Higher than Stock Alt

I am looking into an alternator that is better output than stock. I want something that will last. Also help in removing my old one, you know tips or tricks would help here to. My 90amp stocker is putting out 30amps . Suggestions and help here is appreciated.

Jeff

how are you measuring the current from the alternator? if you are measuring the inline current while at idle, (800-1000rpm) will will be getting at most about half the rated output. if you rev the engine to around 1400rpm, you will see closer to the 90 amps.

also, the alternator will not generate more current than is required by the vehicle. if your jeep only requires 30amps to run the engine and accessories, than only 30 amps will be generated.

ihscoutlover said:

I am looking into an alternator that is better output than stock. I want something that will last. Also help in removing my old one, you know tips or tricks would help here to. My 90amp stocker is putting out 30amps . Suggestions and help here is appreciated.

Jeff

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1) What year? (here we go again...) The alternator did change considerably over the years...

2) h2opete is correct about alternator output - testing at idle is no gage. Alternator output is typically tested at about 1200rpm at the crankshaft, or about 3000-3500rpm at the spindle. Also, he's correct about the regulator - if the system doesn't seem to need but about 30A, it's only going to get about 30A. You have to load it to test it.

3) What sort of power levels are you looking for, and how much are you willing to spend?

I have to run an MX7000 Lightbar, the rear defrost, the heater, and the headlights, at the same time. Without running the lightbar, all the others tax the system to the point where at a stoplight, it almost wants to stall. I do a neutral drop, add some gas, and it is fine, and it kinda hesitates for a moment, then I watch my plug in cigarette lighter meter go from about 10volts to 13.4, which is where it normally runs. Thoughts as to testing it?

Jeff

ihscoutlover said:

I have to run an MX7000 Lightbar, the rear defrost, the heater, and the headlights, at the same time. Without running the lightbar, all the others tax the system to the point where at a stoplight, it almost wants to stall. I do a neutral drop, add some gas, and it is fine, and it kinda hesitates for a moment, then I watch my plug in cigarette lighter meter go from about 10volts to 13.4, which is where it normally runs. Thoughts as to testing it?

Jeff

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That's why the later (Police/Fleet) have the "Extended Idle" switch, to bring the kerb idle up to around 1100rpm or so. That allows all the lights to run without lugging the engine.

Again - what year? The OBD-II XJ (1997-up) has provision for the switch, so it can be added. OBD-I and RENIX (1991-1995 and 1987-1990) will need a bit more work - it's probably easier to add a hand throttle with a friction lock.

There's a reason I ask the questions I ask - I actually do need to know to help you better...

But the most current I was getting after running it up to a higher idle was only the 30 amps. This is why I was trying to figure out either how to test it on the vehicle, or how to load it to make sure it is putting out the correct amperage. I am in the process of installing the Extended Idle switch, I just haven't figgered out how I am going to route the wires. My fuse block has the power wire missing, and I have the complete wiring for the Idle Switch, including the factory connectors. I am in the process of adding some pics to the writeup, but I cannot seem to find out why I cannot post pics. I PM'd a moderator, so hopefully this will yield some help. Once I get the ability to do the conversion, I will do a complete tech writeup for those that want to do the same. I will also find out what factory part numbers are needed to do the install, should others want the factory switch look, but run the wiring themselves. This way all can benefit from my work, which could yield better results overall. In the meantime, I will post on the alternator testing and see what I can come up with. Thanks

Jeff

One more time - what year? It really does matter, and that's why I keep asking...

My bad, its a 1994 4.0L, AW4. If you need some other specs let me know. Do you know if the Police packages actually had a "larger" amperage alternator? Sorry for the confusion.

Jeff

ihscoutlover said:

My bad, its a 1994 4.0L, AW4. If you need some other specs let me know. Do you know if the Police packages actually had a "larger" amperage alternator? Sorry for the confusion.

Jeff

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Now we're getting somewhere! I think the OEM for that year was a 90A Nippondenso, but it can be readily upgrade to a 136A ND from a later ZJ/WJ or Durango (I think you'll need to grind a bit.) Also, you're likely to need to use a hand throttle - get a control cable with a friction lock (industrial supply house, or aviation house for kitbuilders. They're used on homebuilt aircraft and a good deal of industrial stationary equipment) to control your throttle separately from the accelerator pedal. You don't have the circuit built into your PCM for the "Extended Idle" switch (that was just the OBD-II PCMs.)

If you're going to be sitting still with all that lighting going on, you're going to need to idle around 1100-1200rpm on demand (not all the time, tho.) Even the higher-output alternator probably won't be able to keep up - assuming you get 40% of full output at idle, you're looking at going to 54.4A (from 36.0,) and you'll need 25-30A to keep the engine idling and the electronics going.

You can check outfits like Powermaster or Mean Green - going to up around 200A will net you ~80A at idle, but you're going to spend some cash to make that happen (I think the Mean Greens run around $200 - and the Powermasters are comparable.) They may also have them wound to give you a higher percentage of full output at idle - so you may see around 110-120A, vice 80 (or 35-55.)

The Police rigs may have had the 136A alternator (lemme check... 1991-1996 had 90A, 1997-1998 had 90A with a 120A HD option, and 1999-2001 had 117A.) So no, they just had a 120A. Likely that's still plenty - once you kick on the extended idle switch. Even your 90A will probably serve, once you get the spindle speed up.

