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Discussion Starter · #1 ·
In the case that anyone is curious, there IS an inexpensive & fairly easy alternator swap for 93 - 99 Wrangler YJ's & TJ's. The stock alternator on these years of Wranglers only puts out 90 Amps max. If you add electric cooling fans, extra off road lighting, a winch, etc; that poor little 90 amp alternator will have problems keeping up if it even does.

Of coarse there are the high dollar Mean Green, Power Master, etc. alternators, but the truth of the matter is you are looking at a very costly upgrade going that route. Also, the ECU on these Jeeps don't always take kindly to aftermarket alternators. The alternator on these year models of Jeeps is externally regulated by your ECU; this means that if you aren't running a stock OEM Jeep alternator, issues may arise with the ECU causing your service engine light to come on & for it to start throwing various codes because it does not sense that the alternator is there or if it is charging.

However, there IS an alternator upgrade you can do.
 

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Discussion Starter · #2 ·
Here is the good news:

The alternator that comes stock in the '98 - '99 Jeep Grand Cherokee's (WJ) with the V-8 engine produces 135 amps peak. That's 45 amps over the stock 90 amp alternator that comes stock in the Wrangler - a 50% increase in charging capability from a stock OEM alternator. The alternator from a '98 - '99 WJ as mentioned will bolt right into a '93 - '95 YJ with very few modification, on some TJ's you may have to grind the alternator side of the existing alternator brackets already on your engine down a little ( around 1/4" or less) so the bolt holes will line up.
(NOTE: Make sure you look for the V-8 version only, the case on the 6 cylinder version has a different design & will not bolt up)

Just for the record; I'm sure there are other year models & Jeep vehicles that have alternators that will work, but the swap mentioned above is from the Jeep vehicles that I know for a fact will work without any issues.
 

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Discussion Starter · #3 ·
Write Up:

For my '94 YJ, I went to the wrecking yard & found a fairly new 135 amp alternator off of a '98 Grand Cherokee WJ for $30.

As far as doing the swap:

The first thing I did was disconnect both my positive & negative battery cables from the battery
Next, I removed the belt, for YJ's this is done by loosening the 4 - 13mm bolts on the power steering pump bracket, then turning the tensioner bolt counter clockwise until the belt is loose enough to slip off.

Once the belt was off, I disconnected the 8 awg main power lead from the charging post with a 10mm deep socket, then removed the nuts on either side of the exciter wire module that holds both ground terminals to the back of the alternator with a 10mm deep socket as well. The one closest to the engine block can be tricky to get to since you can't see it, but I will post a picture so you can see what I'm talking about. Once the nuts were removed from the ground terminals, I removed the two smaller nuts holding the exciter wire module to the alternator with a 7mm deep socket. After removing all wires & terminals from the alternator, I removed the top & bottom bolts holding the alternator to the bracket with a 15mm socket, extension, & a 15mm backup for the nut on the backside of the top bolt.

Note: If you have an A/C compressor & related plumbing, I recommend lowering your old alternator down through the bottom to remove it, that is what I did. This kept me from having to remove A/C compressor as well to get it out & to put the new one in.



Here is the old 90 amp alternator (Top) sitting next to the 135 amp alternator from the '98 WJ. Quite a noticable size difference.



Here is the backside of both alternators so you can see how the wiring & terminals connect. You can also see that the wires & cables connect exactly the same way, in the same direction, using the existing wires & terminals.



The only thing that is different between the two as far as wire routing, is the direction that the insulator points on the bigger alternator. It is held onto both alternators with a 12mm nut, I gently removed that nut on both alternators & simply put the insulator from the Wrangler alternator onto the larger alternator, it slides right on, then I put the 12mm nut back on & gently snugged it back down.



Wrangler insulator installed



After that, I removed the old harness that came with the bigger alternator from the wrecking yard.

There IS a difference in the pulleys though, the pulley on the Wrangler is designed for a 6 rib belt, & the pulley that comes on the larger alternator is designed for a 7 rib belt. To remedy this, I simply switched the pulleys, the one from the old alternator will slide & bolt right on to the larger alternator. The nut holding both pulleys on takes a 7/8" socket. I used recommend using an impact to remove both pulleys. Once they are removed, I applied a small amount of antiseize to the shaft on the larger alternator then snugged the nut back onto it gently with a few hits from the impact. DO NOT Over Tighten the nut if doing this yourself.



Once I was finished with that, I gave all of the terminals & posts a light coating of lithium grease to help prevent corrosion



Next, it is a GOOD IDEA to drive the bushing for the upper bracket back towards the rear of the alternator to where it matches the position of the bushing that is on the alternator that came out of your Wrangler. I just used a small brass punch & 3 lb shop hammer



At this point, the larger alternator should be ready to be bolted into the Jeep, since I was doing this by myself, I tied a rope to the alternator so I could pull it up from the bottom.



