Alternator upgrade

I have been wanting to upgrade my 90amp alt. when i turn on the heater i notice the volt gauge drop down a fair amout below 14 forget if i turm on the lights turn signals defroster and wipers i have tested the alt it is good maybe my gauge is bad i guess. in any event i want to upgrade the alternator but my local rebuilder says that anything bigger then the 90amp might be too big but yet i see other companies selling huge amp alts. any advice?

Maybe 5-90 could step in on this subject, but I know that upgraded cables and grounds are a good start. I am wondering if there is anything you can do for the alternator charge wire itself. How much amps will the stock one handle and what guage and how should that be upgraded too.

I went the 136A route:

http://www.bc4x4.com/tech/2004/jeepalt/

Very happy with it. The crappy factory gauge was usually well below 14 prior, now it's pretty much at 14 all the time. I haven't upgraded the wiring, but it's definitely a good idea.

What year? It's important...

I'm going to make an assumption that your rig is somewhere between 1993 and 1999 - those were usually equipped with 90A Nippondenso alternators. If you get one from a 2000-2001, you have a good shot at getting a 117A unit. Or, you can get a unit from a V8 ZJ/WJ/WK, Dakota, or Durango, and probably score a 136A alternator.

The 117A has the same size frame as the 90A, and should go in with no trouble. The 136A is somewhat larger, and does require some "clearance grinding" of the mounting area to fit properly - about 3/16"-1/4" off of the mounting area, IIRC. It's been discussed here before. The PCM regulator can handle it with no trouble, but you will want to upgrade your mains and the fuse protection for the alternator output circuit. Look down...:loveu:

If you have a 1990 or earler, you don't have a 90A stocker. However, you do have a Delco - and they're easy for shops to upgrade. I have a 1988 with a Delco CS-130 that started life as an 80A unit - it's now rated for 180A, with a max tested output of ~198A. Schmoov...

And, if you want to get a "new reman" and can't find a shop locally, you can click the link in my sig and call Rod at San Jose Generator - he's the shop I've been using for years, and I talked him into doing mail-order a few years back. So far, everyone here who has ordered from him has been happy with his work.

Hey 5-90...does your "guy" by any chance take reman alternators that are bad, and turn them into 140Amp alternators? I don't know if it's fixable, but I put a bumper bolt dent into my alternator on the side...and it was a reman. I'd like an upgrade in the future, sounds like you have the ticket.

~Scott

Muddy Beast said:

Hey 5-90...does your "guy" by any chance take reman alternators that are bad, and turn them into 140Amp alternators? I don't know if it's fixable, but I put a bumper bolt dent into my alternator on the side...and it was a reman. I'd like an upgrade in the future, sounds like you have the ticket.

~Scott

Click to expand...

I haven't had impetus to ask him, so I honestly don't know. Sounds like something that could be handled with a quick phone call (and it would mean more coming from you guys than from me...)

The main reason I tend to push him out there is simple - the more we can generate from him from the site, the more I can probably talk him into doing. This would give us options beyond spendy outfits like Powermaster, Mean Green, National, and the like. Not that there's anything wrong with their work (per reports from the field,) but they do tend toward being high-dollar goodies, and not everyone needs the capacity they offer. There aren't many "mid-line" options out there, and I'd like to correct that. That's why I'm working with Rod.

His current offerings are listed on the site (under the San Jose Generator pages,) and I check in with him every now and again to try to talk him into offering something else. I need to see about expanding that page anyhow...

So, give him a call, see what he says, and make sure to mention that you saw the site I built for him. The more he hears about that, the more I can talk to him about doing more!

what's his turn around time?

5-90, I was looking at getting the 130 from Rod but figured I should make sure what I have currently was worth replacing as I thought I remembered my alternator being rated higher than 90 amps. It's a '99 Classic 4.0 auto which according to your above post should be a 90. I figured maybe I had a late 99 model that may have possibly gotten the 117 you referred to for the 00-01 year. I just checked my window sticker (yeah I still have it, I'm sick, I know...) and it lists my standard equipment alternator at 124 amps. I looked for a rating plate on the alternator itself but couldn't find one. I know my alternator has never been replaced as I'm the original owner. What's the deal?

shawnxj said:

what's his turn around time?

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Typically, a day or so. Shipping (IIRC) is Fedex Ground, so about three days for that (it's cheaper for him than the Postal People - alternators don't fit in any of the Flat Rate boxes.)

I put in the Dodge Durango one in my 1994 and it is not that hard. Take the bracket off the rig trace for the new alt. Grind for fit then grind two spots on the block and bolt it up.

problem is I dont have a shop or garage to do it in so im gonna have to take it to a mechanic to have it installed then I'm just going to upgrade the wires I dont even know what ones i need to change yet i am just going to look at all the wires that go to the alt and battery and go with larger gauge so this alt that i will be buying I must be able to just hand over to someone and say here ya go install it..

bobhere73 said:

problem is I dont have a shop or garage to do it in so im gonna have to take it to a mechanic to have it installed then I'm just going to upgrade the wires I dont even know what ones i need to change yet i am just going to look at all the wires that go to the alt and battery and go with larger gauge so this alt that i will be buying I must be able to just hand over to someone and say here ya go install it..

Click to expand...

There are a few things to consider (and it's really not that difficult to do, either. An alternator can be changed on the roadside with hand tools; and if you need a shop, garage, or airtools, I'm sure you can post up in your local chapter and find someone willing to help you.)

The "cheap way out" for an upgrade is the ZJ/WJ/Durango/Dakota V8 swap - but that does require a bit of grinding to clear the larger armature frame on the 136A unit. I understand that Mean Green, Powermaster, et al units are a drop-in installation, but they're spendy. And Rod (San Jose Generator - the shop I use) can fix you up with a drop-in 130A unit for a buck an amp. ($125.00 + pack & post, actually - but that's still rather less than the big boys. I have great faith in his work, I've been using it for years.)

