case and remove the battery. Unscrewed two screws under the silicone plugs and the case just fell apart. Inside is 7.2v NiCad battery. I tested the voltage and it was 8.4 volts. No sign of acid leaking until I removed the plastic coating. Search the internet long and hard and found one place in the UK which could supply the NiCad battery in the same voltage but slightly higher mAh rating. I placed an order for the battery and waiting for the part to arrive.
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I ordered the battery from ESP special batteries In the U.K.


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The siren was located next to the windscreen washer bottle in the LHS bottom bumper. You need to remove the wheel, the under guard fibre glass panel and then the flat vertical panel in the wheel well. After reading all the posts on this siren, it seems some cars were fitted with the later (new) version siren which was fitted to the 360 and some of the other V12 models around the late 90s and early 2000s. This version requires a second cable to plug into the siren and then into the car harness. My advice is don't just buy the new part without checking the old one first (if you have the older style like mine). I understand the new one has a NiMh battery which also leaks and destroys the internals. The new one is also very difficult to open. My siren was very easy to open, no cutting involved. It looks like it was made to be serviceable, unlike the new one. I thought about buying the GM siren too, but there were conflicting posts about whether this unit works properly, even though is looks identical to the Ferrari part. You also need the adapter cable too, which is not cheap. Plus, those that fitted the GM siren say it sounded different to the ferrari unit. That would slightly annoy me, particularly after listening to mine for 10 ten years.

 

I did find a NiMh replacement, but i wanted to stay with the NiCad because i wasn't sure whether there would be issues with swapping over to NiMh. Plus, i had got over 20 years life with the NiCad battery.

 

how long was the LED staying on before you got to the battery? I got onto mine only a few weeks after i noticed the LED staying on, hence the acid was relatively contained.

 

Did battery world supply a bosch GM part?

 

oh ok, now I understand, you paid $80 for a replacement battery in NiMH. I ended up paying around $30 AUD to get the right battery from the UK (still waiting for it to arrive). I have to solder the tiny pug on to the battery when it arrives, before putting it back into the siren. I think we're lucky to the siren with this battery, at least its a straight forward job. The later version Ferrari sirens fitted to the 360 and some late 355s (I understand) have the battery solder on and is not really serviceable like our one.

 

New replacement battery arrived and all back together. I had to solder the old connector on to the new battery. The negative wire was quite corroded but I had to use it because I had trouble getting a replacement mini connector. Next I will be putting back in the car to see if the LED has gone out.
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Yes, replaced the alarm siren and took the car for a drive this weekend, happy to report all good and the LED light does not stay on while driving.

Just to note, when i disconnected the siren the first time, it did not go off (no sound). With the new battery, doing the same thing made the siren scream, so i had to reconnect and disarm using the remote. Also, during the repair, i did not disconnect the main battery.

 

yes good idea, if yours has lasted all this time, i would change it. Its likely to have corrosion on it now, but still working. Mine was original and the battery lasted 20 years. I would go for the NiCad battery, they are really hard to get but at least they will last another 20 years. The place i got it from were great, they sent it straight away but it still took over a week to arrive.

 

when i disconnected the siren for repair, it did not make any sound. Presumably this was because the backup battery had failed (although it did have a voltage of 8.4V when i tested it later). When i put the siren back in the car after repair, i connected it to the wire harness on the car. All good at this stage, no alarm going off. I then disconnected the siren cause the wire was tangled, and then it went off (alarm sounding). So i then connected it back and hit the button in the fob to stop the noise.