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I upgraded the 55 amp 10-SI alternator in my '65 to a 96 amp 12-SI. I also installed an aftermarket voltmeter and disconnected the factory ammeter. When I start the car, the voltmeter shows about 11 volts and the lights are dim and they stay that way unless I rev the engine to get the tach up close to 3,000 rpm, then the lights get bright and the voltmeter reads close to 14. Once it gets there, it stays there and everything runs fine, even at low rpm. I did not change any of the wiring to the alternator. Does anyone have any ideas about why this happens and how to correct it?
 

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All alternators have a different "turn on" RPM. It is impossible to get 2 exactly the same. You could try switching to a smaller alternator pulley to to lower the engine turn on RPM.
 

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Alternator isn't working. The 14 volt reading is too low. What are you reading on the 2 alternator connector pins at idle. Measure each pin to ground and post back.
 

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John - not to doubt you, because from what I've seen - you're always right. But, it just sounds like the excitor on the alternator isn't firing until it hits 3000 or so RPM.

Is 14 volts really too low? I've got a 170 amp Powermaster that puts out a pretty steady 14.4 volts, and I thought that was acceptable.
 

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Originally posted by SNFU Mobile:
John - not to doubt you, because from what I've seen - you're always right. But, it just sounds like the excitor on the alternator isn't firing until it hits 3000 or so RPM.

Is 14 volts really too low? I've got a 170 amp Powermaster that puts out a pretty steady 14.4 volts, and I thought that was acceptable.
LOL. I'm hardly right all the time. There's usually quite a few guys visiting this forum who have more information than me.
Yes, it does sound like that to me but one shouldn't have to mess around after buying an alternator. Spend your money you should get a working product.
That 96 amp sounds like the one used on 80s GM cars with a 3.8 and air conditioning. They should put out a good 14.5 volts at a normal idle. His isn't getting there even at 3000 RPM. Just checking to see if it could be something else.
Your alternator sounds fine.
 

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Anything over 12.6-12.7 volts indicates a working alternator. Maybe not great but working. The battery is not able to maintain any voltage higher than that on it's own. Like I said the "turn on" RPM is too low. Maybe when the alternator was changed it came with a larger diameter pulley on it. That would slow down the alt. RPM causing the engine to have to spin faster to get same alt RPM as before. Does that make sense? I'm couting on John to keep this going to at least page 2.
 

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OK, I'll streach the page. Yes, if it's above 12.6 is working, but it won't charge the battery.
 

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So a volt meter (voltometer?) measures how many volts the alternator is producing, while an amp meter (ammeter?) measures how much current is being drawn by devices on the circuit? Do you need both on your car (would it be better with both)? I remember seeing something about Shai's car almost getting cooked by the ammeter. What was that all about? Are the factory ammeters junk? Should I get rid of mine? Are we on page two yet?
 

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Cecil, ammeter measures either draw on electrical system or how much alternator is putting out. Ammeter's not nessesary in the car, more for diagnostics. A simple volt gauge is all that is needed.
 

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If you have the volt meter connected to the fuse block, that would account for the lower reading. 14.7 is at the alt output..7 volts is not much of a drop from the alt output to the fuse block. Do you have the dash indicating light connected? If not you need to rev the engine get the alternator to self excite.
 

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Boy, sure got a lot of miles out of this question. Now if John M. would just give us his answer. But, maybe I'm just some nobody with an old faded paint, ragged landau, and otherwise doggy L35/M20 on the build sheet, so I just don't rate, eh??? Guess I better look around for an L78/M22. Would that maybe get you to tell me how YOU would hook up a 3 wire alternator JM????? Thanks for nuthin' so far.
 

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7 volts is a HUGE drop from alternator to fuse block. If you had more than 1 volt drop from the headlights to the taillights you have a problem. There should be no more than about .4-.6 volt drop from the alt to the fuse block. There will be more because the wiring the is 30+ years old and a poorly designed electrical system to begin with, but A half a volt is about max.
 

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First off, considering that a voltmeter guage isn't super accurate and where it's connected reading 14V with it seems fine to me. Also, Elree said a 0.7V drop, not 7V.

Secondly, is this a 1-wire alternator? If so then what you are seeing is normal. If it's not a 1-wire then I'd suspect that the alternator light isn't connected.

