centexsi

I had a similar problem awhile back - voltmeter would read mid-12's sometimes, which I thought was too low with car on. I installed a new alternator (was original, 64k miles) and it didn't make a bit of difference in my case. My gauge fluctuates between 12.5 and 13v and has never had any warning lights on so I'm going with "all is well".

dprantl

If my car did this with a brand new alternator, I would be testing all the ground wires.

Dan

centexsi

I did do that when I pulled the engine for coolant pinning. Took off every single ground wire, cleaned and lightly roughed up with steel wool, cleaned again and hooked everything back up. Didn't make a difference when I got the car back together.

Macster

Based on my experience I'd say all is well, too.

Reviewed hundreds of logged trips from my 2003 Turbo from way back in Jan 2015 to present. Battery voltage was logged every 5 seconds and the volage level ranges from just under 14V to just above 13V with the range mostly confined to betwen 13.8V and 13.3V.

The higher voltage level is after cold start and is with no additional electric loads. The voltage drops after some minutes of driving as the battery gets topped up.

The lower voltage level is with an additional electric load, or loads. The "worst" case is with the A/C on along with the head lights.

What I have found is the car needs about 3 usages a week in cold weather and 2 a week in mild to hot weather. For me it just so happens that my 30 mile work commute appears to be "perfect". 30 miles of driving mostly on the freeway though unfortunately not always at freeway speeds due to traffic. But the backup is generally limited to a couple of miles. The plus to this is the commute takes longer than 30 minutes.

Generally I try to take the car when I know I won't have to go out for lunch so the car doesn't get subjected to a lunch run with an engine start, followed by 2 miles or so of driving then a short while later another engine start followed by the 2 miles back to the office. But even if I do end up making a lunch run this doesn't seem to have any real impact as the drive home is long enough to top up the battery.

This 3 or 2 usages a week keeps the battery topped up. I haven't the option of using a battery maintainer so I have to keep the battery topped up with regular usage.

manimal

That's good to hear. I see similar behavior, as well. After a cold startup, the gauge will read close to 14v, but after driving for a while, it will dip down to just above 13v.

Guess I'll leave well enough alone, for now. Thanks for everyone's info.

dprantl

Just above 13v is fine. It's when it goes below ~12.7v that the charging system is unable to keep up with the car's electrical load and the battery begins to be discharged instead of charged.

Dan

Kevinmacd

I just replaced my voltage regulator today, since when the AC was on the voltage would drop to 12.58 volts. The new regulator now with the AC on hits around 13.4 volts and 13.95 volts AC off. Mission accomplished! This was a gradual issue over time, it kept getting lower and lower on the dash gauge. The AC load showed it up more.

mffarrell

Could you please post the part # for the voltage regulator?

Thanks!

dprantl

I already posted the one Bosch specifies as a replacement for the 996TT: https://rennlist.com/forums/996-turb...l#post14269190

Dan

Kevinmacd

Bought it from Pelican Parts Bosch. F 00M 144 136

mffarrell

Thanks!