What Voltage Should My Alternator Be Putting Out? [Archive] - Chevelle Tech

: What Voltage Should My Alternator Be Putting Out?


adpostel
Apr 6th, 10, 10:15 PM
OK, I've been reading and reading. And I have rewired under my hood as described by Mark at MAD Electrical. I have a 94 amp internally regulated alternator (Ultima from Oreilly's) I have a 8 or 10 gauge wire going from the lug on the back of the alternator straight to my firewall mounted junction block. And I have the remote sensing wire from the internal regulator routed to this junction block as well. Everything else gets power from this junction block including my fuse panel and battery charging wire, which is run from the junction block to the positive lug of my remote solenoid. The theory is that I should be maintaining 14.2 or so volts to this junction block to provide an optimal amount of volts to all accesories. Well, it seems like everywhere I check voltage when the car is running I see 12.4 volts. I checked voltage at the alternator positive lug and 12.4 volts, then the junction block has 12.4 and the charging wire at the remote solenoid 12.4 and then at the battery 12.4. So it looks like the voltage is staying pretty stable, although my voltage meter inside is reading 12 volts flat. The only issue is that shouldn't all these voltage readings be at 14.2 volts? Am I missing something here? I mean everything is running fine, and I get a 12.6 volt reading from my battery when the car is off, but when I turn it on, I get a 12.4 volt reading from the alternator. Any help is greatly appreciated.

JIM
Apr 6th, 10, 10:29 PM
and battery charging wire, which is run from the junction block to the positive lug of my remote solenoid.

I'm not sure about that configuration, but yes, your alternator should be putting out at least 14 volts. What RPM are you testing it at? Some of the hi-amp alternators don't do squat at idle. Try revving the engine up to about 2000 RPM and see what you measure at the battery.

adpostel
Apr 6th, 10, 10:49 PM
OH, I checked everything at idle today. But even when I'm inside and giving it gas, I don't see the volt meter move at all? I mean it goes to 12 volts when I turn the key forward, and then it obviously drops a little during cranking, then when started, it goes straight to 12 volts and stays......

Greg Owens
Apr 6th, 10, 11:07 PM
That does not sound right. I get about 14.7 at the back of my alternator when I first crank it up. It drops a little when things get hot and the battery tops off.

Do Chevelles not use the junction at the horn relay buss bar? As long as your sense wire is at the same location I wouldn't think it matters but was curious.

novaderrik
Apr 6th, 10, 11:40 PM
every car that i've upgraded to a CS series alternator has put out 14.6 volts at the battery at idle with everything in the car turned on.
i always run a big cable directly from the big stud on the back of the alt directly to the + terminal on the battery, with no junction blocks getting in the way, then run a 10 or 12 gauge wire from the battery to a junction block to power the car. this is how GM started doing it in the mid 80's, and it works.

adpostel
Apr 7th, 10, 1:19 AM
So should I go swap that alternator out? I have a lifetime warranty on it, and it has literally less than 10 miles on it.

undee70ss
Apr 7th, 10, 2:56 AM
OK, I've been reading and reading. And I have rewired under my hood as described by Mark at MAD Electrical. I have a 94 amp internally regulated alternator (Ultima from Oreilly's) I have a 8 or 10 gauge wire going from the lug on the back of the alternator straight to my firewall mounted junction block. And I have the remote sensing wire from the internal regulator routed to this junction block as well.


Did you convert from a externally regulated alternator? Your voltage readings indicate no output from alternator. You describe how you have wired the alternators BAT terminal (output) and terminal 2 (sensing) but how do you have terminal 1 (excite) wired?

adpostel
Apr 7th, 10, 9:12 PM
My terminal 1 (excite) wire is wired to a keyed ignition source outlet on the fuse box. But I went ahead and took the alternator to Oreilly's to get checked, and what do you know, it was bad. FAILED, FAILED, FAILED on all tests. So I'm picking up another one tomorrow, of course they didn't have it in stock.

So now I am wondering what effects, if any, this had when my motor was running. In other words, would I have been getting a weak spark out of the dizzy? Would this have affected my performance at all? Man I've been going round and round tuning this motor, and I am wondering now if this is gonna change anything? Would this make my motor run rich, due to a low spark? I know its a lot of questions, but any help would be appreciated.

undee70ss
Apr 8th, 10, 4:13 AM
My terminal 1 (excite) wire is wired to a keyed ignition source outlet on the fuse box. But I went ahead and took the alternator to Oreilly's to get checked, and what do you know, it was bad. FAILED, FAILED, FAILED on all tests. So I'm picking up another one tomorrow, of course they didn't have it in stock.
Well, that most of the problem right there, you can not put a direct 12volt source to terminal 1, it has to have some resistance, either from the GEN light or a resistor wire. Factory idiot light cars have a GEN light with a resistor wire in parallel (to keep the alternator working if the GEN lamp burns out). Factory gauge cars only have the resistor wire. Personally, I would use the factory wiring for terminal 1. (brown wire that went to terminal 4 at external voltage regulator plug) If thats not possible, add a light bulb inline or a resistor.


