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Kootch27,

I talked to the Generator repair person today after he disassembled the alternator. The stator windings were in bad shape and needed replacing. The commutator was shot, also. Finally, all the rectifiers were bad! He will send out for the new stator winding and do the remainder of the replacements when he has the parts. Total cost is $225 which I thought was reasonable even though a rebuilt one from Rock Auto was more like $125 (but they were the wrong ones). Since they have had none in stock for 9 months or more I'm not looking for a "deal" at this point. It is still snowing around here so I would not be driving the car for another week or two anyway. I liked your idea but I was a little concerned that you only had two months of "running" time on it so far and several previous disappointments. I wonder if the 4A-GE alternator regulator is more susceptible to the exhaust heat from the supercharged engine? That might explain why Toyota moved the voltage regulator to the trunk in the Supercharged 4A-GZE engine. I will install the alternator next week when I pick it up and run the voltage regulator tests if there appears to be a problem. My next job will be installing the distributor repair kit to eliminate the oil leak problem (for awhile, anyway). I have the Toyota Repair Manual that I bought when I bought the car in 1988 and saw the test procedure but I thumbed thru the entire book yesterday trying to find the voltage regulator and never found it! Thanks again for all your help. I tried to find a new voltage regulator online but could not find one in the event I need one. I saw one some time in the past few months but can't seem to re-locate it so if you know where I can purchase one if I need one I'd appreciate that information. Looking forward to Spring which is very late in arriving this year. Living in Minnesota, I was almost hoping for "climate change"!
 

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Hi Wayne,
I think that's an acceptable price for the custom rebuild. I hope they have a warranty on the parts & labor. What I like is that yours will still be the same original alternator, just rebuilt, when this is all over.

Yeah, you raise a good point. The two months of 'running time' I mentioned hasn't even really been two solid months. Before my alternator took a dive, this car was my daily driver. I ended up picking up another car to serve as my transport (plus I definitely needed a 4-seater) while I fixed this one. Anyway, my MR2 has become by my spare car so it doesn't even get driven as much as before the alternator failed. On top of that, my normal driving distances are actually quite short -- kids' school or work, which are both within 10 miles of home. IOW, I don't think I'll expose the alternator to sustained periods of heat in its typical duty cycle for me.
But otherwise, I agree -- I believe that the VR was mounted remotely for this reason. The alternator really does sit next to the exhaust manifold. I also understand that the original 4agze alternator had a heat shield which was pretty much a second back plate that was mounted on extended bolts to the actual back plate of the alternator. Mine was missing this heat shield although it still had the extended bolts on it. I think a mechanic who worked on it in the past didn't bother to put it back on :(. Wrapping my exhaust manifold with header wrap or fabricating a heat shield out of aluminum sheet might help. It's a 'someday' thing.
All that said, I have only anecdotal evidence to the longevity and reliability of these 4age alternators used on the 4agze engine. There are stories representing both sides of the issue - some say it's fine, some say it won't last long. Looking at the 4age, 1zz-fe and the 2zz-ge motors, the alternators are on the intake side, so I'm pretty sure that heat was a consideration for the remotely mounted VR.
As far as new VRs for the supercharged MR2, I am not sure if you can find one anymore. Your best bet would be Ebay and 'For Sale' posts in other Toyota Forums that feature cars that had the 4agze engine. Some have gone to the Honda equivalent, and MR2Tim, a veteran member here also has gone full old-school mechanical VR, which I considered doing at some point. I even found a mechanical one that I suspect is plug-n-play (at least its connector size/shape and pinout appear to be the same as our IC-based VR). These were ones used in the older-generation Toyota 3K and 4K engines of the 70s and early-mid 80s. Or you could go with the 4age alternator with the built-in voltage regulator like I did.
Which brings me to my last thoughts on this -- I was thinking of remotely mounting the IC voltage regulator to the same mounting spot as the external VR. I think it's only a matter of extending the three internal terminals out to the trunk. I think it can be done. The 'unknown' here is that this is how it was already done with the original alternator and original/stock external VR, but that it needed the internal read wire to do some middle-man/translation between the alternator and the VR. My thought is that whatever the role of that read wire is now integrated into the internal VR of the 4age alternator, so it may be able to operate without it. I'd like to experiment with it when I have some free time to. Or maybe when my current 4age alternator fails due to heat then I'll be forced to experiment and find out :).

I'd like to hear how your rebuilt 4agze alternator performs when you finally get it back!
 

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Hi Kootch,

You asked me to reply once I changed out my defective alternator. I removed it (with considerable difficulty) and took it to a local rebuilder. He had the stator winding rewound because it appeared to be nearly fried though he admitted it still seemed to work. He also replaced the commutator, brushes and rectifiers for $250. After reinstalling it and worrying about whether the regulator would also need to be replaced, I was relieved to see everything working! I then found a local repair shop to rebuild the distributor. The O rings were brittle and cracked. I replaced the rotor and distributor cap at the same time. Only problem I now have is the oil pressure meter is not working. I suspect I accidentally disconnected the wire from the pressure transducer when I was removing the alternator as there was a wire with a slide type connector hanging down that I could not identify where it came from. I can live with that. It has been about a month and so far, so good.
 

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Hi Kootch,

You asked me to reply once I changed out my defective alternator. I removed it (with considerable difficulty) and took it to a local rebuilder. He had the stator winding rewound because it appeared to be nearly fried though he admitted it still seemed to work. He also replaced the commutator, brushes and rectifiers for $250. After reinstalling it and worrying about whether the regulator would also need to be replaced, I was relieved to see everything working! I then found a local repair shop to rebuild the distributor. The O rings were brittle and cracked. I replaced the rotor and distributor cap at the same time. Only problem I now have is the oil pressure meter is not working. I suspect I accidentally disconnected the wire from the pressure transducer when I was removing the alternator as there was a wire with a slide type connector hanging down that I could not identify where it came from. I can live with that. It has been about a month and so far, so good.
Thanks for the update, Wayne. Sounds like great news!
From what you describe, it doesn't sound like they didn't remove, replace, or did anything at all to the read wire in your alternator, which sounds very encouraging to me.
I will get around to restoring mine too one day, as I think mine failed in exactly the same way yours did. I have a strong feeling that my read wire is actually still good and it's the stator and rotor windings that have fried from the past oil leak from my alternator, just like yours.
My NA alternator has been holding up just fine since my last post. Like I say .. I don't drive it as much as I used to when it was my daily. And even then, my driving distance is only around 10 or 11 miles round trip. I actually took my mr2 for it's first 'long' drive since installing the NA alternator -- about 50 miles round trip, mostly freeway. No issues and nothing noteworthy. I have a feeling that it will be a long time before I have to address this issue again. But I'm very happy to hear from you that it is possible to get the SC alternator restored for a somewhat reasonable price. I hope it gives you many many more miles and years of enjoyment. Thanks again for the update!

PS - Yeah, the single-wire connector is the Oil Pressure sender wire. It's a black wire with a slide-type connector. Altogether, there were 5 wires I had to keep track of during disassembly/reassembly -- two for the AC compressor, two for the alternator (one of them being the heavy gauge B+ wire, and the other was the three-wire cable to the round connector), and the last one is the oil pressure sender wire. IIRC, the oil pressure sender itself sits on the side of the block between the AC compressor and the alternator (at least that's where I seem to remember the wire was coming from and where the connector from the harness side connects to. Maybe check it out when your mr2 is due for its next oil change? :)
 
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