996 mech help please - Page 1 - 911/Carrera GT - PistonHeads UK

Hi, hoping you can help me, a friend and neighbour has a 996 convertible, C2 I think. He has sadly been diagnosed with early dementia so I said to him we must try and get his Porker out while he can, I've never seen it started in the 6 years we've been neighbours but he thinks he last drove it about 3 years ago. The problem as far as I can ascertain is that there is a red light that stays on on the dash and I think the battery discharges whilst driving, his wife tells me he took it to a Porsche specialist who said it needed a new binnacle, which he bought 2nd hand but has lost confidence in his abilities so the car has just stood. He bought a new battery about 6 months ago but thats still on his workbench, finally managed to have a brief look this afternoon and the front boot is open, so went to look at the old battery to make sure the new one is the right spec and the old battery is missing, presumably he took it out to check the size/output , no idea really. Spec of new battery is an 80ah, 780amps. I talked to a 996 owner at a car show who said the convertibles have a different battery to the hard tops, so is this the right battery ? To me a red light on the dash is unlikely to mean swapping the dash ! sounds like a charging issue but till the new battery is charged and in I won't know. So questions while this progresses..... Is the new battery the right spec ? Are there any known issues with the dash lights, probably a red light? Leaving the car without a battery for several months, is this going to be an issue ?If so can it be resolved ? I understand from the owner I spoke to that if a battery cell drops down the charging light can stay on as the right voltage is never obtained , is this correct? Really appreciate any help with replies/pointers and I'll update when I get any further

If the battery physically fits in the space then it will be fine. Should be no problem leaving the car for a while without a battery, might need to reset window stops etc but all minor stuff. No idea about the red light, I would get the battery connected and see if it runs. Just remember to disconnect the battery when you have finished (and leave the bonnet open).

MartinB7 said: Hi, hoping you can help me, a friend and neighbour has a 996 convertible, C2 I think. He has sadly been diagnosed with early dementia so I said to him we must try and get his Porker out while he can, I've never seen it started in the 6 years we've been neighbours but he thinks he last drove it about 3 years ago. The problem as far as I can ascertain is that there is a red light that stays on on the dash and I think the battery discharges whilst driving, his wife tells me he took it to a Porsche specialist who said it needed a new binnacle, which he bought 2nd hand but has lost confidence in his abilities so the car has just stood. He bought a new battery about 6 months ago but thats still on his workbench, finally managed to have a brief look this afternoon and the front boot is open, so went to look at the old battery to make sure the new one is the right spec and the old battery is missing, presumably he took it out to check the size/output , no idea really. Spec of new battery is an 80ah, 780amps. I talked to a 996 owner at a car show who said the convertibles have a different battery to the hard tops, so is this the right battery ? To me a red light on the dash is unlikely to mean swapping the dash ! sounds like a charging issue but till the new battery is charged and in I won't know. So questions while this progresses..... Is the new battery the right spec ? Are there any known issues with the dash lights, probably a red light? Leaving the car without a battery for several months, is this going to be an issue ?If so can it be resolved ? I understand from the owner I spoke to that if a battery cell drops down the charging light can stay on as the right voltage is never obtained , is this correct? Really appreciate any help with replies/pointers and I'll update when I get any further Hi, the battery tray in a 996 has 2 bolt holes to accommodate the fixing clamp for 2 different sized batteries. If you enter the car’s registration number into a battery or car parts supplier, it’ll confirm the correct battery type for your car. Regarding the red warning light, without seeing it I can’t be sure, but a charging light would be consistent with the fault you describe. The alternator (or most likely the voltage regulator on the alternator) may have failed causing the battery to drain as it isn’t being charged. Replacing the alternator isn’t a major job with the right tools. Airbox off, and remove the drive belt and you’re almost there. Plenty of online videos if you fancy attacking the job yourself. A quick way to diagnose the alternator is to check the volt meter on the dash binnacle. Should read around 12v with ignition on (and engine not running), and then around 13.5 to 14v with the engine running (this depends on the load on the electrical circuit) Hope this helps

