Kingman Posted November 23, 2009 Share Posted November 23, 2009 (edited) I installed a new 90 amp alternator for a 1993 SOHC Maxima. I ran into the problem of the V belt pulley rubbing on the casing of the alternator, so I cut a piece of brass pipe to fit as a spacer and it worked fine. I also had to grind the tensioner bracket down a little to fit the casing better. So now I have a weird problem. When first starting it up, it didn't charge at all. Lights were dim, voltage at less than 12V. however, at exactly 3300 rpm the voltage jumps up to normal and the lights brighen up, and brighten up a lot. Definitely an extreme improvement. If I turn the truck back off and re-start, the voltage drops to 12 until I rev it again. Then it charges perfectly fine, even at idle, until I turn it off again. Weird? The Pathfinder pulley isn't very much smaller than the serpentine belt pulley it originally came with meant for the Maxima. All the connections are good, tight, and clean. Any ideas? Edited November 23, 2009 by Kingman Link to comment Share on other sites More sharing options...
nunya Posted November 23, 2009 Share Posted November 23, 2009 Your still charging a battery you juiced a bit driving on the bad alt. You load test the battery to make sure you didn't hurt it? Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 Your still charging a battery you juiced a bit driving on the bad alt. You load test the battery to make sure you didn't hurt it? The battery is fine, 12.6V as usual. The new alternator is simply not charging at all unless I rev it up and then it's like someone flipped a switch and everything brightens and it starts charging. I tried not revving it after starting and the voltage continued to drop, as if the truck was running off the battery and not the alternator. Link to comment Share on other sites More sharing options...
MY1PATH Posted November 23, 2009 Share Posted November 23, 2009 (edited) x2 on worn out battery but also consider; the pathfinder pulley may not be much bigger but is the maxima balancer bigger? this would turn the alty faster than a pathy i it has a smaller balancer. Going from a 3" pulley to a 2.75 or even 2.5" will make a huge differance. In the case of my ford aly I had to have pulley machined to 2" but I doubt you will need one that small. If you have the older 2 piece pulley you can try putting a thin washer between the halves to get the belt to sit lower in the pulley that would possibly be the equivalent of a 2.75" Edited November 23, 2009 by MY1PATH Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 I swapped batteries with my dad's truck, no difference at all. I was hoping it was that simple. I see what you mean about the pulley. But wouldn't the charge be relative to the RPMs with an incorrect size pulley? Shouldn't the charge increase as you rev and then drop back down when you idle down, not suddenly start charging at 3500 and then charge consistently at any RPM? Or is the different pulley tricking the regulator? It also charges higher than 14V when it starts charing. It charges at the next line up, 16V. Seems like a regulator issue? Tomorrow I'll put a washer in between the 2 halves of the pulley and see what happens. Also, if I do need a smaller pulley, I can't seem to find one. I went to 2 auto parts stores looking for pulleys and they said they didn't have any. Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 Also, my subwoofer is going thump every time I turn the key to on. It never used to do that before. I'd rather not fry my amp... Link to comment Share on other sites More sharing options...
nunya Posted November 23, 2009 Share Posted November 23, 2009 Might have got a defective alt. Wouldn't be the first time I've heard of defective new parts. (Heck one time with a Ford Contour since we are talking alts., went through 4 new ones before getting one that actually charged) Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 I hope not! I tried calling NAPA but they close super early on Sundays. Link to comment Share on other sites More sharing options...
MY1PATH Posted November 23, 2009 Share Posted November 23, 2009 (edited) the deceptive thing about alty's is they usually give you engine rpm ratings for the pulley configuration and engine they were built for. You want to try and match the same Alternator shaft RPM in an entirely differant build. here's my theroy so 3500 the chaging sytem turns on and it stays on to keep supplying power (say if there was a dip in the idle or a near stall it kept your ignition going) even tho it wasn't designed to run that slow (shaft rpm) for prolonged periods.... edit; I ran some pulley calculators to figure out charge cut in @ lower rpm. the numbers are engine rpm, balancer dia, pulley dia & shaft rmp 3500 6:3 7000 3209 6:2.7 7000 2916 6:2.5 7000... 2333 6:2 as you can see the numbers don't get low enough to put the cut in @ the idle range. the short version. I think I'm wrong, the pulley may not be the problem maybe take the alty back and have it tested. Edited November 23, 2009 by MY1PATH Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 So it could be designed to turn on at a certain RPM? You said you had your pulley machined, what kind of place did you take it to and what exactly do you mean by that? Link to comment Share on other sites More sharing options...
