Alternator or battery failure??

VaSteve · 02-10-2008, 05:01 PM

First a couple of weird foreshadowing things:

1. This morning I was tossing some junk mail regarding Roadside assistance on the DD. Asked my wife about AAA membership renewal. She said she did.

2. While out on a drive today (like 20 min before the car died) I got thinking about an old Nissan I had where the alternator died. The warning signs were the radio failing, then the power windows then the car. I wondered what the signs would be on an old 911.

So after a good thrashing through the backroads, I was cruising along 66 on the way home. Next thing I know, my V1 makes a horrible noise and the lights are all off. So I shift my attention to the V1 and the radio starts crapping out. Only the back speakers work. Immediately, I think about the alternator from 20 mins prior. No lights are on. As I head for the side of the road I step on the brakes and the radio died completely. I shut her down to check the belts.

Belts are fine so I try to start the car again. No love. Call AAA. Then I tried tthe car again and it started. They advised me not to move it so the driver could find me. I fire up all the electronics (lights, etc) and let it run. Sure enough, the alt light came on a little, I think (hard to see with the sun) and the V1 acted up again, so I shut it down.

I was able to drive it onto the flatbed to avoid the winch tearing off my spoiler and up the driveway into the garage.

I tested the battery in the garage:
11.85 with the engine off (not good)
11.27 with the engine running (worse). (Didn't see the battery light on...garage was dark enough for that).
Light is not burned out...key turned to "on" lights both oil and battery.

I am assuming the alt died, but it seemed to give no warning like my Nissan did: flickering battery light.

So, what's next? I assume the alternator needs to come out to be rebuilt, new brushes or voltage regulator or something....bu which one.

FWIW, I did check (briefly) the trans ground strap. It appeared to be intact. There were a lot of broken branches out my way. I thought one might have knocked it loose.

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Additional data points... 30 min later I tested it again. Fired right up. Battery light was off in the car. Tested the voltage at the battery:
13.85v
Shut down the engine and tested again:
12.25v.
(mind you, this is CIS and it's cold as hell out there, so it's running around 2000 RPM). I let it run for about 3 min while I was testing this.

So what's the deal? Is actually my battery dying? I always thought you could run on a dead battery assuming the charging system was OK. I'd rather replace the battery than the alternator, but actual diagnosis is not my strong point.

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I'm suspecting the battery now... Just checked voltage on the battery again...12.02v. Seems to be losing its charge. It's fairly old (I've had the car 4 years and don't know how long it was installed before that). I've never had one die while I was driving. I guess we all gotta go sometime...but to fail suddenly with nothing being changed in the mix is weird.

Anyone have a guess?

dshepp806 · dshepp806's Garage

What exactly did the V1 tell you? Alarming for undervoltage? Over-voltage?

Best,

VaSteve · 02-10-2008, 05:54 PM

Quote:

Originally Posted by dshepp806

What exactly did the V1 tell you? Alarming for undervoltage? Over-voltage?

Best,

It beeped and made a funny symbol on the display...then went dark. That's what alerted me to pending issues.

Eagledriver · 02-10-2008, 07:25 PM

A bad battery shouldn't cause problems for you when the car is running. The alternator or voltage regulator is failing and causing a low voltage condition. I think the 83 SC has an alternator with an integrated voltage regulator so when you replace one, you automatically replace the other.

-Andy

tsuter · 02-10-2008, 09:58 PM

Put the battery on a charger overnite then take it (not the car) over to your local Batteries Plus and have them load test it.
Report back......

rick-l · 02-10-2008, 10:10 PM

Are #1 and #2 in your just random thoughts and not triggered by any symptoms in the car lately?

Did the car just all of a sudden die with no previous symptoms?

Sounds like the battery internals disintegrated with a set of plates that shorts and opens. An Autozone load test will answer that for sure.

IROC · IROC's Garage

Even though it does sound like the alternator, I would follow the advice to get the battery load tested first. I've wasted time and money before troubleshooting electrical charging/starting problems only to find out in the end that the battery had a dead cell.

It would also pay to check the ground cable and positive cable for any obvious signs of something amiss.

VaSteve · 02-11-2008, 04:51 AM

The battery is being tested now. I think that might be the cause. The install stickers are from 1999! I mean come on, a 9 year old battery owes me more than this!!

Formerly Steve Wilkinson · 02-11-2008, 05:51 AM

I just went through all sorts of contortions on our relatively new Boxster (2004) which was dying in hours, not just overnight. Even went so far as to make a service appointment, which I rarely do, because I couldn't figore out what the cause of the problem was.

Turned out to be a seriously bad battery, which, thankfully, I discovered before undergoing the embarrassment of taking it to the dealer.

Modern Porsche batteries, by the way, are turning out to be terrible. I'm told by the local independent Porsche shop that they're typically three-year batteries and should be replaced with good Interstates.

hytem · 02-11-2008, 06:40 AM

Quote:

Originally Posted by Formerly Steve Wilkinson

I just went through all sorts of contortions on our relatively new Boxster (2004) which was dying in hours, not just overnight. Even went so far as to make a service appointment, which I rarely do, because I couldn't figore out what the cause of the problem was.

Turned out to be a seriously bad battery, which, thankfully, I discovered before undergoing the embarrassment of taking it to the dealer.

Modern Porsche batteries, by the way, are turning out to be terrible. I'm told by the local independent Porsche shop that they're typically three-year batteries and should be replaced with good Interstates.

Just replaced the OE battery in my Boxster with an Autozone 48. Maintenance free. perfect fit. 3.5 years and 37K miles on the old battery. The Autozone was cheaper ($86. with exchange) than the Interstate.

I had the alternator go dead in my old Z3, after replacing the battery at a BMW dealership. The dealership missed the bad alternator(!) I had to jump start the car with the new battery. That was the clue. The car died on the way to the dealer. That is scary. I have never had much luck servicing at BMW dealerships.

slw911SC · 02-11-2008, 12:12 PM

Darn electrical gremlins! I just went through all the battery/ alternator/ coil/relay/short/grounding etc. trail on both my 83 SC, and 98 Volvo S70. Both times, although the difficulties were showing symptoms of a bad alternator, it turned out to be a bad battery cell on both cars. I replaced them, and no recurring problems so far.

"Simple is Successful" - Jackie Stewart

Cheers,
Steve in the Frozen North