PART II: Installing a Denso
So with the chart in hand you're ready to go out and search for an alternator. After adding a GPS to the Jeep, Aux. lights, stereo with amp and subwoofer, winch and the FoMoCo Electric Fan. The stock alternator was left struggling so say the least. The easiest way to tell is if you can hear the high pitch whine of the alternator. Under a heavy load the alternator will whine as it tries to keep up with the power draw.
Is the list your only choice? No, you can get custom wound alternators that are rebuilt by experts who can bump up the amperage. Sometimes you can get your stock alternator reworked depending on the size of the alternator housing.
As you can see with the list. TJ's have a leg up on YJ's. (XJ's would depend on the year. ) A stock YJ will normally have a 75A alternator stock. There is a Heavy Duty package that replaces that with a 90A alternator. The TJ, upped that to an 81A with an option for an 117A. Even if you own a TJ, it would be a good idea to upgrade the alternator. The most common alternator you can fins is probably the 136A version. If you want to go higher you might want to check out a local alternator rebuilder or check ebay. That's were I got mine.
Instead of getting a 136A, I settled on a custom built 170A alternator which came with a two-year warranty. The alternator showed up with a 7-groove pulley. Most likely this was removed from a Dodge truck. There was no other markings on the alternator. The overall size of the new alternator was a little larger then the stock 75A it was replacing. I have read that the 7-groove pulley can be used but it's very easy to swap the pulleys. You will need a gear puller and it's a whole lot easier if you have an impact wrench.
Before I get too far ahead of myself, you will need to get the old alternator out. On a YJ, you will need to loosen three bolts on the Power Steering Pump and loosen the tensioner lock nut. On a TJ, you will need to loosen the tension idler pulley under the Power Steering Pump.
There are two bolts holding the alternator on. The upper bolt passes though two brackets and has a nut on the end. The other bolt passes through the alternator and into the engine bracket. Before you can remove the alternator you will need to disconnect the Oil Pressure sensor which is located on the engine block behind the alternator. It should be a light blue wire. Once that is disconnected the alternator can now be pulled out towards the passenger fender. With the alternator turned around so it faces the firewall, you will see a black box at the top with some bolts. Undo the field terminal connectors, ground, hold down and Positive terminal.
Once those are disconnected the alternator will them come out. With the alternator on the bench you will need to remove the plastic insulator and swap it with the one from the old alternator. There is a alignment pin so the insulator can only be installed one way. The Dodge unit point the wrong way.
Reverse the steps and make sure you connect the Oil Pressure sensor back.
The last step is to start the engine up. Even with the electric fan turning all the time, once the engine starts up, the alternator has no problems keeping up. No more whine!
