help on battery problem - dead alternator?

[darconi]

Appreciate any help anyone can provide on this.

I've been having this problem where my battery has been discharging/dying while driving. If I leave the battery connected and the car off, it pulls power like normal but once the car is on and I start driving for a while, it discharges rapidly. I'm estimating somewhere around 20-30 mins of driving for entire battery to be discharged from full. The battery checks out fine and has been recharged using chargers.

I got a battery voltage monitor that hooks into the lighter and it constantly tells me the voltage.

Once the car is on, the initial voltage starts at approx 13.5-14 V (which is normal for recharging I believe). However, it quickly over the next few minutes drop down considerably. After ~2-3 minutes, the recharge voltage enters the 12.5-13 range (and the monitor gives me a red warning). After another 5 minutes or so, it can be around 11.5-12.5 range and so on.

I'm guessing this indicates my battery is not being recharged and the only thing I can think of is alternator is not working. I did take it to autozone once and they said the alternator is fine but not sure I believe them.

I did had to replace the ignition switch before (thanks to renntech), is it possible I didn't install it right and its draining cause of that?

Would appreciate any help/suggestions. Is this something I can take to any mechanic or should I contact a porsche speciality shop?

Thanks!

[RFM]

I would suspect the voltage regulator ( build in alternator ). Let check the alternator again during at least 30 minutes under load, try to create the same conditions as you have experienced while driving.

[darconi]

I would suspect the voltage regulator ( build in alternator ). Let check the alternator again during at least 30 minutes under load, try to create the same conditions as you have experienced while driving.

If I did that and it is the voltage regulator, what should I expect?

[RFM]

If it is the voltage regulator, you can (let) replace the regulator for a couple of $, and do the test again.