997.2 C2 electrics failure

[Will.birkinshaw]

I have just tried to start the engine of my 2009 997.2 C2 after a layup of about 4 weeks in a garage on the ground floor of my house. The garage is not damp.Neither the temperature nor the humidity in the garage should have been abnormal. Other than this, the car has behaved itself perfectly up to this point.
The battery has been on charge during this period with a CTEK MSX 5.0 charger so, for the moment I am assuming that the battery is OK.
When I turn the ignition key beyond the ignition ON position (to start the engine) there is the sound of a relay clicking about 2 times per sec, the whole dash display flashes on and off and the engine does not turn. On returning the key to the ignition ON position, the yellow engine warning light is ON, together with several other warning lights and the ABS failure and PSM failure warning lights appear one after the other. Also the electric windows do not operate when opening and closing the doors.
Any suggestions of things I could try before resorting to getting it towed away!!

Thanks
Will

 

[irb26]

Your battery sounds flat or there is a poor connection from one of the main leads.
Stick a voltmeter on it (battery) and see what the voltage is with the CTEK disconnected if its lower than about 11V then i the battery is probably discharged or incapable of holding a charge.

 

[Blade_uk]

When my 997tt battery gets low it starts flashing random dash light & windows start moving, does get a little crazy, good battery charge overnight and its all good again for a few months

 

[JCX]

Check your fluid levels in the battery... people criticise the Moll batteries but if the fluids are maintained then it's a champ. If not, it's a chump.

 

[RCS]

I suspect duff battery.

Whats age of battery? I suspect that CTEK's and the like if used regularly can hide a failing battery. We had a Boxster on a CTEK, all seemed fine, absolutely nothing on trying to start, battery had failed. New battery from ECP and job was a good 'un. I now periodically leave the CTEK off and see how it sounds on starting a week later. Hope thats all it is!!

 

[andyc11]

As above, my 997 GTS had exactly the same symptoms with a flat battery. If you have Porsche assist, they’ll send the AA to confirm and recover to OPC (or get it going to get you there if you’re able to do that).

 

[STiG911]

Yep, your battery is shot. Even though it shows as fine on the charger as having a good voltage, it actually has no amps anymore which is why your cars dead - the exact same happened to me last year. Time for a new battery.
(If you're not under warranty I really do recommend Tayna Batteries at https://www.tayna.co.uk/ - delivery in 1 - 2 days and pricing to good to pass up)

 

[ralphmusic]

Not to rain on a parade, but Tanya recommend a wet battery for my 981CS (I know it is not a 997.2) which actually needs an AGM battery because it has Stop/Start 'feature'

Design911 have batteries listed as Porsche OEM but they lack Porsche marking so are equivalents, not OEM..

... so as always best to double check specifications.

 

[Will.birkinshaw]

Thanks for all the suggestions. Does look as though I was being fooled by the CTEK charger. There is plenty of liquid in the battery and it does take 5amps from the charger (for the relatively short period during which it appears to be charging) but the voltage falls rapidly as soon as any significant current drawn. The battery is 7yrs old so perhaps I should be thankful it has lasted this long!