Electricity - my worst nightmare

[rbonnett]

This is on the SIII - so neg. earth and alternator. The back story: Saturday I left the lights on overnight, so the battery was totally flat Sunday morning. I used one of those jump start boxes to get it running, drove around for about 15 minutes and left it idling for another 15 or so.
This morning, just enough juice to click the solenoid so I figure I didn't let it charge enough the day before. Used the jump start again, got running and headed in to work. After about 30 minutes or so of running fine, I was idling at a light and it just stopped running.

I tried the jumper box again, but nothing this time. Its acting like the battery is completely flat: not even a dim glow from the lights, etc. Acts the same with the jumper box giving it juice.

My first thought is my who knows how old battery has given up the ghost. I've heard tales of those jumper boxes damaging older batteries. Other than that, any ideas what else it could be? I know it could be a short of some kind somewhere else, but that seems like an awful coincidence in timing if it is. Is there anything about the alternator that could cause this? It seems like even if the alt was dead, having juice from the jumper would at least work the lights.

Thanks as always

[amcordo]

Most likely your battery got damaged when it bottomed out and needs replaced. If it was running ok at higher revs then perhaps the alternator was powering the vehicle.

That being said it's always possible that something further down the line got damaged by the low-power (the voltage regulator maybe? I've never opened it up to study it). Electronics don't like brown-outs.

[Nium]

If the battery isn't a no-maintenace battery you should check the electrolyte levels in the cells because after 30 minutes of running the battery should have been completely recharged. If the levels are low be sure to fill to max level with water (preferably distilled or purified). If anyone ever put an in-line fuse in the wire from the alternator to the starter solenoid (hopefully no one did) make sure the fuse isn't blown or else your alternator will fry itself.

Likely you just need a new battery. Can always have just about any auto parts store check it for you.

[superstator]

Alternators need a little bit of voltage coming in to excite a field and generate power. Jumping a completely flat battery can leave you with a running engine, and just enough voltage to keep everything running, but not enough to actually let the system properly recharge - and I'm guessing that's what happened here. You actually had even a little less than that, as the battery eventually ran out of steam at that light.

Like amcordo and Nium said, it's new battery time. And a decent voltmeter can save a lot of heartbreak in these situations.

[rbonnett]

Just a quick update: I had the battery checked this AM - it was putting out almost 4 whole volts! New battery in - Rover runs just fine, at least for the first 10 miles. I'm going to take it in and have the alternator checked just to be sure.

[rbonnett]

Bearing in mind I am a novice when it comes to auto electrics...

The guy at the battery shop tested my alternator with a volt meter on the battery - said he thought the alt was shot. At idle he was seeing about 12.5 volts at the battery. Before I go out shopping for a new one, I want to sanity check this with you guys.

The charge light does behave as I expect - comes on when I switch the ignition on - goes out once the engine is idling - stays off while driving. Can this be working and the system still not charging properly?

On the way home I picked up a multi-meter and a Haynes book on electrics; looks like its time to learn this stuff. The book says to check the voltage at 2000 RPM or so, look for 14 to 15 volts.

In the morning I'll check this with my new meter, trace the wires in the charging system, make sure my fan belt is tensioned. If things look OK and I am getting 14-15 volts, can I safely assume the battery guy was just wrong? Are there any other alternator tests that should be done?

I'd hate to get stranded with a dead truck, so I'll be replacing the alt if it needs it, but I don't want to spend time and money if its not.

Thanks for the wisdom

[Nium]

The battery guy was incorrect at testing output voltage for the alternator at idle. You are correct in that the alternator needs to be spinning at about 2000 rpm to be putting out charging voltage.

At 2000 rpm you should be able to read about 14.5 V with the multimeter, set to test for DC voltage, at the battery terminals. When running the charge light will only illuminate if the alternator or battery is not functioning correctly. Thus if it stays off while running it's a pretty good indication alt is ok.

Here's a good web page explaining the charging light and alternator wiring...
http://www.alternatorparts.com/understanding_alternators.htm

[rbonnett]

In the course of everything else I noticed my belt was getting worn so I tried to replace it today and broke the case of my alternator :eek: In fairness I suspect it was already cracked, I doubt I'm that strong. Pictures attached. Doesn't seem like something that can be fixed, so its time for a new one.

RN has a Pro Line that looks like it will plug right in - but that means waiting til Monday to order and mid-week to get it here. Does anyone know if the Delco replacements, 10 or 12 SI will install with the factory mount? Also, from the pics of the Delco I have seen the wiring plug looks completely different from the one on my broken Lucas.

Thanks.

[BackInA88]

Or you could take advantage of the free shipping offer on weekends and order it through the web site.
I don't know if they will accept yours as a core since it broke but I suspect they might.

Steve

[siiirhd88]

The Delco alternators will not directly fit on the Series mount. The mounting boss on the Delco is narrower than the two ears on the Series alt, and uses a 3/8" diameter bolt. You will have to add a spacer or washers and you might need a double belt pully just to get the belt to line up. You can sleeve the inside of the Delco boss to use a 5/16" bolt, or drill out the Series mount to use a 3/8" inch bolt. If you intend to use a Delco alt I recommend an aftermarket mount from Ike at Pangolin, or a R. Davis mount.

You can use your existing wiring with a Delco alt, but you will need to change the wire ends.

Bob

[rbonnett]

My new Pro Line alt. showed up today - it has a strangely asymmetrical cooling fan. Pic attached. Does this look right?

[Nium]

Probably should give RN a call just to make sure. That looks like a manufacturing defect, but it wouldn't be the last time I was wrong.