Repairing alternator

Disassemble your alternator and rerun your tests. Brushes worn close to the "dot" are done. Also, both the stator and rotor must have a few ohms resistance. Not too much, and certainly not zero. Same with stator.

Hi Philip,

Thanks for responding.

That "dot" you refer to, is it a little round cavity on the side of the brush? If it is, there is a little less than half of it left... however the Haynes manual says that the brushes can go as low as 0.06" albeit it is hard to believe they will reach the rotor when so short...

Related question: Do Toyota dealerships sell things like brushes for alternators or should I go somehwere else to get them?

/Mikhail

however the

BINGO!!!! Replace the brush set/holder. Dealer item for about $20. Don't both trying to repair it.

While you're at it you should probably also replace the bearings as they probably have about 150K miles on them. Any auto electric shop could do this inexpensively. Saves removing the pully and pulling or pressing the front bearing.

Steve

If it is producing 11 volts it is probably faulty in the regulator or the primary circuit. I would make sure the brushes are contacting the slip rings and that there is continuity through the slip rings to the winding. If all seems ok there then investigate the regulator. You may be able to bypass the regulator and see if the output increases.

Replace the brushes

On all alternators I have worked on, (although I have not worked on a Toyota alternator), there is a way to bypass the regulator and apply full power to the fields. If you do this and the voltage goes up (ie. varies with the speed of the alternator without ever being regulated to 13.8v) then it is almost certain that the regulator is shot. The regulator is my best guess, and while you're at it I would replace teh brushses. They're not that expensive, and it saves you from going back in later to replace the brushes.

corresponding

Evil.... you need to familiarize yourself with Nippon Denso alternators. Hot circuiting any alternator rotor when the brushes are shot will give you a false failed regulator diagnosis. Furthermore, when brushes are barely contacting either slip ring, a continuity test of the rotor via the brushes may show good on the bench but go open (or increased resistance) with the rotor in operation. Result is marginalized output.

Use it as a core at Pep Boys for a new alternator and get their lifetime guarantee alternator. I've done that and got 3 alternators for the price of one so far in the long history of my 1985 2wd Toyota Truck!

Replaced the brashes, dealer didnt have the holder in stock, so I had to use a soldering iron, which is not a big deal for me. Well, the thing still doesn't work. I took it to Canadian Tire to test, they said it was dead. I didn't believe them as they are usually not very good at service, so I tried it in the car anyway. The guys were right this time... So, what's next? Regulator?

/Mikhail

While you had the unit apart, did you have 3-5 ohms resistance between the slip rings and .... no continuity from either slip ring to ground? Same resistance between any two segments of the three stator segements and .... no continuity to ground? If so, AND you are sure the Alterantor fuse is not blown, then by deduction you need to replace the regulator/rectifier assembly. Price the part first because a rebuilt exchange unit from a parts house may cost about the same.

To conclude the story, I priced the regulator at a Toyota dealer - $260 CDN (roughly $190 US )!!! They had the whole alternator for $330 CDN or something close! So, I took the thing to an electric shop where the guy rebuilt it for $120 CDN. He said the stator was bad and showed me my old stator with darkened wires in spots and the regulator was bad too. I am not sure if the stator was really that bad as it measured OK, but I am not complaining after having looked at the Toyota price :)

/Mikhail

Stator was fine, he just didnt want to tell you it was only brushes, it doesnt pay as well. Stators dont fail in ND's!

I don't think you followed the thread. I changed the brushes myself before bringing it to him. I think the real problem was the regulator but he did changed the stator too...

/Mikhail

Exactly what I was saying. Catching on quick Mick!

MDT Tech® , being of unsound mind, did utter in news:sI_nb.7607$ snipped-for-privacy@newsread4.news.pas.earthlink.net:

There is ONE exception, an exception that is extremely common in the Rust Belt.

Corrosion can and does cause the stator to short out, requiring replacement of the stator. The less the car is used, the more corrosion builds up on the stator, eventually bridging the gap. I have seen this personally with the ND in our old MR2.

This was explained to me by the rebuilding place in my small town. These are the same guys that sold me brushes for $5 so I could fix my Integra's ND myself.

OK Tegg, I'll buy that. I should of said "they dont ever fail in my salt free area. ;-)

I'm intrigued by the thought that nobody offers a potted stator! Think of the implications though. Hmmmm.

Better yet, they sell the whole brush assembly for $19 (at least for my Tercel). Saves having to solder in new brushes.

-Ted