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rketr 09-19-2007 12:29 AM

HOWTO: Alternator Upgrade
Did this a while back and forgot I actually did a writeup on it...
enjoy :D

Difficulty rating: 2 out of 5
Estimated time: 30 mins

In an effort to support all the extra stuff I keep adding to my TJ, I decided to upgrade my alternator recently. The stock alternator, from what I can tell (since I cannot find record of this particular model online) is a 117 amp Denso. After checking around a bit for the best bang, I ended up with a Mean Green high performance 200 amp alternator for my ’03 4.0L TJ. 200 amp might be overkill, but hey, that’s the point isn’t it ;) Got it on for $359.99. Was the same price as a 140Amp model so I figured why not shoot for more bang...

In case you have never done an alternator swap, here’s a generic quick howto. Since there are only 4 nuts/bolts involved, it’s an easy task that really doesn’t require much effort.

Now as a caveat, keep in mind that I’m not a mechanic in any sense of the word. I just figure stuff out – computer stuff mostly – for a living and thought I’d help out other geek-chanics out there that might want to try their hand at getting a little dirty. In short, if your stuff blows up or shorts out, don’t come crying to me.

During the installation, I’d recommend that you:
1) replace the fan belt (since it’ll be off anyway). Fan belts can be found at your local auto shop and should run anywhere from $20 to $35 or so.
2) upgrade the wire connecting the alternator to the fuse box. The wire upgrade can be done by picking up 2 or 3 feet of #2 stranded cable from Home Depot or Lowes for around $0.50-$0.60 a foot and a couple of 3/8 #2 crimpable lug ends ($1.50 - $2 for a pair) from your local auto shop. Measure it out so you’ll follow the existing wire and leave a few inches of excess for engine vibration and whatnot – you do not want the wire to be tight when installed. Once you’ve crimped and heat shrinked the new wire (maybe I’ll write a howto on that too), add vs. replace it to the overall setup. By this I mean that once you reattach everything, put the old cable back in place and install the new cable on top of it. The reason for this is primarily so you won’t have to cut the wire and have a loose end on the fuse box side. Trace the existing wire to see what I mean.

During the installation, you’ll need a 1/2 “ socket wrench and a few metric sockets ranging from 12 to 15 MM.

Here’s a pic of the two alternators side by side:

The new unit is not much larger, but supplies 71% more amperage to the setup.

First thing you’ll want to do is disconnect the vehicle’s battery. To do so, remove the black / - / negative / ground lug from the battery. Then remove the red / + / positive / hot wire from the battery. For the geek savvy, Red is always FILO.

Ok, now to the replacement…

1. After the battery is disconnected, disconnect the red wire that goes to the fuse box from the existing alternator.
2. Remove/unclip the control wires (not shown) from the back of the existing alternator.
3. Remove the fan belt. Do so by using a 1/2 “ socket on the Fan Belt Tension Arm and pushing the arm toward the ground. The belt will be loose enough to slip off.
4. Remove the Connection 1 and 2 bolts from the existing alternator.
5. Pull the alternator out and set it aside.

Now, simply reverse the process.
1. Put the new alternator in place.
2. Put the two bolts in place and tighten till snug…you’ll finalize the tightening later.
3. Put the new fan belt in place by pulling the tension arm upwards. The proper bend sequence can be found on a sticker on the radiator just up and right outside the picture above. Here’s a tip: allow the smooth pulley just to the right of the alternator to be the last one that you try and put back in place. The belt won’t be tight, but it’ll be snug enough that you cannot easily get it over the ridges of the alternator’s pulley.
4. Reattach the control wire.
5. Reattach the red wire that goes to the fuse box and add the new wire that you’ve prepped.
6. Reattach the battery cables – Red first and Black last.
7. Finalize tightening the two connection bolts. Do not over tighten to the point that they strip.

After running the rig for 15 – 20 mins, recheck your bolt tensions and tighten as needed.

Now tell your wife to come and see that you did the job and didn’t blow anything up :cool:

AzTJ 09-19-2007 12:36 AM

ah, I thought you were going to be using a 136Amp Dodge Ram alternator... What kind of warranty does the MeanGreen offer?

foxinthemudd 09-19-2007 12:37 AM

wrong person AZ thats what I'm gonna use, he was just adding to the discussion...

rketr 09-19-2007 01:15 AM


Originally Posted by foxinthemudd (Post 138346)
wrong person AZ thats what I'm gonna use, he was just adding to the discussion...


Don't remember what the warranty is...twas over a year ago. Alt may be different, but the howto should still work...

foxinthemudd 09-19-2007 01:18 AM

thanks for the write up RK, I've always wanted one of the mean greens but could never find them for the price that I could do. maybe if I find one at a swap meet or something.

AzTJ 09-19-2007 02:01 AM


Originally Posted by foxinthemudd (Post 138346)
wrong person AZ thats what I'm gonna use, he was just adding to the discussion...

:doh::doh::doh: oops.

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