MY1PATH Posted November 23, 2009 Share Posted November 23, 2009 Using a lathe I hade one made smaller. Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 Drove up to the store to get gas, and I noticed I now have more power. Not much more, but very noticeable. I wonder how long until my transistor fries. My amp is going nuts as well. The sub barely beats at all now, but the green power indicator light is on. Hope I didn't blow it... Tuesday is my next day off. I plan to exchange my alternator for a new one, hopefully it's the culprit. Leaving the gas station I hit the gas and made a few people jump and glare at me since it was under the cover still. Link to comment Share on other sites More sharing options...
nunya Posted November 23, 2009 Share Posted November 23, 2009 You have to reset you radio presets and settings man, you DID disconnect the battery during the switch...right? Link to comment Share on other sites More sharing options...
JesseLivingston Posted November 23, 2009 Share Posted November 23, 2009 (edited) You have to reset you radio presets and settings man, you DID disconnect the battery during the switch...right? I hope you also purchased the proper voltage regulator to go with the new higher current alternator? Yes they most certainly are designed to run at a certain RPM. It's a generator after all. You would have to adjust pully size to get it all working properly. Edited November 23, 2009 by JesseLivingston Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 (edited) They are an internally regulated alternator, and yes I did re-set the settings on the deck after connecting the battery. The amp is probably blown from the voltage spike since it thumped so damn hard and won't make any noise now, so if it is bad then I suppose NAPA should be replacing that as well for providing a faulty alternator. I checked the fuses and they are still good, just no noise from my sub. So in comparing the 2 pulleys, the outside diameter of the V pulley is slightly larger than the PV pulley, however taking into consideration the pitch of the V and where the belt contacts there really isn't any difference to speak of between the two. I just don't see how that minor of a size difference can be the difference of 900 RPM and 3200 RPM. I don't see any reason for an alternator not to turn on until that high of an RPM. Edited November 23, 2009 by Kingman Link to comment Share on other sites More sharing options...
adamzan Posted November 23, 2009 Share Posted November 23, 2009 I believe Simon has the same issue as you. Saw him post about it somewhere. Link to comment Share on other sites More sharing options...
MY1PATH Posted November 23, 2009 Share Posted November 23, 2009 you saw my math results, it doesn't add up. 3500 rpm to set it to charge means 7000 shaft rpm. thats just not right. In order to aqire that shaft speed @ idle you would need a .75 pulley (impossible) or a larger balancer(also not very likely to happen) Link to comment Share on other sites More sharing options...
Simon Posted November 23, 2009 Share Posted November 23, 2009 Yep, mine does the same. At 2700RPMS mine starts to charge, then, at idle, after hitting that RPM once, it charges fine. Anyways, I'm going to look into a smaller pulley, but haven't been able to get the measurements on mine yet. Link to comment Share on other sites More sharing options...
MikeV Posted November 23, 2009 Share Posted November 23, 2009 That just sounds like a bad Voltage Reg. in the alternator; I've been running a maxima alty with no issues for a while. Link to comment Share on other sites More sharing options...
Terrano1992 Posted November 23, 2009 Share Posted November 23, 2009 x2 for bad voltage regulator. It's possible that Maxima's and Pathfinder's VR are interchangeable (until both alternators are Hitachi, LR190 and LR170). But I can't say this with full confidence. Link to comment Share on other sites More sharing options...
Kingman Posted November 23, 2009 Author Share Posted November 23, 2009 I tested the alternator in class today, absolutely no charge until 3200 when it clicks on. When it does, it spikes to 16.1V then settles down to 14.5V then creeps to 15V then 15.5V and levels off. My shop teacher's eyes about popped out of his head when it clicked on and spiked like that. Link to comment Share on other sites More sharing options...
GrimGreg Posted November 23, 2009 Share Posted November 23, 2009 Guess I might go get my J-yard one checked out at the Zone before swapping it in. Link to comment Share on other sites More sharing options...
Simon Posted November 24, 2009 Share Posted November 24, 2009 Mine was brand new when installed, not reman. It's done it since day one, as did the previous Max alty I had in there (which was used). Mine never goes above 14.4, no matter how high I rev. Link to comment Share on other sites More sharing options...
MY1PATH Posted November 24, 2009 Share Posted November 24, 2009 it should Never break 15v! Link to comment Share on other sites More sharing options...
adamzan Posted November 24, 2009 Share Posted November 24, 2009 Mine was brand new when installed, not reman. It's done it since day one, as did the previous Max alty I had in there (which was used). Mine never goes above 14.4, no matter how high I rev. Not to go off topic but where did you find a "new" alternator in ontario? All I could ever find was rebuilt @!*%. Link to comment Share on other sites More sharing options...
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