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Old 10-12-2020, 07:30 PM
Rusty76 Rusty76 is offline
258 I6
Join Date: Jul 15, 2018
Location: Cochrane
Posts: 313
What gives? Alternator Question

So I replaced my alternator with an ACDelco s10 3 wire. Everything has been running perfect for the last 2 months. After a longer burn around the country road I stop for gas. Go to leave and nothing but clicking, clicking, clicking...
Figured it was the battery (which is new) and two footed it over to the parts store to buy one of those jumper packs. Jumped the jeep and headed home.
Turned her off, tried to fire up and again nothing but clicks.

I'm horrible at diagnosing stuff. Brief summary of what I've done.

Took Battery to Napa for test, came back fine after charge and load test.
Installed newly charged batt and test with multimeter above, 12.6v. Fired up
tested batt with lights on and it drops below 12v. I believe it is suppose to be 14 ish with alternator running. When I move my test light around everything lights up. Power at alternator post, power at the diode. So it seems to me like the alternator is not charging the battery.

New guy here.. I did notice that no wires go directly from alternator to battery or starter solenoid. I have rewired using ez kit. 3 wires.
Excite wire goes back into panel, other wire beside excite loops over to main post. Alt power wire comes from panel and goes to main post.

Any other things I can test or look for?

1976 Jeep Wagoneer
Rebuilt, 360, TH400, QT.
Still not running. Soon!
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Old 10-15-2020, 10:01 AM
tgreese's Avatar
tgreese tgreese is offline
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,293
Mmm. When you replace the factory wiring with an aftermarket harness, you take all the understanding and debugging on yourself. Do you have a wiring diagram for the new harness? That the alternator is from an S10 (?) is kind of irrelevant. Or maybe you mean 10SI? That's a type of Delco alternator. These need 3 wires - the exciter from the ignition switch, the large charge wire to the battery, and the voltage sense wire that typically wraps back to the charge wire. If you have this type of alternator, I suggest you learn how these connections work and see how they are wired in your harness diagram.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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Old 10-22-2020, 07:58 PM
Rusty76 Rusty76 is offline
258 I6
Join Date: Jul 15, 2018
Location: Cochrane
Posts: 313
Yes sorry 10SI. Well after spending hours thinking it was my fault and having no luck I decided to buy a new 10SI and guess what it works!
This was my first taste of remanufactured duds.
Thanks for the help.
1976 Jeep Wagoneer
Rebuilt, 360, TH400, QT.
Still not running. Soon!
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Old 10-23-2020, 11:45 AM
rang-a-stang's Avatar
rang-a-stang rang-a-stang is offline
Join Date: Oct 31, 2016
Location: Camarillo, CA
Posts: 3,775
I hear you! I have been amazed at how much crap is sold these days. Nowadays, when I shop for parts, I almost always buy the best warranty. Then when it fails (we all know it will fail soon) at least the part gets replaced without a cost. It sucks when that part is something like a water pump that is going to cost another $30 in fluids/gaskets but at least when it's something like a alt, it only wastes your time.

Glad you are back on the road!
79 Cherokee Chief (passed CA smog check Sept 2020)
(Cherokee Build Thread)
11 Nissan Pathfinder Silver Edition 4x4
09 Mazdaspeed3 Grand Touring
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