As far as wiring upgrades, bear in mind that you will need to replace the alternator lead to take full advantage of the new unit, and you'll need to make sure to upgrade the fuse protection in that circuit (OEMs usually use "just enough wire" for the OEM application. The circuit is then fused accordingly.) If you hit me backchannel, I can get you pointed in a good direction on that - you can click the link in my sig for both San Jose Generator and myself. This will give you an upgrade solution you can handle with basic hand tools (socket wrenches, a drill, and a hex key,) in an hour or so. In the driveway. Sans a shop or anything else complex. I trust you have at least basic hand tools?

Bear in mind that the alternator lead doesn't run directly to the battery - it runs into primary distribution via some variety of fuse device (on RENIX rigs, it went to the screwpost on the starter motor relay by way of a fusible link. Later models got in by way of the PDC, and either a fusible link segment or a pair of MAXI60 fuses in the PDC itself - depending on version.)

Bear one thing in mind about "testing" - if you take your alternator in to have the parts house put on the bench, they're testing voltage output at low current. This is not RPT not and effective test! The little read Bear ARBST tester gives somewhat better results, but I consider even those suspect. I have a 100A load box that I use in conjunction with a DMM for checking - if it's still suspect after that (or if it's not rated for 100A max output,) I'll pull the thing out and take it to an alternator shop to get wrung out on the bench there - chances are, he can do a much better job (I know Rod can. I tend to assume that alternator shops are going to be similar nationwide. Rod's bench looks like something out of a Frankenstein movie, and it can tell you exactly what's wrong with the thing!)

back to the OP, I had the same amperage drop problem with lights and wipers and stuff like that, i got 5-90s main upgrade and i no longer have the voltage drop. its good stuff... I still plan on upgrading the alt just for giggles and more electric goodies i plan on putting in that just bought me some time to save my pennies

Can i just swap an alternator from an 00-01 without changing any wiring?? Ive got a 99 and I guess it has the 90 amp I have a problem with my headlights on and my defrost. WHen the condenser fan kicks on my lights dim until the alt catchs back up. WHat will solve this.

jeepnatv4life said:

Can i just swap an alternator from an 00-01 without changing any wiring?? Ive got a 99 and I guess it has the 90 amp I have a problem with my headlights on and my defrost. WHen the condenser fan kicks on my lights dim until the alt catchs back up. WHat will solve this.

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1) You still have to grind the mounting to clear the frame of the alternator.

2) If you swing to full output, you're likely to blow the fuse/fusible link in the circuit - an alternator doesn't "live" at full output (that's what the regulator controls - I know it's called a "voltage regulator," but it regulates current. Voltage and current are mathematically related.) If you need more current, you have to make sure you can handle it.

Of course, and alternator isn't really able to generate more than a smallish percentage of its maximum output (35-40%, typically) until it reaches a spindle speed of ~3,000rpm. Given the ratio between the crankshaft pully and the alternator pully, this means a crankshaft speed of 1,200rpm or so. Try this - turn on what you note is going goofy, and idle. Then, bump up your idle to 1,200-1,300rpm, and see if the lights get brighter and the voltmeter tips up - I'm betting it will.

This doesn't indicate that there is anything wrong with your alternator - just that you're overloading it at idle speed. Once you pick up the spindle speed of the thing, it can catch up (and you're not "running on the battery" to make up the shortfall.) An upgrade will probably help you, but it's a way to make sure there isn't actually something wrong with the alternator to begin with...

5-90, What is the diameter of the vibration damper?

To get the optimum spindle speed it should be;

Damper diameter X alternator pulley diameter X engine RPM's = ??

Is it a 3:1 ratio?

techno1154 said:

5-90, What is the diameter of the vibration damper?

To get the optimum spindle speed it should be;

Damper diameter X alternator pulley diameter X engine RPM's = ??

Is it a 3:1 ratio?

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I have not measured them with any sort of exactness - it's just an eyeball guess. I know Rod spins them ~3,000rpm for a full-current test, and going off of the estimated 3:1 ratio, and allowing some room for error, I've found that 1,200rpm or so seems to turn the trick for our rigs. It's also a fairly standard "on-vehicle test rpm" when you haven't taken the thing out yet.

Your logic is correct, I just haven't had a chance to measure. However, your maths need a slight correction: [(damper dia)/(pully dia)] x damper speed = spindle speed. MA of a pully system is calculated by the ratio of (drive dia)/(driven dia) (similar to gearsets - but you use tooth counts for gearsets, and not actual diameter. Gears don't slip, while pully/belt systems can and usually do. That's why you tend to allow that little bit extra. If you were to compare input/output for a smooth belt vice a cogged belt at significant speeds or torques, you'd see what I'm talking about...)

Thanks for the correction. I jotted every thing down without thinking.

The 3:1 ratio is just a guess based on the RPM's you suggested verses the alternator pulley size of about 2.25". I am in the caribbean, my XJ is in Miami.

techno1154 said:

Thanks for the correction. I jotted every thing down without thinking.

The 3:1 ratio is just a guess based on the RPM's you suggested verses the alternator pulley size of about 2.25". I am in the caribbean, my XJ is in Miami.

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3:1 is pretty much what I estimate, then I added a "slip factor" for things being loaded (the "slip factor" increases as load on the drive belt increases. As alternator output increases, its load on the drive belt increases. You get the idea.)

One of these days, I'm going to have to measure the old HD ring I've got out on my workbench. It's been out there for a while now, I've just been out of roundtuits - when I get more in, other things demand my time (at least I haven't had any medical emergencies in a while...)