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Old 07-09-2013, 03:26 PM
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Delco 10SI alternator issues

I've been messing around with my alternator and getting frustrated. It's set up as a 2 wire right now. I had the 3 wire (using an idiot light) but when the key was turned on, the light didn't come on. The bulb was good because when I grounded the end that connects to #1 terminal, the bulb came on. My other problem is I have to rev the engine well over 3K rpm to "excite" the alternator. Regardless of what I do (changing pulley's etc) I still have to rev the heck out of the engine to excite the alternator. The alternator is chromed so I'm wondering if it's a ground issue? voltage regulator/ diode issue? Just looking for possible solutions or if anyone else has been there.

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Old 07-09-2013, 04:42 PM
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Sounds like the bulb is the incorrect one for starters.
The real issue may be the lack of a drop resisitor that was famous in the 10SI when it was assigned to do 63 amp duty. It is a drop resisitor that bridges across the regulator inside the alternator, to excite the alternator at low rpms, to remedy the xact type of problem you are having.
You do have power on the # 2 terminal with the key on...correct?
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Old 07-09-2013, 05:17 PM
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Originally Posted by LATECH View Post
Sounds like the bulb is the incorrect one for starters.
The real issue may be the lack of a drop resisitor that was famous in the 10SI when it was assigned to do 63 amp duty. It is a drop resisitor that bridges across the regulator inside the alternator, to excite the alternator at low rpms, to remedy the xact type of problem you are having.
You do have power on the # 2 terminal with the key on...correct?
I've disconnected the bulb completely. The #2 terminal has a jumper running to the Battery post on the rear of the alternator. The other is a 4 GA wire running from the Batt post of the alternator to the + side of the battery. So, if I replace the regulator, will this solve my low rpm excite issues?
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Old 07-09-2013, 07:22 PM
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Well maybe. My bet is that it needs the extra drop resistor in it. i will look for a photo of it to post.
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Old 07-09-2013, 07:39 PM
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Here is a picture. I hope it comes through. it is the only part labeled resistor.
IIRC anything smalle than a 55 amp model didnt use it.
If your has one in it, the regulator could be at fault.
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Old 07-09-2013, 09:31 PM
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I appreciate the info. I was messing with the alternator again tonight and decide to use a different idiot light. I turned the key on, nothing! instead of using the original connection on the alternator, I ran a separate wire for terminal #2 and 1. #1 being for the light. When I put the connection onto the prong for #1, the light came on. If I wiggled the connector for #1 slightly, the light would come on and off as I wiggled the terminal. I tried to start the car while the light came on and I revv'ed it to about 2K and the alternator excited! (so did I). I'm not sure what the problem is, but something is not right with terminal #1, so I may opt to purchase a new voltage regulator and see if that solves the problem. Getting close! Thanks for the help.
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Old 07-10-2013, 07:34 AM
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I don't use a light, mine is hooked to switched 12v, deleting the light altogeather...... works well
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Old 07-10-2013, 03:03 PM
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I don't use a light, mine is hooked to switched 12v, deleting the light altogeather...... works well
I had mine hooked up the same way. In this case, with the light, the light let me know terminal #1 is not making a connection somehow. If I ran it straight from a switched 12V, I would still assume #1 is working fine. It's weird, #1 is not loose but if I push against it slightly, the light works, when I let go, the light is off. Don't know what caused this??? Once I fix this issue, I'll go back to no light like EOD Guy and a resister in the line only.
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Old 07-10-2013, 09:50 PM
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I don't even use a resistor. I do have a digital volt meter gauge in the cluster, that lets me know when the alt is malfunctioning
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