FAIR WARNING: The larger alternator does NOT just pull right into place, it takes quite a bit of wiggling & repositioning to get it up into place.
Once the alternator was in place, I bolted it back up, then connected all of the wires, cables, terminals in the reverse order I took them off in. After that, I put the belt back on, then snugged it back up & retightened the 4 13mm bolts that holds the power steering pump in place.

Pics of the 135 amp alternator once it was installed:







 

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Discussion Starter · #4 ·
WRITE UP Continued:

One thing I did that you may not be able to see in the pics, is I reconnected the 8 awg lead to the main post on the alternator like it was originally, (the post that the large black insulator is fastened to) then I also added & ran a 2 awg cable from the same post directly to the top post of the battery to ensure ALL of the current is getting to the battery along with the rest of the electrical system.

2 awg automotive/welding cable is rated at 190 to 250 amps at 5 foot or less in length. (depending on chart/application)

4 awg automotive/welding cable is rated at 150 amps to 190 ampsat 5 ft. in length or less. (depending on chart/application)

This being said; lengths less than 5 ft. are typically what are used in Jeeps, & most other light duty vehicles for that matter.

The 8 awg cable that is run alone originally on these Jeeps is only rated 60 to 90 amps max (depending on chart/application)

Also, FYI, the 8 awg cable that runs from the alternator runs through your main wiring harness, connects to the fuse box, then the current produced by the alternator runs through your fuse box before it gets to the battery. Adding a larger cable that runs from the main positive post on the alternator to the positive post on your battery will help take a lot of strain off of your Jeep's electrical system.

VERY IMPORTANT MORAL OF THIS EXPLANATION:

If you upgrade your alternator because you are running A LOT of extra accessories; you need to add a 4 awg, 2 awg, or larger cable (depending on load) that runs directly from the main post on the alternator to the top post of the battery as well to prevent electrical shorts &/or fires caused by heat produced from drawing more current through the stock cable than it is rated for.

Here is an example of the battery area where there are a lot of accessories including a large winch & an electric cooling fan which are used on a regular basis. I use military standard battery terminals for the top posts where the 2 awg cables are connected.

Please excuse the mess, not finished with all of the wiring when this pic was taken, still needed to remove butt connectors & solder/heat shrink a few connections, then get it ready for a dual battery rig up. Will post pics when that is finished.

 

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Discussion Starter · #6 ·
Good write up. This same alternator is also on 4.7 dakotas. If you ever need to find s part at the junk yard you can go to Oreillys Web site, look up your part and click the compatability tab. It will give you a list of rigs that shared the same part number. Here's a link to this particular alternator.

http://www.oreillyauto.com/site/c/detail/ULT0/050309/01468.oap?year=1999&make=Jeep&model=Grand%2BCherokee&vi=1431780&ck=Search_01468_1431780_-1&pt=01468&ppt=C0330
Thanks! Now THAT is handy, I appreciate you sharing that. It will definitely help in the future
 

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Man what did I start.
 

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Discussion Starter · #8 ·

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I sent you that right up and you take off and refine it so anyone can do it. That took some work.
 

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Discussion Starter · #10 ·
I sent you that right up and you take off and refine it so anyone can do it. That took some work.
lol, well I really appreciate it. It wasn't that hard at all, you should take some credit for this as well ;)
 

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lol, well I really appreciate it. It wasn't that hard at all, you should take some credit for this as well ;)
I don't think so. You did all the work.
 

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Discussion Starter · #12 ·

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Thanks for the great idea. I highly recommend this upgrade to anyone replacing their stock alternator. My oem alternator was only 75amps. This was very easy to do using the provided instructions as a guide. I used the duralast gold 136 amp alternator, for a 98 Grand Cherokee 5.9 v8, from autozone and upgraded to an optima 870 cranking amp yellow top. Much more cost effective than 200 amp alternatives and made a night and day difference.
 

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This thread was a couple months ago but I'm Curious to know about my 92 YJ as well.
Yup, I did the swap and it's a direct bolt on. Mind you, I used the Cherokee V8 one and EVERYTHING bolted up directly. I did try the durango and dodge ones but they were different on the connections and I didn't want to fluff around with them so I ended up with the Cherokee alternator; however, the alternator itself was shot and not producing enough amps so I ended up just buying a brand new alternator (136 amps for a cherokee) from my local parts store and it was a direct bolt in. I also added the extra power wire as well as the grounds to the alternator bracket, battery to chassis and block to chassis.

Seems to be working well at the moment (knock on wood!!).
 

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I think I received the wrong alternator from eBay it said it fit a 98 jeep grand Cherokee 5.2l and its a 136 amp but the back of this one is different and has a plug. I can order the plug but I have no idea how to wire it to my 94 2.5 YJ. Has anyone done this or know of how to wire it? It looks like the alternator is from a 2002 dodge Dakota.



Here's a wiring diagram for the Dakota


Here's the wiring diagram for the YJ
 
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