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Alternator Woes

H

HQuakers

NAXJA Forum User
Location
South Jersey
Back story: Broke a piston skirt in my '97 and had a shop swap in a motor from a '96.

Just got it back and noticed a crazy amount of rattling when driving. Took a look under the Jeep and noticed the alternator is not bolted in all the way(?) and sitting right on the framerail. I was told it was this way on the old motor as well (though not hitting the frame). Appears it may be a larger alternator than stock, but I'm not sure.

I've done some research and haven't found any pictures of a similar problem when using a larger alternator in a stock mount. Anyone familiar this problem and seen similar issues as mine:

87yLx.jpg
 
Lol, i wouldnt be going to that shop again, bastards didnt even tell you your alternator was hanging half loose.
 
Better get that fixed, going to be hell on the alternator bearings. If you are lucky you will have the larger top mount, you will have nearly ½ inch wall thickness, if so you can drill it out and it will drop in w/o grinding.

Keep in mind the alternator to battery cable is designed for a 90 amp alternator and you have the 120 or 136 amp in it now, although I would doubt it can hit that, but if you replace it with another of the same amperage you need to upgrade the charge cable.

An adaptor bracket is not going to work, if you install it in the position it is in you are going to smack the alternator on the frame when the engine torques.

I know it is all about cheap but the stock 90 amp can be built to 150 amps and it bolts right in, we have built them as high as 180 amps. But that is more expensive than a junk yard alternator so I am sure people will keep doing it this way.
 
Better get that fixed, going to be hell on the alternator bearings. If you are lucky you will have the larger top mount, you will have nearly ½ inch wall thickness, if so you can drill it out and it will drop in w/o grinding.

Keep in mind the alternator to battery cable is designed for a 90 amp alternator and you have the 120 or 136 amp in it now, although I would doubt it can hit that, but if you replace it with another of the same amperage you need to upgrade the charge cable.

An adaptor bracket is not going to work, if you install it in the position it is in you are going to smack the alternator on the frame when the engine torques.

I know it is all about cheap but the stock 90 amp can be built to 150 amps and it bolts right in, we have built them as high as 180 amps. But that is more expensive than a junk yard alternator so I am sure people will keep doing it this way.
 
Last edited:
sjkimmel99 said:
I had to grind the mounting bracket to enlarge space where the alternator goes to get it to fit. Don't think the larger alternators will bolt up to the stock bracket without that. I suppose you could make a short strap with two holes in it to bridge the gap between the holes. If the top bolt is in that should control the twisting.
Click to expand...

Ok, I'll pass this info along. Thanks.

90xjblue said:
Lol, i wouldnt be going to that shop again, bastards didnt even tell you your alternator was hanging half loose.
Click to expand...

You have no idea. This is just the tip of the iceberg with this whole situation.

Rush Power Systems said:
Better get that fixed, going to be hell on the alternator bearings. If you are lucky you will have the larger top mount, you will have nearly ½ inch wall thickness, if so you can drill it out and it will drop in w/o grinding.

Keep in mind the alternator to battery cable is designed for a 90 amp alternator and you have the 120 or 136 amp in it now, although I would doubt it can hit that, but if you replace it with another of the same amperage you need to upgrade the charge cable.

An adaptor bracket is not going to work, if you install it in the position it is in you are going to smack the alternator on the frame when the engine torques.

I know it is all about cheap but the stock 90 amp can be built to 150 amps and it bolts right in, we have built them as high as 180 amps. But that is more expensive than a junk yard alternator so I am sure people will keep doing it this way.
Click to expand...

Thank you for the info. This alternator is whatever came in the Jeep when I bought it, so I had no idea it wasn't the factory unit. Heck, I was thinking about upgrading to a larger unit at some point, so I was clueless.

You're right, as it sits now, it hits the frame while driving and it's loud ("can't have a conversation inside" loud).

I do have a stock spare 90A alternator that I can put in there if we can't remedy this problem.

Side question: Are there any ways I can identify this alternator? Markings, serial #s?
 
No problem yes put the 90 amp in before you crack the case on the one you have. If you do you may lock up the alternator and shred your belt. That is if you can’t drill it and don’t want to grind the mounting bracket. I don’t recall the cut off year but on some you actually need to grind on the motor I believe it is in OBD1 era so you are probably OK.
Denso units can be hard to ID, you will have a sticker on the stator stack, but they usually come off, the best way to ID is to take it apart and measure the stator and rotor, however if you can clean it off and get some numbers on the sticker I can look it up for you, don’t use carb cleaner or you will take the numbers off the sticker.
 
Rush Power Systems said:
No problem yes put the 90 amp in before you crack the case on the one you have. If you do you may lock up the alternator and shred your belt. That is if you can’t drill it and don’t want to grind the mounting bracket. I don’t recall the cut off year but on some you actually need to grind on the motor I believe it is in OBD1 era so you are probably OK.
Denso units can be hard to ID, you will have a sticker on the stator stack, but they usually come off, the best way to ID is to take it apart and measure the stator and rotor, however if you can clean it off and get some numbers on the sticker I can look it up for you, don’t use carb cleaner or you will take the numbers off the sticker.
Click to expand...

Alrighty, gonna throw the smaller one on for now until I figure this all out. I'd like to grind the bracket and all to make it fit, but I doubt this shop will want to do that. Frankly, I don't trust them to do it right. I will ID this when I pull it out. Thanks for the info on the sticker.
 
Rush Power Systems said:
drilling out the top mount is easier but grinding the bracket is not that difficult, it is aluminum. the question is do you need more power, if it is stock there is not much point in upgrading. we have a amps calculator on our site, you can use 14 volts and enter watts from lights, stereo, and so on. http://www.rushps.com/tools.html
Click to expand...

Gotcha. I put the stock 90A back in. I have a spare bracket that I can mess with if I want. Good question, I have no clue so I'll check out your link. I have two amps, two sets of offroad lights, upgraded headunit, etc.

Thanks!
 
Its your amps and lights you need to look at, head unit will not pull much more power than stock. an easy, although not as accurate is to add up all your additional fuses. you want to overshoot by 25% to keep the alternator from running at full power, so a 125 amp alternator on a 100 amp load.
 
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