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  #1  
Old 05-13-2017, 02:01 PM
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posulli88 posulli88 is offline
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Very High Voltage Reading After New Alternator

Just replaced/upgraded my alternator to a internally regulated 10si model from a late 70's chevy with same (I bought it new from rock auto).

This is the model: http://www.rockauto.com/en/moreinfo....1030217&jsn=13


My jeep is a 77 but I have the Z and M Engine harness that has the plugs for ac delco 10 si alternator. I just started the engine and am getting a ammeter reading in the red on the dash (almost to 60). Alternator is grounded to the engine block where the battery is ground. What would cause this? I have never used an ammeter so I am not sure how it should read.
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Last edited by posulli88 : 05-13-2017 at 03:07 PM.
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Old 05-13-2017, 03:35 PM
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If the external sensing wire that is supposed to connect to the battery post to sense the battery voltage is not connected, the alternator will crank out max charge because it thinks the battery is dead.
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Old 05-13-2017, 04:50 PM
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Awesome thank you fsjjunkie. I just checked my 2 wire (sense wire) and it is spliced into the fusable link that is connected to the battery positive wire at the solenoid. That should be regulating the alternator output correct?
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Old 05-14-2017, 06:28 PM
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Yes. The regulator in the alternator uses that sensing wire to tell what the battery voltage is and adjust the alternator's output accordingly. The higher the voltage is at that sensing line, the less output the alternator will have.

A proper functioning charging system should run at 13-15v depending on temperature. Higher voltage in colder weather. A typical spring day will probably be 14v or so.
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Old 05-14-2017, 09:13 PM
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serehill serehill is offline
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YUP

You're describing this as high voltage but referring to the ammeter as close to the 60 amps. The sensor wire should not go to the fusible link. One wire on the plug has power on it i all the time the one to the fuse link & the other needs to come from a source that is ignition switch controlled.
It could be as simple as the battery was close to dead which would naturally cause this, Check the actual voltage. Charge the battery & see if it still does it. If the alternator is overcharging the voltage will be high.

Info & wiring diagram,
http://www.route66hotrodhigh.com/Alternator.html
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Old 05-14-2017, 09:16 PM
Ristow Ristow is offline
 
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a delco SI that is working properly will not overcharge even with the sense wire disconnected.

it is common these days to get a junk alt right out of the box,however.

keep in mind,as rick said,you are looking at an amp gauge,and it could just be the battery was low and the alt is doing its job.
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Old 05-15-2017, 10:24 AM
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Need to check the voltage. The regulator should maintain 13-15v even with a dead battery, just current output will be really high.
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Old 05-19-2017, 09:03 PM
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Quote:
Originally Posted by Ristow
a delco SI that is working properly will not overcharge even with the sense wire disconnected.

it is common these days to get a junk alt right out of the box,however.

keep in mind,as rick said,you are looking at an amp gauge,and it could just be the battery was low and the alt is doing its job.

OR a bad batytery
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Holley 4180
Msd total multi spark.
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  #9  
Old 06-01-2017, 06:10 AM
rocklaurence rocklaurence is offline
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The amp gauge is reading Load. So, either the battery is really low or you have a heavy load on something else. If it continues, start pulling fuses to see what circuit is loading down [pulling amps] the system. Once you isolate the circuit then you can break it down to individual items [ie-bad light socket, failing starter solenoid]
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Old 06-01-2017, 08:08 AM
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Awesome Thanks everyone. Ended up being my battery, it was pretty low. Charged it out of the vehicle and started it back up and the ammeter read normally. Should be good to go now.
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