Is this my alternator?

Factual Questions
1

Car died yesterday. Luckily, I was at mile 49 1/2 of a 50 mile journey home, so I just ditched it on a side street and walked the half-mile home.

Some brief car history: Bought the car in December; 140,000 miles, Nissan Stanza, no problems with it yet. It looks to me like the alternator in there is relatively new. At least it doesn’t look like the original alternator.

Anyhow, about three weeks ago my battery died. I had left a door open or something and the door light killed the battery (I guess). I hadn’t driven the car in two or three days so I don’t know when the battery died. I decided to just buy a new battery, as I have no idea how old the battery in the car was.

So, we have new battery. Yesterday afternoon, I had a new car stereo installed. I don’t know whether the electrical work involved here could have led to my problem, but I’m just putting it out there in the interest of full disclosure.

Last night, I’m on I-55 at Cicero, when I realize that my interior lights are awfully dim and that the car isn’t responding when I hit the throttle. It starts misfiring. I turn off my radio, throw it into neutral, and make my way onto the off ramp. Once I get to the street, the car’s dead. I turn off the car, and turn it on, nothing. Save for a brief grunt and the click click click of the starter.

I and a stranger on the street push it over to the gas station. We jump the car, the car starts, and I jet off. Four block later it dies again, by another gas station.
One of my batter cables is a little loose, but I’m still getting current from it. I secure it a little more tightly and jump the car again. It starts. I get about another four blocks before it fails again. Luckily, right by another gas station. One more jump, and this time the car has some difficulty being jumped, and only gets about two blocks down the street before I give up this silly game.

Other data points to consider: The battery light never came on on the dashboard. No emergency lights appeared at all until the engine cut out. The final time the battery died, there was no sound at all from the engine. The headlights still worked, as well as the interior lights. (This is unlike when I replaced the battery; that time all the electronics were completely dead.)

So what’s the verdict? Or what further questions need I address?

2

It sounds like an alternator. The fact that the battery wasn’t drained just means that it wasn’t recharging. There’s still enough juice to run the lights, so it’s not the battery.

Alternators are cheap and easy to replace, but make sure that you get one from a reputable place. Pep Boys cannot be counted among them. Their remanned alternators suck. Chances are you’ll go through a few of them before you get a good one. I’ve never, ever gotten a good one right from the get-go, it always required a second trip at the minimum, and usually a fight.

3

Other than the almost dead battery, is there a way I can check for sure whether the alternator is functional or not? Like using a voltmeter or something?

4

A voltmeter can only indicate voltage, not wherether one or more of the rectifier diodes are toast and allowing a crappy waveform to be produced. Alternators produce AC power-the rectifier diodes are there to convert that sinusoidal voltage into near flat line DC, so if one or more of them are defective, the other automotive electronics won’t be happy. The small chain auto parts stores like Advance and Auto Zone will usually perform a free quick test of alternator output, checking voltage as well as the rectification.

5

Before spending the money on a new alternator, I’d take the battery cables completely off, clean them and the battery posts, and tighten them up real good when you put them back on. Then start the car and let it run for awhile and see if the battery charges.

A loose or dirty cable will affect everything else and make it look like the battery or alternator is bad. And if you don’t clean the cables, you won’t get anywhere by replacing the other parts.

6

It’s at least worth trying what cstamets said. My totally nonexpert opinion: it could be the alternator; it could be something else; but this

does make me suspicious.

7

It does me too. Except I have no idea how and why this would be a problem. I didn’t install it myself (installation was free), but I assume you just connect the wiring harness, and everything should be in the correct place. I suppose I could completely disconnect the radio and see if the battery charges then.

8

How powerful is this new car stereo you installed? If the car is drawing significantly more current than it used to, then it puts a much greater strain on the alternator. If it is a fairly high power stereo it’s going to keep killing alternators until you put in a more poweful alternator to match it. Someone who really knows a thing or two about electricity should check out all the wiring to make sure the wires are big enough to carry the current.

Don’t be too surprised if you end up replacing your new battery soon as well. When a battery gets discharged too much (usually because the alternator isn’t charging) then the battery can chemically self destruct inside.

If you turn the key to the “on” position but don’t start the car, the alternator light (may say gen or generator, or it may have some silly symbol that makes no sense until you look it up in the manual) will come on in most cars. I’m wondering if your indicator light is burnt out.

9

It’s the cheapest stereo with CD/MP3 capabilities I could find…200 watts (50W per channel). But if I keep it completely off, it shouldn’t be drawing a hard load, right? Well, I’ll start by cleaning the battery connectors and see what happens from there. Chances are, I’ll probably just take it into the shop and be done with it, but if it’s a fairly straightforward problem, I can take care of it myself.

10

If the radio does not have a seperate power amp, then it shouldn’t draw power if it is off. If you keep it off all the time though, why have the radio?

Hopefully it is something as simple as they forgot to reconnect the alternator after they were done mucking with the wiring.

If you have a voltmeter, read the voltage on the battery with the engine off, then again with the engine on, then maybe again with someone reving the engine (all the warnings about being careful around moving parts apply of course). The voltage should go up by about half a volt to a volt or so with the engine running, maybe a couple of volts with the engine reving. If it doesn’t, then either the connection between the alternator and the rest of the system is shot, or the alternator itself is shot.

There may be a fuse or a fusible link (a thin wire, acts like a fuse) in between the alternator and the battery. All you need to do is check continuity between the alternator and the battery, with the battery disconnected of course, since any current flowing is going to screw up your meter.

11

It could be something as simple as they disconnected the battery cable before installing the stereo (which I’m sure is probably a recommended thing to do) and didn’t tighten it up completely after finishing the installation.

Of course, it could be that your alternator is fried, but at least if you check the cables first, you’re not buying a new alternator for nothing.

12

Well, I would try this. Except that I can’t get the engine to turn. I went out to my car today, and it’s at the point that when I try jumping it, it barely tries to turn and all I here is starter clicking.

I’ve got another battery (the old one) in the garage being charged up. I could hopefully try this tomorrow when the battery is charged (or almost charged). I’ll swap the batteries and check the voltage.

I didn’t get a chance to go out there with my voltmeter, but when I plugged in one of those cigarette lighter jobs that are supposed to tell you your battery and alternator power it didn’t register any charge at all. When I apply the jumper cables, I can get enough power to work the headlights, intererior lights, and starter, but that’s about it. Not enough to turn over the engine. When I try turning it, the engine goes for maybe one second before it gives up. When I remove the jumper cables, there’s still enough charge to keep those low wattage devices going, but nothing else.

13

Oh great. And to add more possibilities…I checked the water level of the new battery and they seem really low to me. I mean, there’s still water in the battery, but it’s nowhere near where it should be. Shoulda checked that before I installed the battery.

14

I replaced a battery s few years ago and assumed that the electrolyte level in a brand new battery would be as it should be.

Car wouldn’t start a couple of days later, took the battery back for them to check and it was wrecked, they had forgotten to add distilled water before selling it, plates had warped. You may be experiencing something similar.