Voltage/amps gauge query/help

Hi all Wondered if I could ask for your expert advice ?! On a road trip to Wales currently in the 996 (I'll post more on that in separate thread when back later :grin: ) and have noticed that after a sustained period of driving (circa over 2hrs) my voltage gauge seems to drop really low. This has happened for the last 3 days in a row and sometimes it drops down then seems to return to normal levels (just under 14) under its own accord. Sometimes it'll drop, then go back up a little then drop again and stay low. When the car is left overnight and started again, it seems to read normal again for a while then do the same again. Touch wood it's starting ok at the moment. Anyone had anything similar or have any ideas? I'll book in to garage when back but thought I'd ask here 1st :thumb:

I'd guess at the infamous 'Y" cable (engine bay 12v supply) breaking down with heat and corrosion and dropping more voltage as it heats up with the engine. It could also be the voltage regulator which get a bit sketchy with heat and age. Both are DIY but a bit awkward. If it starts and runs ok you'll probably be alright until you get back.

Mine was very similar and it was the bosch regulator, I changed it for an aftermarket reg and have had 13.5 - 14v ever since, and much better starting. With the old reg I had about 13.5 when first started and it took about a half hour to drop to about 12.5 at which point it was no longer charging. At first I though I wasn't doing long enough journeys but eventually realised the longer I drove the weaker it was on the next start, that's if it did start at all, and if I left it on the ctek it started much better. It just seems to be a characteristic of the Bosch reg, some people have bought a new bosch alternator for over a grand and had the low voltage problem within 6 months. Saying all that I know the na 996 does have the common y cable fault too. It would be nice to measure the voltage on the rear of the alternator, if is higher than the dash gauge then that points to the cables, if the same then the alternator reg is more likely. Mac

Never been sure what the point of that gauge is to be honest. Had two batteries fail over the years in 4Ss, never had any indication from the gauge. What is the gauge actually measuring?

I always thought it was charge voltage of the alternator.

Thanks so much for all you're responses. Very useful! Just home (West Sussex) after 7hr drive back from Snowdon and the gauge behaved today but will see what garage says and will certainly mention 'Y cable" or the voltage regulator :thumb:

Visited Precision to get alternator voltage and battery checked today and great service as normal. 911uk's very own Iain (deMort) checked both battery and alternator and got get expected readings on both and said wouldn't necessarily go down the new battery / alternator route just yet, unless I start experiencing notable problems. He thought it might likely be a faulty gauge and also said to take these gauge readings as a rough guide only as they're not always an accurate reading. I enquired about replacement gauge and he said it'd be down as a replacement cluster so won't do that just yet (£££) Mentioned 'Y cable' but thoughts were this was more common on 997 and not usually a 996 issue with this. Advice was to monitor and do nothing for now unless I start seeing battery / power / starting issues. Great service from Precision and good to finally meet you in person Iain - thanks very much for looking at my car :thumbs:

Yep! I was about to head off to Italy in my GT3 the other year. Gauges all fine but my Indy checked the charging as a precaution (having had another customers alternator fail, out in Europe) and my alternator was kaput. No indication from gauge and no battery light on dash. Pretty pointless really. Even my Vauxhall Nova first car, 25 years ago threw a dash light when it wasn't charging. :grin: PM'd you back, Adam. :thumb: