Is my alternator draining my battery?

[Axle Roads]

Could someone please tell me, which leads coming off an alternator should be showing a connection to ground (Neg Bat post)? I'm using a multimeter to track down a possible short in my wiring. After I remembered to close the car door, I've narrowed it down to the alternator. It's a three wire alternator and all three are showing a connection to ground (car's off, ground lead still attaches). There's no power going to lead #1 so I don't understand why the alternator would be acting like this. Is this normal or should I investigate further?

It's not stock for my '67 mustang 200. It's one of those 10Si series (Internal regulator) that Mark at MadElectrical recommends. From a 1975 Oldsmobile 350. Part # 7127-3/M3. It was putting out 14.8 volts last time I checked, which was a few weeks ago.

Here's a pic. http://i3.ebayimg.com/05/i/001/15/c9/e6a0_1.JPG

 

[CoupeBoy]

Most simple way to find a draw on the system would be to
1. losen the positive battery cable
2. use a test light to make a connection between the newly disconnected battery cable and the terminal, it should light up
3. unhook the power to devices on your car, one at a time until the light goes out, also note if the light dims as you may have more then one source of draw on the system.

In your case, I'd remove the connections to the alternator one at a time (leaving them disconnected) and see if the light goes off after any or all of them are disconnected. If yes then the information you seek may be useful, if no, then your problem is elsewhere and you will need to keep searching. Since your alternator is non-stock the best location for information would be wherever you bought the alternator, or if you used a website to complete the conversion it should have a wiring diagram.

If you have any aftermarket radio with built in clock you should start with removing the fuse that always has power, as it will keep your test light on.

For the rest of the devices in the car you should start with one fuse at a time, this is easiest done with a helper, one to pull fuses, one to watch the light.

good luck
-ron

 

[Axle Roads]

Okay. I did as your suggested, but using a multimeter instead of a test light. The short is coming from wire #2. That's the Control Voltage Input (sensing) lead on my alternator. On our cars I think it would equate to A+ on the voltage regulator. As seen here. http://www.blert.net/comet/i/gen2alt/GENERATOR.jpg Can Someone help me understand what might have gone wrong inside the voltage regulator/ alternator. I'm looking at a diagram here: http://www.alternatorparts.com/altfig5.jpg

I bought the alternator for 10 bucks plus shipping on eBay. If it's just a bad diode I might be able to take it apart and replace it with something I have laying around. I also have the old external regulator still in the engine compartment. Does anyone know if I could use that to mediate the short (control the internal regulator)?.

 

[Stubby]

I did the GM alt swap and the wire diagram I used had the two wires switched.
IIRC, everything worked well but it would slowly drain the battery. Switched the two wires and all is well.

 

[Axle Roads]

I think that wiring diagram is still on the web fooling people, lol. A few weeks ago, I had to guess and verity to see which was the field and which was the sensor. I measured voltage at the main junction, using a multimeter and switched leads #1 and #2 back and forth. In one configuration I measured 12.6 volts and in the other I measured 14.8. I settled on lead #1 going the junction black for remote sensing and and lead #1 going to a home fabricated indicator light for switched power and field activation. Please correct me if I'm wrong.

I never considered the possibility of a slow drain on my battery using the wrong configuration. Since the swap, I've noticed improved performance with a fully charged battery and a slowly decrease in performance at WOT or under stress (like hills and on-ramps). I didn't even notice the battery drain since I often put my battery on a slow charger after working on my car with the doors open. The only thing I could think of was perhaps I switched 12v IN with Switched ON/OFF at my ignition relay. Today while checking the relay and labeling each wire. I accidentally noticed a curious conductivity pattern which would suggest a short somewhere.

Now, if my internal regulator was switched on this whole time (about four weeks) I would have run a good chance of wearing something out. What would that be? What happens to a voltage regulator which is allowed to remain on too long?

 

[Axle Roads]

So, I'm just guessing my internal regulator died. How can I know for sure?

 

[CoupeBoy]

Pull it off the car, take it to a parts store and have them test it, the machine checks for charge output as well as diode operation. Of course they will try to sell you a new one but if you feel comfortable buying the 'Help' kit to repair the alt, go for it.

-ron

 

[Axle Roads]

I thought I needed a current under a load test, not a simple volt test. So here's what I did. I removed the 10si today. I had found an extra 12si in my garage. I got the 12 SI tested at pep boys. It passed, measuring 15.23 volts.

Great. That's almost three percent higher than my 10si. I installed the12 SI, but here's the thing, lead #2 is still appears to be drawling 12 volts from the battery. Now, I don't know what to do next. Should I just add a relay switch.

My mustang doesn't use a horn relay. Could that be the problem?

 

[CoupeBoy]

I'll check my old tractor, I think the CoOp has a 10si on it. I'm going to go by the instructions found
http://www.antiquetractorstore.com/arti ... int195.htm

I'll let you know what I find, once I get time and the weather cooperates, we are expecting 3-5" snow today and up to 15" in some locallized pockets by the end of tomorrow.

And now I'm wondering if the alternator setup on my IH856 doesn't have this type of alternator. However if it does have this setup I've got other issues sine it also has a voltage regulator under the steering column, which might explain why it never charges...

-ron

 

[Axle Roads]

Weather's turning a corner here and so is this mystery. You can scratch my last post, the 12si passes the light test after all. While following your instructions above. I substituted a voltmeter for a test light. That was a mistake. While newer 12si lead #2 will set off the volt meeter at the battery post, it wont set off a 12 volt bulb. I had to check it a few times to believe it. I think that means there's a potential charge but insignificant current. In other words, I got schooled.

To know if my original problem is fixed, I will either swap the10si back in and conduct further tests or drive the 12si around. Driving with the 12si sounds like more fun.

 

[Axle Roads]

Thanks. I found no drain in either the 10si or 12si alternator using a simple 12v bulb test. I finally drove the car today with my 12si. The alternator indicator light goes out completely, unlike the 10si which dims with revs and stays dimly lit (I didn't yet trust the light since I recently built it myself from scratch). I'm thinking it was the bushings not the diodes. Regardless, I have a working vehicle again using the 12si thanks to you guys. I wont know if this solves my original problem until I reach WOT, maybe tomorrow.