Thirdly, There really isn't anything wrong with the factory ammeter. It is the aftermarket ammeters that often cause problems because you have to run the main power wire into the passenger compartment to the meter. Short out that wire and your car can burn. A factory ammeter just reads the voltage drop across a piece of wire in the main harness between the battery and the horn relay. You can reconnect it and if you still don't feel safe put 1A fuses in the wires.

Lastly, the alternator upgrade link on this site was posted 2X Byrddude. Maybe try looking there.
People here have no obligation to help you.

Peter
 

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Originally posted by Byrddude:
Boy, sure got a lot of miles out of this question. Now if John M. would just give us his answer. But, maybe I'm just some nobody with an old faded paint, ragged landau, and otherwise doggy L35/M20 on the build sheet, so I just don't rate, eh??? Guess I better look around for an L78/M22. Would that maybe get you to tell me how YOU would hook up a 3 wire alternator JM????? Thanks for nuthin' so far.
Let's see. Peter told you, then Mike told you. Here it is again. You just need to read. Keep saying I'm not the only one around. Only one of the noisiest.

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

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Discussion Starter #17
I'm back guys. Thanks for all of the great input. I didn't have time last night to test the output at the alternator, but I did read all of the posts to this question and I have some additional information. This is a 3 wire alternator and my car does NOT have an indicator light at all, the wire to the factory ammeter is cut and capped. The Voltmeter is connected at the fuse panel.

Based on some of the feedback, it sounds like I need to install some kind of indicator light (on the wire that used to go to the ammeter) to excite the alternator. Is this right? What kind of indicator light should I install and where can I get one?

Thanks again for all of the great responses.
 

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I have the same question. All I want to do is hook up a CS130 3 wire alternator without a light in the factory circuit. I will use what ever I need to excite.... arouse ...envigorate or whatever the damn alternator, Seems someone should be able to define this task clearly and precisely.

The archive section (Wes Van ) published a large note on this very topic and it helps a lot. Even Wes says someplace the CS and the Si are the same as far as connections for the exciter circuit /arousal light whate ever it is. So I guess that would be all you need to read. Wess shows how to bypass the regualtor on the rad support and everything. Seems like a freakin piece of cake. The document should be required reading for anyone trying this upgrade. I THINK it covers everything that is needed but every time I read one of these posts I get a little twitch in my gut that possibly just possibly I have missed something.

The trouble with electronics is that there can be more than one way to skin a cat (wire a CS130) that is why I did not enrole in electrical engineering and chose mechanical instead. At leaset with mechanical devices ya can see the device / mechanism. With electronics sometimes all ya see, if you are lucky, is a puff of smoke. Sometimes nothing is seen but but components are none the less fried.

Guys I recommend reading Wes Van's article very carefully at least once. Look at the MAD Electronics site also...www.madelectronics.com they have a bunch of diagrams and tech papers about the circuits on these cars. Again VERY VERY helpful. Not all answers for all folks but give it a try.
 

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On the origional regulator connector there was a brown wire going to therminal #4. This is the wire that should go to the #1 terminal on the alternator regardless of the car having a light or not. If the car doesn't have a light there is still a resistor in that wire. The alternator wiring doesn't require the ammeter to be wired and is seperate to the ammeter.

Oman, I believe the alternator requires about 25 to 50 ohms of resistance going to the terminal in place of the bulb. In reality, there is a resistor in parallel to the bulb from the factory so if the bulb fails the alternator still gets current so it will start to charge. I've never measured the resistor in the factory harness though. Use a 10 watt resistor. You could just get away with a 5W if you use 50 ohms.

Peter
 

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Peter

Thanks again. I have a site for a CS130 install into these cars ...I will post but I don't have it in front of me know. Hopefully somebody will actually read it!? I think a lot of the confusion surrounds this darn excitation issue and the CS130 site (like a lot of these discussions) does not really address the isiot light issue.

Will post later today.
Oman

PS can there be a voltmeter as the resistance in that circuit instead of the bulb? Right now I want a Voltmeter or Ammeter someplace in my system (I like the Voltmeter idea better due to safety issues) so if I gotta put a bulb in there anyway why not a guage? It will provide resistance and that seems to be the key to excitation / arousal right?
 
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