Overdriving alternator, low rpm charging
04-23-09, 10:03 PM
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Overdriving alternator, low rpm charging
I've been chasing electrical problems ever since I got my '92 SC4. I've cleaned all of the grounds under the engine bay and all of the ones I can find under the dash, and I even replaced the alternator wire and some of the grounds under the hood with some leftover 4ga wire left over from an old install in another car. The "big 3" under the hood usually eliminates electrical problems, but not for this car.
When the car decides to run (it has a random no-start condition), it charges fine except for at idle. I took the alternator to a local rebuilder, and he replaced the rectifier, voltage regulator, brush/holder with brand new parts and also put a new slip collar under the brushes (cost less than 100$ FYI). I put the new piece back in, and everything still dims big time at idle. Idling in gear with the brake on and not moving, the engine will idle between about 500 and 550 rpm (verified through a scanner in the OBD port + an autometer tach).
The alternator rebuilder suggested to find a smaller alternator pulley so the alternator is a little overdriven at idle. If that doesn't work, then it will need to be rewound.
Does anyone know the stock diameter for our alternator pullies? What about shaft diameter? I have found many places to buy alternator overdrive pulleys for all kinds of GM and ford cars, but nothing for toyota/lexus.
When the car decides to run (it has a random no-start condition), it charges fine except for at idle. I took the alternator to a local rebuilder, and he replaced the rectifier, voltage regulator, brush/holder with brand new parts and also put a new slip collar under the brushes (cost less than 100$ FYI). I put the new piece back in, and everything still dims big time at idle. Idling in gear with the brake on and not moving, the engine will idle between about 500 and 550 rpm (verified through a scanner in the OBD port + an autometer tach).
The alternator rebuilder suggested to find a smaller alternator pulley so the alternator is a little overdriven at idle. If that doesn't work, then it will need to be rewound.
Does anyone know the stock diameter for our alternator pullies? What about shaft diameter? I have found many places to buy alternator overdrive pulleys for all kinds of GM and ford cars, but nothing for toyota/lexus.
06-29-09, 05:18 PM
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I'm not in a position to take the one off of my car and measure the shaft, so I'm gonna assume the shaft on all Denso alternators is the same.
Does anyone know the OD of the stock alternator pulley? I can get 6 rib ND pulleys for dodge magnum engines in all kinds of diameters, so I can use that if I know the shaft on all ND alternators is the same.
Does anyone know the OD of the stock alternator pulley? I can get 6 rib ND pulleys for dodge magnum engines in all kinds of diameters, so I can use that if I know the shaft on all ND alternators is the same.
07-01-09, 03:45 PM
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Yeah, that would be perfect!
95silver, I've had to buy 3 new batteries for this car since I've owned it in Jan. The most recent battery was purchased new around the end of May and it's already starting to drag a little bit on startups now. The car used to have a bad dimming problem, but new grounds and a "big 3" underhood wiring upgrade fixed that except for when all the headlights and accessories are on idling in Drive.
I called some alternator/starter shops that are local to me, and none of them had any specs because the pulley and rotor are "dealer only" items that they don't stock.
I did some number crunching/searching on This site and found other ND alternators that use the same nut for the end of the rotor... and those alternators all have a 17mm shaft. I had to do the same thing on my '96 dodge (with a ND alternator) and the shaft size on it was 17mm also. Going by the assumption that the shaft is 17mm, This pulley should fit on the shaft with about .020" press fit. The only thing I'll need to find out is if the spacing is the same. If it's less, I can use a washer to space it out, but if it's too far out I'll have to cut some off the back of it to sit back some.
95silver, I've had to buy 3 new batteries for this car since I've owned it in Jan. The most recent battery was purchased new around the end of May and it's already starting to drag a little bit on startups now. The car used to have a bad dimming problem, but new grounds and a "big 3" underhood wiring upgrade fixed that except for when all the headlights and accessories are on idling in Drive.
I called some alternator/starter shops that are local to me, and none of them had any specs because the pulley and rotor are "dealer only" items that they don't stock.
I did some number crunching/searching on This site and found other ND alternators that use the same nut for the end of the rotor... and those alternators all have a 17mm shaft. I had to do the same thing on my '96 dodge (with a ND alternator) and the shaft size on it was 17mm also. Going by the assumption that the shaft is 17mm, This pulley should fit on the shaft with about .020" press fit. The only thing I'll need to find out is if the spacing is the same. If it's less, I can use a washer to space it out, but if it's too far out I'll have to cut some off the back of it to sit back some.
07-01-09, 04:14 PM
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I went out just now and slipped the belt off and measured the pulley OD at the ribs as good as I could by snaking a caliper down in there, and got a few thousandths less than 2.1". The pulley I linked to is 1.7" OD, so that would raise the alternator rpm about 400 rpm with the engine at a 650rpm idle. Do you think this is enough to make a difference?
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07-01-09, 05:16 PM
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I found the pulley off of a 1997 LS400 on that site, http://www.wai-wetherill.com/product...i_num=24-82263
It looks like it does indeed have a 17mm shaft. When compared to the stock GM alternator pulley that I linked to the summit overdrive version earlier it looks like all I will need to do is find a .050" thick washer and bolt it on!! Both (in stock form) are apparently 57mm diameter with a 17mm bore, only the spacing is different. http://www.wai-wetherill.com/product...ai_num=24-1272
It looks like it does indeed have a 17mm shaft. When compared to the stock GM alternator pulley that I linked to the summit overdrive version earlier it looks like all I will need to do is find a .050" thick washer and bolt it on!! Both (in stock form) are apparently 57mm diameter with a 17mm bore, only the spacing is different. http://www.wai-wetherill.com/product...ai_num=24-1272
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