Read the link below, its about a member on another board I helped who had his alternator wired like yours and went through several alternators, his was a CS130, but the principles are the same. Several solutions too.
http://www.camaros.net/forums/showthread.php?t=115803

So now I am wondering what effects, if any, this had when my motor was running. In other words, would I have been getting a weak spark out of the dizzy? Would this have affected my performance at all? Man I've been going round and round tuning this motor, and I am wondering now if this is gonna change anything? Would this make my motor run rich, due to a low spark? I know its a lot of questions, but any help would be appreciated.
Yes, it has some effect. As the battery runs down, voltage gets less and less.

adpostel
Apr 8th, 10, 4:32 AM
Personally, I would use the factory wiring for terminal 1. (brown wire that went to terminal 4 at external voltage regulator plug) If thats not possible, add a light bulb inline or a resistor.


So are you saying here that I could basically wire in a socket and a light and that would provide the "resistance" needed to make the alternator work properly?" Is NO RESISTANCE, burning out something in the alternator, possibly?



This is quoted from the MAD ELECTRICAL Tech Pages, which is where I got my diagram for my underhood wiring,

"The voltage regulator in the photo above is used with the Delco 10SI and 12SI alternators. Notice that the voltage regulator above has two flat blade male terminals (see arrows). There is actually a third terminal of this voltage regulator, which is the ground at one of the three mounting screws. One of the two flat blade terminals is wired to an ignition switched ON/OFF source, and this circuit can also be used to operate a dash mounted warning light (The warning light is an option, not a requirement).

Thanks for the responses, its definitely a learning curve with these electrical gremlins.......

undee70ss
Apr 8th, 10, 4:43 AM
So are you saying here that I could basically wire in a socket and a light and that would provide the "resistance" needed to make the alternator work properly?"
Yes. Use a 194 bulb. A spare old side marker light will work. i did this one myself once.

Is NO RESISTANCE, burning out something in the alternator, possibly?
Yes, the regulator.



This is quoted from the MAD ELECTRICAL Tech Pages, which is where I got my diagram for my underhood wiring,

"The voltage regulator in the photo above is used with the Delco 10SI and 12SI alternators. Notice that the voltage regulator above has two flat blade male terminals (see arrows). There is actually a third terminal of this voltage regulator, which is the ground at one of the three mounting screws. One of the two flat blade terminals is wired to an ignition switched ON/OFF source, and this circuit can also be used to operate a dash mounted warning light (The warning light is an option, not a requirement).

Thanks for the responses, its definitely a learning curve with these electrical gremlins.......

The light is only a option, (cars came with or without a light) but resistance is mandatory, unless you like replacing alternators often.

adpostel
Apr 8th, 10, 4:52 AM
This is getting very interesting. I followed the MAD Electrical site due to everyone recommending the site. I wonder why there isn't much information on that number 1 terminal other than what I posted.

undee70ss
Apr 8th, 10, 5:01 AM
This is getting very interesting. I followed the MAD Electrical site due to everyone recommending the site. I wonder why there isn't much information on that number 1 terminal other than what I posted.

Because probably most everyone is using the factory wiring when converting (which will have the needed resistance) and most conversion instuctions use the factory wiring, including the one I post. My best guesss.

http://www.chevelles.com/showroom/data/500/new_alternator_wiring_pic2.JPG

adpostel
Apr 8th, 10, 7:28 AM
OK, so I think I got it now. I will pick up my new alternator today, but since my underhood wiring isn't in stock form, it is in MAD Electrical form,(LOL),before I install it this time, I am going to take that exciter wire, and take it to a terminal on a spare light on my dash, the other terminal of that light will go to the keyed ignition source. This will be my idiot light, and I still have the volt meter. But an idiot light wouldn't hurt.

So basically, the exciter terminal on the internaly regulated alternator will always be "hot" when the alternator is charging. And when/if there is a problem, that terminal will go "negative" which in turn will light up my light on the dash, since now it will have a positive side from the fuse box, and the negative side at the alternator. Is this correct? And will this provide enough resistance to prevent burning out the new alternator? I think I'm getting this......

undee70ss
Apr 8th, 10, 2:30 PM
OK, so I think I got it now. I will pick up my new alternator today, but since my underhood wiring isn't in stock form, it is in MAD Electrical form,(LOL),before I install it this time, I am going to take that exciter wire, and take it to a terminal on a spare light on my dash, the other terminal of that light will go to the keyed ignition source. This will be my idiot light, and I still have the volt meter. But an idiot light wouldn't hurt.
Correct. The only difference from factory is you don't have the bypass wire (the resistor wire in parallel with the bulb) If the bulb burns out, the alternator will quit charging, but you will know this from the voltmeter. You can always carry a extra bulb. Some models of powermaster alterntors can be wired as a 1 wire or a 3 wire. They will still charge (acting as a 1 wire) when the is no connection (such as a bulb burning out) to terminal 1. This is a option also.

