Alarm

[honoria1]

After I topped up the washer fluid and checked the levels and shut the bonnet , I set the alarm on my S-Type two days ago. Within 5 minutes the alarm went off for no apparent reason. I turned it off with my key and reset it . 5 minutes later it went off again. The display was running through a number of faults and the engine fault light was on. As it was 9 pm I decided to leave the car unlocked over night. The next morning I started it up- no faults displayed and no engine light. I reset the alarm and have had no repeat of the alarm going off. Could I have disturbed some thing when I had the bonnet up? Would appreciate any ideas. Mike (honoria1)

[J44EAG]

Hello Mike.

These cars do get gremlins occasionally. Some reset themselves quite easily with little owner input needed.

As to what can cause these issues, there are several that can affect locking and security systems..

Firstly check to see that all windows and the sunroof are fully closed. Run windows and roof open and closed a few times.

Secondly, door locks. Open and close a few times and double lock on each occasion. Having done all that, the system should settle down again.

Thirdly, check that the boot is shut and locks well. Whilst in the area, check terminal voltage at the battery. You should see around 12.8 volts. If not, you could have a low voltage which might point at an aged battery. The car is heavily dependent on voltage to drive its complex systems and low voltage often causes issues with ABS faulting, cycling door locks, flashing headlights and indicators and dropping door glasses and the horn sounding off.

Double door locking puts the car in its lowest current draw situation and allows the car systems to fully close down after about twenty minutes. Similarly, the systems boot up and run through diagnostic program quickest on start up if you have double locked the car when last used.

I suspect that an everyday diagnostic may not have successfully completed when you encountered your incident. The fact that you are now all ok suggests that you encountered a minor blip which has self healed and have not been left with any dash message which suggests a trip to a diagnostic garage for interrogation will not be needed.

These things do happen from time to time as occurred to me recently when my car threw a wobbly and the central locking went bonkers. That madness self healed and I`ve had no further issues since. Hopefully that will be the same for you.

Mike K.

[honoria1]

Thanks Mike
The alarm went off again this afternoon. Engine malfunction light on again. I thought I'd check the battery age and ended up baling out a bucket of water fr om the boot. I suppose this won't help. Taking the car to my local independent in the morning. He says the alarm will have registered the fault. Will let you know how I get on. Thanks again for the reply. Mike

Hi Mike. Your advice took away the engine malfunction light. As I was taking the car in to my local independent anyway I asked them to do a fault test on the alarm. The test came up as 'no fault recognised' on the six occasions it had gone off. The mechanic surmised that the backup battery (battery back sounder)for the alarm has a terminal which can corrode on an older car ('52) plate so they normally disengage this battery because it isn't needed. Re- chargeable batteries the size of those in cell phones don't normally last 11 years anyway. A battery in such a state can cause the alarm to go off. The battery was disengaged and things have been fine since- touch wood! Regards Mike.