328 Battery not getting charged

Without verifying, I believe the alternator is working properly since once the car starts she'll run and run all electrical systems w.out compromise. Have replaced w.new fully charged battery and it just gets drained, no charge from alt.

Is there a solenoid or relay that's packed up and not allowing juice back to the battery?

How can I check w.a meter? I'm getting about 2.5V across terminals (disconnected from battery), and 13.2V across batt posts.

Thanks.

 

No, but that's what I was thinking - where is that? Best info I can tell to drain is on a 30-60mi highway drive she's done.

ETA: Oh, is the isolator the red plastic 'strap' that plugs straight down?

 

I'm saying all systems run fine after start up until I drive it 30-60mi and shut it off. If I try to restart after that distance range, the battery is either too weak to start, or it's dead. If I jump it, she's good all over again - and will roll start if I don't have a jumper available - until I drive it another distance and shut it off.

I tested 12.5V engine off, key off, and 13.0 engine running idle and at 2K RPM. No change on the meter even to 3K RPM.

Before I got back to read replies here I unplugged the battery ground under the bonnett, 'cleaned' the already clean contacts therein, and then idled the car in driveway - high beams on, rad fan blowing a lot, radio on, heater fans blowing - with a full battery (per charger status meter 100%) 10min, drove immediately another 15', and idled another 10'. I was trying to hit the battery hard to see if she'd start again after that 35' drive with heavy electrical demand. She did, and with a soundingly strong battery.

Does that tell you anything?

 

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The red dashboard charging light extinguishing at 3K RPM doesn't necessarily indicate the alt is working properly does it? There's been no change from previously normal operatin with that - lights at start, extinguishes at 3K RPM.

Have not, but will try this evening if I get a few minutes.

Right - should've thought of that considering I've replaced two RRs on my Ducatis, though symptoms differed.

What meter tests can I run to determine if the problem lies in the reg or if lies in the alt?

 

So you're saying I need to just pull the alt either way since it's pretty certain the prob is the alt or reg? Haven't looked at it in vivo yet but the diagram looked like the reg might be solely removable w.out removing the alt. I'm inclined to just order the reg (121840 V/REG. 80A ALT. 308/328) and try replacing. Last time I sent something in for a bench test (speedo to PAS) all I did was add $75 overnight freight and $150 bench test fee to my resolution which was unrelated to the speedo!

 

Thanks for the pic Steve, helps a lot.

Of course this condition developed this past weekend ahead of the car's debut in a Southampton wedding. I have two jumper packs safely 80mi away from the event and had to buy a 3rd at the only autoparts shop in town - no time to go the 8mi (30' one way on a sunny summer Hampton weekend) to Wallyworld. Poor groom was stressed enough w.out me having to drop the casual warning as he escorted his bride to their flashy red chariot, "BTW don't botch the startup now, you have one shot at it. And don't stall it out - if you DO stall, make sure you're rolling enough for a roll start."

 

Follow up: alt is off to the rebuilder today.

Thanks for your replies gents.