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Unread 05-20-2010, 08:53 PM   #1
rocknjeep
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Alternator upgrade questions.

So my alternator is pretty much ready to die. I want to upgrade to the 136amp one out of a 98 Grand Cherokee. I currently have the original alternator from 87. What do I need to do to make it work? Or can I? I know it's a bolt in situation and that it will fit. But I'm assuming I'd need to mess with some wiring to make it work. Have any of you guys done this before?

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Unread 05-20-2010, 09:05 PM   #2
rocknjeep
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and i do believe from more reading it's the delco. why the PO who put in a 4.0L out of a cherokee didn't keep it MPI or use the alternator that had I'll never know.
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Unread 05-20-2010, 09:08 PM   #3
rocknjeep
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and now with further research I think I may have solved the problem I was looking at.

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Unread 05-20-2010, 09:12 PM   #4
rocknjeep
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now my question is am I going to blow up the jeep by going from 78amps to 136amps?
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Unread 05-20-2010, 09:26 PM   #5
dodger889
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Just use a heavier led wire for the battery to the alt. +
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Unread 05-20-2010, 09:39 PM   #6
5-90
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Quote:
Originally Posted by rocknjeep View Post
So my alternator is pretty much ready to die. I want to upgrade to the 136amp one out of a 98 Grand Cherokee. I currently have the original alternator from 87. What do I need to do to make it work? Or can I? I know it's a bolt in situation and that it will fit. But I'm assuming I'd need to mess with some wiring to make it work. Have any of you guys done this before?
I seem to explain this about once a week, somewhere.

Check your alternator - if it's OEM, the 136A ZJ/WJ upgrade will not just bolt in and work!

Prior to 1991, Jeeps were still built to AMC specs. That means Delco internally-regulated alternators (the XJ and MJ got the CS-130, and the YJ got the 12SI.)

The Nippondenso, used by Chrysler 1991-up, is externally regulated by a circuit in the PCM. Therefore, you will not have a voltage regulator, and one of two things will happen (depending on how you end up wiring the thing up):

1) You don't connect anything at all to the two studs on the back, and you get no output (due to no input to the field coils.)

2) You do some cutting and crimping, and feed the regulator sense circuit to the field coils. The field coils typically get 0.5-4.0VDC (more voltage to the field coils means more current out of the alternator,) but the regulator sense circuit means full system voltage. This means that:
A) The alternator will swing well beyond max output - we're talking 90-100VAC @ 300-400A.
B) The diodes will either blow out ("open") or short through ("closed" or "short".) If they "fail open," you won't get anything out of the alternator. If they "fail short" or "fail closed," you'll get that 90-100VAC @ 300-400A, and that will blow out pretty much all of your solid-state electronics!

There's an alternator ID guide on my site for later models (Kelley's Works in Progress & San Jose Generator, at the moment. I'll be reorganising the site sometime soon...) to help you figure out which you have. The first pair of pix is front/back on the 12SI, the second pair is F/B on the CS-130, and the third set is F/B on the ND.

This doesn't mean you're boned - the Delco SI and CS series alternators are actually the most popular alternators for conversion installs, kit builds, secondary installs, marine installs, industrial equipment, and quite a few other things (I once overhauled a Hobart GPU - Ground Power Unit - that used a Ford 140ci long block, Ford 122ci bolt-ons, and a Delco 12SI wound to 40A to keep the engine running. Most bizarre damned thing I'd worked on in years...)

Any competent shop can upwind a Delco for you in short order, and getting a Delco wound for 140-150A is a piece of caek.

NB: If you uprate your alternator, you will need to upgrade your cabling and fuse protection! I can help you with that, if you need it.
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Unread 05-20-2010, 10:40 PM   #7
jbolty
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what he said ^^^^.

you want a CS-144, unless you are now running a 4.0 and related electronics
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Unread 05-21-2010, 05:49 AM   #8
Que89YJ
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If the PO did not install the computer when he converted over to the 4.0L then you need to use the CS-144. The Voltage Regulator for the post 1990 are in the ECU. No ECU means no regulator. The 1990 and prior are internally regulated. The CS 144 is the right one for you
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