Alternator or voltage regulator? - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

 
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post #1 of 7 (permalink) Old 01-17-2016, 09:33 AM Thread Starter
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Cool Alternator or voltage regulator?

Good morning everyone. My Impala seems to want to use the battery to run on instead of the alternator. I have a full charge before I start driving but when I stop it's around 10 volts. If I drive more than 20 or 30 minutes sometimes it doesn't have enough charge to start. I've had the alternator checked and I've checked the charge on the battery while running and it's about 14 volts. Any suggestions? Thanks, AJ
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post #2 of 7 (permalink) Old 01-17-2016, 12:18 PM
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You didn't state what year Impala you have but since we tend to ignore W-body (wrong wheel drive with a six cylinder sitting side saddle), and other newer cars that bear the Impala logo here I assume you do not have a one wire CS alternator on your car.

When your car was designed there were no power drains except for the wipers and the lights. The alternator (or Generator if you have a 1962 or older car) was sized to provide 36 Amps at 12 volts which matched the Wattage draw of the lights. If you are driving in the rain with the lights on the total draw exceeds the power out put and the battery will start to drain (the Gen light begins to glow). Power windows and other power draws were handled by engine vacuum back when your car was new.

This worked well for the intended purpose of the car (daily computer or family car traveling in day light most of the time). It doesn't sit well with our current 24/7 world with us in constant touch with everyone else and always on the move (life was simpler back then though having lived through it I would have argued with you about it had you asked me back in 1963 when I was building my first hot rod). If you install a modern MP3 player (and radio or CD player or what ever else it does) it will require more power than the total out put of your alternator to power those 48 inch sub woofers and 120 dB speaker system.

To meet modern power needs (electric fans, electric fuel pump, electric powered windows and seat, stereo, and most importantly a constant voltage for the on board computers since most cars have 14 to 18 separate computers monitoring voltage sensitive senders) the factory has increased the smallest rated alternator that will still bolt in place of the case first used in 1963 from 36 Amps to 107 Amps. Almost all CS one wire alternators are at least 120 Amps with many available up to 178 Amps in the same size case (you can go to a higher rated amperage such as used on police cars and medium duty trucks, but it requires you to change the mounting brackets because the case is bigger to hold more wire in side the case).

The factory went from a generator to a 10 DN externally regulated alternator to the 10 DN with an internal transistorized voltage regulator (avoid these) to the 10SI series which where all internally regulated and most out put 63 Amps or more (the identifying characteristic is the field wired changed from being side by side to being parallel to each other), to the new CS and newer alternators that have the fan on the back of the case for better cooling.

MAD Electric is a very informative site if you have any automotive electrical questions such as why do might lights dim when I slow down, and a cure to these issues.

http://www.madelectrical.com/electri...elcoremy.shtml

Your best bet is to buy a one wire CS 120 Amp alternator and swap out the front pulley from a serpentine pulley over to your V-belt drive. It will then bolt up to your car. It is called a one wire as the only wire you need to connect is the now LARGER GAGE red wire from the alternator to the battery. You jump from your stock ten gage red wire to an eight gauge red wire because that is the size required to move 120 Amps five feet. If you need a longer wire than that I would go to a six gage wire. You then disconnect the wires going to the mechanical voltage regulator. You will tie two wires off (wire nut or wrap in tape to isolate them) and tie the other two wires together.

This site sells CS alternators with V-belts already installed:

http://www.speedwaymotors.com/Tech/e...onversion.html

This sister Team site explains how to rewire the existing mechanical points so that your Gen light still works:

http://www.chevelles.com/techref/ftecref14.html

Oh I almost forgot the advantage of the conversion is no more dimming head lights or lack of available power for any electrical accessories. A CS one wire produces 80 AMPs at idle (your DN doesn't produce it's full rated 36 Amps of power out put until the motor is spinning at 3,600 RPM; which is why the lights dim at idle).

Big Dave
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post #3 of 7 (permalink) Old 01-17-2016, 03:50 PM Thread Starter
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Thanks Big Dave. Sorry about the Impala year. It's a 1967 with the v belt pulleys. I put a 1972 sbc 400 in it with a 700R4. I used the existing wiring to hook up the alternator which is the large red wire and the two wire plug so that might be the wrong way. I'll go get a one wire and not use the plug. AJ
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post #4 of 7 (permalink) Old 01-17-2016, 03:54 PM Thread Starter
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Is there a minimum amp out put for the alternator that I should be looking for?
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post #5 of 7 (permalink) Old 01-17-2016, 04:28 PM
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Quote:
Originally Posted by Gear Geezer View Post
Thanks Big Dave. Sorry about the Impala year. It's a 1967 with the v belt pulleys. I put a 1972 sbc 400 in it with a 700R4. I used the existing wiring to hook up the alternator which is the large red wire and the two wire plug so that might be the wrong way. I'll go get a one wire and not use the plug. AJ
One wire only works with a CS style alternator (identified by the black plastic enclosed squirrel cage fan mounted on the front of the alternator. In 1970 GM was using the 63 Amp 10SI alternator or the dual pulley 12 SI on Cadillac, Buick and Olds cars rated at 72 Amps.


Here is a chart showing the out put of the alternator you currently have matched to engine RPM:

http://www.pirate4x4.com/tech/billav...curves_400.jpg

Here is some more history on the 10SI alternator you have now:
http://www.hemmings.com/hmn/stories/...feature30.html

You have to leave the blue and white field winding activator wires on your SI alternator or it will not charge. Only the one wire CS model is self exciting (it actually is wired into the ignition switch on newer cars with a four wire pin type plug so that it charges from start up; but if spun above 2,500 RPM even once without those wires attached it will charge from that point on until the engine is turned off).

Big Dave
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post #6 of 7 (permalink) Old 01-17-2016, 04:43 PM
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Originally Posted by Gear Geezer View Post
Is there a minimum amp out put for the alternator that I should be looking for?
That depends upon your electrical load Mike. If you want your lights to stay bright even at idle and to be able to drive more than thirty miles in the rain without draining the battery you might want to look at a higher rated alternator. The alternator case is stamped with the rated amperage on the back half usually close to the field winding plugs (but depending upon how the case is clocked it can be on any of the four quadrants, including the bottom inside were you can not see it).

This chart that I posted above shows the out put of a DN and SI style alternator. Both needed to be spun to cruise RPM to get to it's rated power out put.

http://www.pirate4x4.com/tech/billav...curves_400.jpg

As with all alternators they will not out put more power than needed so if everything is off except the ignition and your battery is fully charged it outputs next to no power and takes only the friction of the bearings and fan to spin it. As load increases the field coils receive more voltage exciting the alternator to out put more power to meet the load perceived by the voltage regulator. This is why if you have burnt points in the mechanical voltage regulator you can cook your battery.

People used to replace the points in their distributors every six to ten thousand miles but think the voltage regulator that is transmitting a much higher electrical load will last the life of the car. It doesn't!

The original transistors were terrible in the first series of internally regulated DN and SI alternators. They were prone to heat failure and any voltage spike would blow the rectifying bridge (such as jumping off the car). GM improved upon them and the materials that the transistors were made of improved with time to make them very reliable and consistent.

A CS style alternator hooked up to a 12 horse or bigger gas engine can actually be used to weld in the field. Now that is power!

Big Dave
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post #7 of 7 (permalink) Old 01-20-2016, 03:35 PM
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I have a CS130 105A. It puts out enough power to run 2 air compressors(air bags) and 1000W amp. along with everything else.
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