IREvans said: MartinB7 said: Hi, hoping you can help me, a friend and neighbour has a 996 convertible, C2 I think. He has sadly been diagnosed with early dementia so I said to him we must try and get his Porker out while he can, I've never seen it started in the 6 years we've been neighbours but he thinks he last drove it about 3 years ago. The problem as far as I can ascertain is that there is a red light that stays on on the dash and I think the battery discharges whilst driving, his wife tells me he took it to a Porsche specialist who said it needed a new binnacle, which he bought 2nd hand but has lost confidence in his abilities so the car has just stood. He bought a new battery about 6 months ago but thats still on his workbench, finally managed to have a brief look this afternoon and the front boot is open, so went to look at the old battery to make sure the new one is the right spec and the old battery is missing, presumably he took it out to check the size/output , no idea really. Spec of new battery is an 80ah, 780amps. I talked to a 996 owner at a car show who said the convertibles have a different battery to the hard tops, so is this the right battery ? To me a red light on the dash is unlikely to mean swapping the dash ! sounds like a charging issue but till the new battery is charged and in I won't know. So questions while this progresses..... Is the new battery the right spec ? Are there any known issues with the dash lights, probably a red light? Leaving the car without a battery for several months, is this going to be an issue ?If so can it be resolved ? I understand from the owner I spoke to that if a battery cell drops down the charging light can stay on as the right voltage is never obtained , is this correct? Really appreciate any help with replies/pointers and I'll update when I get any further Hi, the battery tray in a 996 has 2 bolt holes to accommodate the fixing clamp for 2 different sized batteries. If you enter the car’s registration number into a battery or car parts supplier, it’ll confirm the correct battery type for your car. Regarding the red warning light, without seeing it I can’t be sure, but a charging light would be consistent with the fault you describe. The alternator (or most likely the voltage regulator on the alternator) may have failed causing the battery to drain as it isn’t being charged. Replacing the alternator isn’t a major job with the right tools. Airbox off, and remove the drive belt and you’re almost there. Plenty of online videos if you fancy attacking the job yourself. A quick way to diagnose the alternator is to check the volt meter on the dash binnacle. Should read around 12v with ignition on (and engine not running), and then around 13.5 to 14v with the engine running (this depends on the load on the electrical circuit) Hope this helps 13.5v-14v might be a bit optimistic, 996s have an issue with the alternator wiring/connectors degrading that means the alternator can't push out the full voltage it's generating, as long as it goes up on the dash when it's running you should be ok to drive it - mine ran at 12.5v for a couple of years with no issues until I replaced the cable as part of other work and it now shows 14v. This might also show itself as a lazy starter when hot. Pic of the offending warning light would help enormously if you can get the battery charged and it started.

toastyhamster said: 13.5v-14v might be a bit optimistic, 996s have an issue with the alternator wiring/connectors degrading that means the alternator can't push out the full voltage it's generating, as long as it goes up on the dash when it's running you should be ok to drive it - mine ran at 12.5v for a couple of years with no issues until I replaced the cable as part of other work and it now shows 14v. This might also show itself as a lazy starter when hot. Pic of the offending warning light would help enormously if you can get the battery charged and it started. Indeed. And as you’ve noted, you’re looking for a voltage increase on the voltmeter once the engine is running. 13.5 to 14v on the display is normal at idle. Another potential fault the voltmeter will highlight is a failed voltage regulator on the alternator, here you’ll either see a fluctuating voltmeter needle, or a reading exceeding 15v

Where is the SE are you as I am in Kent and a bit of a tinkerer. I have changed the volteage regulator on mine a few years ago and may be able to assist depending on where you are. As others have said a picture of the light may help. Pip

Small note if you're messing with batteries - there is a backup for the alarm siren that will start charging up once you connect a new one. If you're going to disconnect the battery again, make sure the ignition is on when you do, this will stop the alarm sounding.

Also, you may get abs and stability errors come up at first when the new battery goes on but a few mins of driving resets it.

Update….it works ! I charged the battery, popped it in and first turn of the key she fired up. I’ve checked alternator output and it’s sitting at a constant 13.93-13.95v I’ve found out a little more of the history, apparently the car always starts ok but when out for a drive a red light, presumably the charging light, comes on and the battery drains. I think it would probably be wise to swap the alternator for peace of mind as intermittent faults can be a pain and this would give him confidence to go out. We’ll put my Elise in his garage and bring the 996 down to mine where there’s more room. Be interesting to see the relative difference in size. Where’s the best place to pick up an alternator, presuming they’re readily available. Really appreciate the help, thanks

MartinB7 said: I’ve checked alternator output and it’s sitting at a constant 13.93-13.95v I’ve found out a little more of the history, apparently the car always starts ok but when out for a drive a red light, presumably the charging light, comes on and the battery drains. If it's producing the correct output then the alternator is unlikely to be at fault (unless it's overheating). I'd check that the y-cable is not degraded. It usually manifests itself as being sluggish or not starting when the engine is hot. I'd also check if the auxiliary belt is tight and isn't stretching when it's hot. Easy (and cheap) to replace with the airbox out. Whilst there have a look at the pulleys and tensioner, not too expensive in parts but they can fail (I know from experience) so worth looking at changing those with the belt if they don't move freely/have play in them. Edit: this is presuming you've changed the battery for a new one. Edited by Sublime on Monday 22 August 14:16

Apologies to anyone I haven’t replied to directly, we’re near Westerham. Thanks for the tips all, yes the battery is new and charged, the car came out the garage and received a good wash, it’s now back in his garage and next step is a new MOT probably later in the week, giving it a little run out will hopefully highlight any underlying issues. The car desperately needs using, I checked the mot history and it’s covered 1600 miles in the last 10 years !

MartinB7 said: Apologies to anyone I haven’t replied to directly, we’re near Westerham. Thanks for the tips all, yes the battery is new and charged, the car came out the garage and received a good wash, it’s now back in his garage and next step is a new MOT probably later in the week, giving it a little run out will hopefully highlight any underlying issues. The car desperately needs using, I checked the mot history and it’s covered 1600 miles in the last 10 years ! It will likely need new brake fluid and some new oil if not been done.