Look into the hand throttle first - not only is it a cheaper mod, but you're going to want the thing anyhow (even with the higher alternator.)

There is a 150amp version of the nippondenso that came stock on the 1998 5.9 ZJ.

Slo-Sho said:

There is a 150amp version of the nippondenso that came stock on the 1998 5.9 ZJ.

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Close. 160A, on the 2005WJ w/4.7L V8 (per my catalogue, anyhow. That's the section I'm working on - alternators and starters.) I haven't had the chance to compare mountings yet, tho. I'd think it would work, but I can't give you anything more positive than that...

You could check out my thread on the Extended Idle Switch install. I got one off a parted out Police XJ that was rolled. I got all the factory connections, and the full run of wire. This way I can de-install it for another XJ later. In the meantime, if the stock one is adequate, I can live with that. Is there an accurate way of checking the output to verify its total amperage? I had it tested and during the test it was run up over about 1200rpm, but it wasn't "loaded", in other words, I didn't turn on lights, accessories and such to see if it kicked up the output, which is regualted by the ECM if I am correct? I guess I will go with putting on a new belt, and tightening the hell out of it. Mine isn't real loose, but I don't want to take any chances. I also don't know when mine was ever replaced, and the XJ has 227k on it now. Should I go ahead and replace it anyways? I just don't want to take it out, take it to the parts store, test it, it shows good and then I have to go and re-install it again. I want to do this once and once only, and I didn't know if there is an easier way to do that. Oh, and sorry about the year 5-90, I didn't think that mattered a whole lot. I knew there were differences, but I didn't respond to that one correctly. My bad. Thanks and keep the suggestions coming. By the way, most parts stores want $120+ for a rebuilt one, and I figgered the Mean Green units were maybe better than a parts store rebuild. Thoughts here? Also, all the XJ's had the built in part for the Extended Idle, there is just no actual circuit in the fusebox, and the firewall grommet for the wires, but the actual wires are still there in the ECM harness, which is where the actual connection is going to be made. I will show you once I have the install completed.

Jeff

ihscoutlover said:

You could check out my thread on the Extended Idle Switch install. I got one off a parted out Police XJ that was rolled. I got all the factory connections, and the full run of wire. This way I can de-install it for another XJ later. In the meantime, if the stock one is adequate, I can live with that. Is there an accurate way of checking the output to verify its total amperage? I had it tested and during the test it was run up over about 1200rpm, but it wasn't "loaded", in other words, I didn't turn on lights, accessories and such to see if it kicked up the output, which is regualted by the ECM if I am correct? I guess I will go with putting on a new belt, and tightening the hell out of it. Mine isn't real loose, but I don't want to take any chances. I also don't know when mine was ever replaced, and the XJ has 227k on it now. Should I go ahead and replace it anyways? I just don't want to take it out, take it to the parts store, test it, it shows good and then I have to go and re-install it again. I want to do this once and once only, and I didn't know if there is an easier way to do that. Oh, and sorry about the year 5-90, I didn't think that mattered a whole lot. I knew there were differences, but I didn't respond to that one correctly. My bad. Thanks and keep the suggestions coming. By the way, most parts stores want $120+ for a rebuilt one, and I figgered the Mean Green units were maybe better than a parts store rebuild. Thoughts here? Also, all the XJ's had the built in part for the Extended Idle, there is just no actual circuit in the fusebox, and the firewall grommet for the wires, but the actual wires are still there in the ECM harness, which is where the actual connection is going to be made. I will show you once I have the install completed.

Jeff

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Half marks - all of the OBD-II XJs have provision for the "Extended Idle" switch. It's not present in OBD-I, and there was a thread going on trying to figure out an easy way to do it (with OBD-II - 1996-2001 - it's a simple matter of purchasing and installing the switch.)

Well the XJ my Extended Idle Switch assembly came off of was a '95, and it matched mine except that mine had cruise, and it had a 242 transfer case. I will let you know, as I have FSM for my '94, and it doesn't refer much to this, but it does tell about checking and function of the circuit. I will post up once I locate the pages, and the manual.

56041394aa This is the 150amp big boy.

slo sho, what is it out of? And does it need any modifications to work with a stock '94 XJ, 4.0L, AW4, 231 setup? Is this the one I need to look for when junkyard "shopping"?

Does anyone have a wiring diagram for the ext idel. I want to add it but do not want to pay for the factory switch assembly.

jforse said:

Does anyone have a wiring diagram for the ext idel. I want to add it but do not want to pay for the factory switch assembly.

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I don't have it handy but, if you search........ There are several threads that cover this.

Haleyes said:

I don't have it handy but, if you search........ There are several threads that cover this.

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Did search. Went through 7 pages and didnt find a wiring diagram for a OBD2 XJ. There is one for the OBD1. Couldnt find the OBD2.

Jforse, to my understanding all the OBDII units already were "prewired" for this option. You would need a switch, and they are not that expensive. Check out this site: www.jeepsareus.com he should be able to fix you up for the switch I believe that is also his ebay name. If you use that switch, you will be able to retain the factory look. HTH, and I wish yours was a OBD I, as that wiring diagram is what I am working on for mine right now. Take a moment and look at my posting, you might get some ideas.

Jeff