Alternator (cs130) wiring and the “exciter.”

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SkylinePCG
Posts: 72
Joined: Tue Apr 16, 2013 11:28 am

Alternator (cs130) wiring and the “exciter.”

Post by SkylinePCG »

-Cs130 in place of the stock 10si
-stock bracket and wiring were intact
-new alternator adapted with Napa/Echlin pigtail ec82

Things were working fine. Battery routinely held 12v and showed 14v when running. Then I tried the bulltear bracket but it didn’t fit with my specific alternators case... another story for another day...

Anyway, I go to reconnect all the wiring that had worked fine before and find the exciter wire had been pulled from its harness, and won’t go back in.

Image

So I go find a new stock replacement for that side of the harness, thinking I’ll solder the wires and be done with it.

Image

But the white wire on the new one is copper strands, unlike the exciter is later discover. I still (mistakenly) attempted to connect the two, and then plugged them into the ec82 si/cs pigtail, which plugs into the alternator
This pigtail appears to have a resister heat shrunk into its yellow wire, out of the box.

Image

So let me just say now, this DOES NOT WORK :)

The battery was dead at the onset I guess, so I jump-boxed the battery. Even with the Key off, as soon as the negative was connected, the starter kicked on, and stayed on AFTER the motor fired up.

I immediately pulled the jump box’s negative, and the starter stopped spinning.

I then cut out the copper/exciter “solder” joint, wondering if it had ever been in use in the first place, and jumped the vehicle again, starting it normally this time.

What wasn’t normal was the 10v showing on the multimeter with the engine running. This lasted 30 seconds until the motor stalled, and coming on here was my next move.

So my question is... what on earth did I do??

And more importantly, how do I get back to running reliably down the road again?

Thomas792
Posts: 54
Joined: Fri Oct 05, 2012 6:02 am

Re: Alternator (cs130) wiring and the “exciter.”

Post by Thomas792 »

I have an 88 GW that I did the conversion to about 9 years ago. It went on very easily but I could not get it to charge. Turns out I had to put a small resistor in one of the lines (power?).

I don't really know what you did. Is it possible that the wires were reversed. I really cannot disconnect mine to trace what I have because I did that once 6 years ago and it took me all day to get it working again. Besides that, mine is not in a running state now.

Looking at my wires coming off the alternator:
I have a thick one connected to a fusible link that is then connected to the heavy duty relay on the passenger front inner fender.
The other is a very thin black wire that disappears under the motor. It looks like it goes to the oil pressure sending unit but that cannot be right. Maybe goes to the starter solenoid?

It's raining here now so I couldn't stay out too long. Hope that helps somewhat or maybe someone else will chime in.
1974 J10 - 401, TH400, QT, D44, 28" tires - Sold under duress
1988 GW - "Mrs Tickety" - 360, 727, NP228, D44, 32" tires
Retired Marine
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Alternator (cs130) wiring and the “exciter.”

Post by tgreese »

In a nutshell -
Your alternator has four connections.

1) Battery - this is the big wire that goes to charge the battery.
2) Ground - typically the alternator grounds through the case, but you may have a separate ground wire.
3) Excite - this provides a boost at startup. The alternator needs some field current to make electricity. Labeled "1" on the alternator, it's one of the small wires on the plug. This is connected to the ignition so that the alternator has some power to "bootstrap" when the key is on.
4) Sense - this connection is used by the internal voltage regulator to adjust the output voltage in response to demand. Labeled "2" on the alternator. On a Jeep with a 10SI, this wire is quite short since it loops back almost immediately to the battery wire.

Connecting the ignition to the excite terminal creates a problem. While the alternator bootstraps, the excite wire is a sink for current. Once the alternator can provide its own field current (self-generation), the excite wire becomes a source of current. So if you simply connect with a wire, you can turn the ignition off and the engine won't stop, sourcing the current it needs directly from the excite wire.

To solve this, the excite wire has an extra component between the ignition and the alternator. This can be
1) A diode - this is a semiconductor that blocks current in one direction. The diode blocks the excite wire from being a source.
2) a resistance wire - bootstrapping only needs a trickle of current, much less than needed by the ignition. The resistance wire limits the amount of current so that the excite wire no longer can power the ignition.
3) a light bulb - the filament of a light bulb works just like a resistance wire. It has the added advantage of working as an amp light. Once the excite wire turns from a sink to a source, the bulb goes out, indicating normal operation. The main problem with a bulb is durability. If the bulb burns out, the alternator may not bootstrap.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Thomas792
Posts: 54
Joined: Fri Oct 05, 2012 6:02 am

Re: Alternator (cs130) wiring and the “exciter.”

Post by Thomas792 »

Look at this thread in the mothership.

http://www.ifsja.org/forums/vb/showthre ... 4+resistor
1974 J10 - 401, TH400, QT, D44, 28" tires - Sold under duress
1988 GW - "Mrs Tickety" - 360, 727, NP228, D44, 32" tires
Retired Marine
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