Alternator failure after rebuild. Please help?!

This happened to me, with an alternator which was rebuilt with Regitar parts successfully twice....got 10,000 miles out of each rebuild, and then the third rebuild didn't take. It turned out to be a failure of a tiny wire in the alternator body itself. Most alternator shops can fix this easily, but you need to tell them that you suspect the wire failure, and then they'll check that before anything else.

I have not yet gotten a bad set of parts.

Also, carefully check the screws that hold the voltage reg and the brush carrier to each other and to the alternator frame. You'll know if they were loose, because you'll see evidence of arcing. This also happened on one of my rebuilds; tightened the screws and all was well.

Also, check your brushes.

 

I had a similar experience with my F355. I ended up having to rebuild it three times within a year and finally overcame the problem when I took out my aftermarket radio. Something in the audio system was causing the alternator to malfunction. Haven't had any issues since (12 months now). So it may have something to do with another part of the electrical system. I also installed a digital voltmeter on the dash for peace of mind.

Good luck, Henry

 

I and a friend both had failures with Regitar voltage regulators in our Nippon Denso alternators in our F355s. I would try to source factory ND parts instead.

 

You can order brushes from Nations Starter and Alternator (they're on the web), and I've also seen them on eBay.

I'm getting ready for work/getting my son started for the day. I will take a few pictures of the area after 7pm and post pictures. The small wires are what connect the coil to the rectifier studs, and they can fail eventually due to heat/vibration. Also, the main coil wires can fail as well, but this is pretty rare.

It does appear that you have a heat problem. I bought a better quality Voltage Regulator from O'Reilly Auto Parts which has a lifetime warranty. I've had it in for 6 months now, so no long-term data yet. It cost $75, and I'll post the part number when I get home from work.

 

Try installing a Denso regulator part number 126000-0400.

I haven't installed or tested it on my car yet, but it is sitting on the shelf in case I need it. My alternator is still holding up well after 7 years since I rebuilt it.

 

My stereo was in the car when I purchased it, but was also an older Alpine. I only replaced the rectifier and regulator on each rebuild as the brushes looked fine. Even though the stereo was a high dollar/high quality installation, I think the guys just arbitrarily look for ground/power sources for the radio and don't consider what other things that circuit has to power in the car. I have since installed a heat shield and ceramic coated Fabspeed headers as well.

Henry

 

I would add (from my short experience working at Delco Remy - alternator company):

*Check the diode trio.

I would venture a guess that the trio may be a culprit. Sometimes it fails because it is not heat-sinked properly or connected well electrically and I actually think it fails more often than the regulator as the trio/rectifier is seeing really high currents so this is the stressed part in the system IMHO.

People usually suspect regulator but they forget to test the diode trio. Remember that the trio is actually 6 diodes (3 for the + side and 3 for the - side of the rectifier). These diodes are usually press-fit into some casting for cooling. If they are not bonded well, they will overheat and fail. Same thing for making sure that they are connected well electrically.

 

Yeah.

I bought a USI regulator (currently in my alternator) for a fellow brother and while I was at the shop had a discussion with the guys there. They told me that the Denso regulator is what FAA mechanics almost always request. The funny thing is, it's a Denso alternator so WHY didn't they use a DENSO regulator in it in the first place?!?!?!?!?!

Only Ferrari I tell you, only Ferrari.

Anyway, I'm running the USI regulator in my car and it has held up for 7 years, and I have the Denso sitting on the shelf should the time come to rebuild it again.

 

OOOOO!!!!

Nice tip Bart, good looking out bro!

 

The O'Reilly part number for the regulator with lifetime warranty is 29-0188. Cost when I purchased it was $73.99. It's been on the car for 6 months, so, as I mentioned, I don't have long-term data yet.

Also, wires to check are on the rotor, and if you pull the diode and look in the cage you can see them. This requires a qualified alternator shop to fix.

If you buy the regulator and install it, have O'Reilly check the alternator before you install. They will ask you what alternator you're testing; just tell them it's from a 1991 Toyota Celica.

 

Yup.

http://www.usi.com.tw/pdf/car/Denso_Regulator.pdf

 

On the F355, a stereo (or any load) needs to be attached DIRECTLY to the battery.

The reason for this, is that the "sensing wire"* also attaches directly to the battery. If you take a load AFTER the sensing of the load, things start to get wonky.

If you peel back the black insulation from the stock terminal, you will see a little red wire parallel with the fat red wire. This little tine wire goes aaaaallllll the way back to the regulator in the alternator.

Changing the positive terminal, like a lot of stereo shops routinely do, can upset the Italian balance of the "sensing wire*".

*Ferraris words not mine

 

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