LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Speedometer works intermttently

Old 04-16-12, 12:55 PM
Join Date: Feb 2004
Location: North Carolina
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Originally Posted by fixmiester View Post
I actually took my alternator out a few years ago, because I was SURE it was causing a low battery voltage problem, after making dozens of measurements. Guess what? It turned out to be an intermittent bad cell in my 1-year old battery. Boy, was I mad at myself, because that's a lot of work. With over 100k on the car, I figured I should at least replace the brushes while I had it out, so I took it apart. Brushes were only 30% worn, and they are hard to find, so I just put them back in. The reason I mention all this is because I see several posts about how leaking ATF has ruined so many alternators. The Denso alternator is extremely well made, and it is much more likely that the fluid has only contaminated the brushes or slip rings. I would bet that you can simply clean any gunk from the brushes and the inside, maybe polish the slip rings with very fine sandpaper, put it all back together and get it tested for free at one of the auto parts places. AFAIK, there is nothing else in the alternator that would be impacted by any auto fluid; windings and diode packs should not be phased by it (unless it gets so clogged with debris that it overheats). It's certainly worth a shot.

How did you determine the battery had a bad cell? I'm having issues again that I think is due to voltage, but I hate to pull out the alternator I just installed last year if I don't have to.

Last edited by Live4brew; 04-16-12 at 01:09 PM.
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