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1971 Deville
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22 Posts
Discussion Starter #1
For some reason the alternator on the Caddy is not charging the battery so we got a new one after we had the old one checked and it showed it was good.......yes we did. After placing the new alternator on the car we checked with a volt meter and it did not appear the alternator was not charging the battery. My question is should the volt meter show 12.XX when the engine is on? I am not going to believe we have 2 bad alternators but for some reason they do not appear to be charging the battery. how can we confirm this? We have the positive connection going to the battery as well as the negative. Any help would be appreciated.
 

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1970 Coupe De Ville//Cessna 172
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551 Posts
Regulator? Wiring?
Do you have an alternator idiot light when the key is on but not running? The bulb needs to work to complete the circuit
Jeff
 

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1971 Deville
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22 Posts
Discussion Starter #3
yes, there is an idiot light and it is on. the clip for the idiot light is connected to the alternator. From what I understand the voltage regulator is now internal so the light may stay on. I have heard the engine has to be around 3k rpm for the alternator to charge. We are looking at a voltmeter while the engine is running and it shows 12.xx we will try to get the rpm up to around 3k and see if anything changes. we probably really need to get this thing on the highway and run it for a while but want to see if we can tell if the alt is working before we do that.
 

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2003 Deville base, 69 Eldorado, 68 Impala, If I tell you the rest......well....
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492 Posts
At idle it should be 14v, no need to rev it to 3000. Make sure what kind of alt you got internal alt or external. If it's internal make sure you have good grounds alt to block scrap any paint off alt.
 

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1971 Deville
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22 Posts
Discussion Starter #5
so the ground needs to be to the block and not to the neg? I did notice it was a bit loose and we will tighten it up and check again. I am not sure what you are referring to regarding internal or external but guessing voltage regulator. I am guessing it would be internal.
 

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2003 Deville base, 69 Eldorado, 68 Impala, If I tell you the rest......well....
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492 Posts
If i'm correct, all the wires you have connected to the alt is, one to + on battery and one to -? All you need is one wire to the positive on the battery, the alt is grounded to the motor make sure it is metal to metal, scrape paint off alt that contacts motor. There are wiring kits out there so you can connect your dash light. Don't guess you need to know if you have a internal or external regulated alternator, what is the part# and brand so we can verify for you.
 

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1970 Eldorado.
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4,023 Posts
We had some more posts with similar problem over time. Please clean your battery poles and battery connectors. Scrape them completely clean and grease them with battery grease or vaseline.
 
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