So basically, the exciter terminal on the internaly regulated alternator will always be "hot" when the alternator is charging. And when/if there is a problem, that terminal will go "negative" which in turn will light up my light on the dash, since now it will have a positive side from the fuse box, and the negative side at the alternator. Is this correct? And will this provide enough resistance to prevent burning out the new alternator? I think I'm getting this...... Correct, you got it. :D:D:D

JIM
Apr 8th, 10, 4:21 PM
Just thought I would throw in......
Greg, you are a wealth of valuable electrical info on this forum. :thumbsup:

adpostel
Apr 8th, 10, 9:05 PM
OK, we got fire in the hole! I picked up the new alternator 94 amp 12SI and while I was there, I was searching in the electrical section and found a 2-wire LED indicator light that was very small, and looked like it would provide for a nice clean install for an idiot light. It was about 8 bucks. To give you an idea about size, all I had to do was drill a 5/16 hole and the light just snapped right in. So I drilled the hole right above my Volt meter on my gauge panel, and wired it up as described above. Took all of 5 minutes, and it was like magic. When I turned my key forward, the light lit up and once started, the light went off. The car was a little cold, so it actually shut down on me while trying to idle, and the light came back on like clockwork. Turned the car back on, and the light went out. OH, and BTW, the voltmeter was right on at 14.2 volts. I went around and tested all points, and I was getting 14.4 volts at the alternator, at the junction block on the firewall, and at the battery. I will try to attach a pic of what the light looks like installed and the key forward. Thanks to Greg and everyone else for bringing this to my attention and I hope that this helps someone out in the future.

undee70ss
Apr 9th, 10, 1:22 AM
Keep us updated. Have never tried a LED light. I like where you installed it, right above the voltmeter.

undee70ss
Apr 9th, 10, 1:27 AM
Just thought I would throw in......
Greg, you are a wealth of valuable electrical info on this forum. :thumbsup:

Thanks for the complement. I just try my best when helping.

MTWilson
May 12th, 12, 2:31 AM
I know this is an old thread but I am planning to install a CS130 and want to use an LED as my warning light. But I thought the LED wouldn't provide sufficient resistance. Has anyone else done this. Does it work long term?

CoolBlueGlow
May 12th, 12, 11:56 AM
Just FWIW,

Note that a firewall mounted version of the electronic voltage regulator is available for those who want the stock appearance and wiring along with the benefit of electronic regulation of the alternator's field coil. With this approach, one can use one's stock (numbers matching) alternator and still get the substantial reliability and performance benefit of electronic voltage regulation.

The firewall mounted electronic regluator's mounting and electrical form factor is the same as the original relay type adjustable voltage regulator. These units are still easy to spot, however, because of minor cosmetic differences.(and because one's headlamps will not evidence flickering due to the constant opening and closing of the contacts in a mechanical regulator :-) Typically, the electronic firewall mounted regulator has a shallow, riveted cover, instead of the deep cover found on the OEM design.

These units run about fifteen to twenty dollars, depending on one's supplier.

If the cosmetic difference is unacceptable, and (s)he must have the absolute concours appearance of an OEM regulator housing, this is no large hurdle for a reasonably skilled restorer. With a very small amount of work, the electronic regulator IC itself can be easily adapted into an OEM housing, preserving the car's appearance and stock wiring harness. The wiring is exceedingly simple, and there is only one component inside the electronic regulator housing, typically a three pin ~14 volt fixed output voltage regulator in the TO-220 case style. I have observed that many of these do not feature heat sinks, though some do. Depending on the selected regulator, an heat sink may or may not be necessary.

Extremely handy individuals will skip buying and cannibalizing the aftermarket regulator (at $20.00ish). Instead they will go to Digikey or Mouser and order the regulator directly from them, at a cost of about $1.50 per unit. A typical example of an appropriate TO-220 cased regulator might be the PB137ACV, which outputs a fixed 13.7 reference voltage at better than 1A. Since the cost is so low, perhaps two or three of these units installed in parallel would be wise. For those who MUST tweak, it is exceedingly simple to select and install a variable regulator in the same TO-220 case package, who's output is adjustable via a trimmer pot. The LM317 is the classic model that comes to mind, though one should check the current limits on that, as I am flying without a net here. I believe the LM317 is a 1A device.

However one gets there, the externally mounted electronic voltage regulator will perform the very same electronic regulation of the alternator field coil assembly as the internal regulator in the typical late model alternator - while keeping the wiring appearance, harness, and function stock.

The cosmetic correctness issue may be important to some Chevelle enthusiasts.

Just my 2C

Keith
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