Car alarm going off on start-up

[Mjolner]

Went on hols for 2 weeks, came back, battery dead. Started using jump leads, drove for an hour or so to recharge. Now the car hesitates a little before starting (as if there is only just enough battery power to turn over starter), then starts, at which point the car alarm goes off. Immobiliser unaffected, as the car will happily run with the alarm blaring. Not a good look, driving around in a GT3 with the alarm going off, not to mention loud - this must the loudest, most ear pearcing siren ever. Also the trip meter resets to zero. Naturally this only happens when I go for a late night or very early morning drive, much to the annoyance of the neighbours. Having tried it during normal waking hours, the car off course worked fine....

Before I hand the car and big wad of cash over to OPC to fix, is this likely to merely be a case of knackered battery? If so, can I just replace it, or is there some revenue generator Porsche has built in requiring electrics/alarm reset etc.

Sorry for the numpty question.

[DSM2]

Sounds like battery not fully charged.Go out at night with lights on, voltage falls, alarm senses that and goes off.

[Silver993tt]

you need to take the battery out and fully charge it. This will probably be an overnight job. Tha alternator in the car won't charge a battery fully if it's been run completely flat and jump started.

[giw12]

I had the same problem about a dozen times. Got bored waiting for the RAC and bought myself a CTEK charger conditioner thing. No problems since. Never had to replace the battery though but I'm sure an OPC would recommend you do.........

[Henry-F]

As has already been said charge the battery properly overnight with a mains charger and see how you go. You may need to replace the battery but have a go charging it first. If it`s a genuine Porsche battery there should be a date stamp on top of one of the terminals (year/week), if it`s older than say 3 years then you may end up changing it but charge properly first.

Henry

[Nurburgsingh]

stop trying to nick your neighbours car!!!

[Mjolner]

Thanks for your assitance. More numpty questions:

Is the alarm only powered by the main battery or does it have a backup somewhere? I know this is not rocket science, but suspect I will be slapped with an ASBO if I attempt this feat when I return home this evening and the alarm goes off again when attempting to disconnect the main battery. Can I not leave everything connected and slap the mains charger on it, or will that blow all the electrics?

Thank you,

Your local car mechanic.

[giw12]

I can only speak for the charger I've got (a CTEK) but there's no need to remove the battery. Can't imagine any of them needing you to do that.

Buy one, read the instructions, switch it on and wait for 12-18 hours.

[richardb.jones]

Mjolner said:

Thanks for your assitance. More numpty questions:

Is the alarm only powered by the main battery or does it have a backup somewhere? I know this is not rocket science, but suspect I will be slapped with an ASBO if I attempt this feat when I return home this evening and the alarm goes off again when attempting to disconnect the main battery. Can I not leave everything connected and slap the mains charger on it, or will that blow all the electrics?

Thank you,

Your local car mechanic.

No need to remove the battery - but if you do (no power for charger etc) then put the ignition in position 1 before you remove the terminals - then the alarm will not go off ..