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Need tips : 97 Olds voltage problem.

97 Olds 88 100K miles.

I noticed last night that my headlights are flicking to a lower power then back up when cruising at speed. Does it many times per minute. If I go uphill and it shifts down to 3rd, then the lights go dimmer and only come back up to full bright when it shifts back into 4th and the motor load reduces.

One of those times the voltmeter light came on very briefly. Am I looking at a bad alternator, or voltage regulator ( is it inside the alt ? ).

I put in a new alt 2 yrs ago, maybe 20K miles on it. I backed off the batt post bolts then retightened, no change so I Know its not the batt ( shows green in window).

Any suggestions appreciated, I have a digital VOM, maybe I can check something if any ideas. TIA

Stumped in Canada

Reply to
PDT
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Could the belt be slipping?

Reply to
Silver Surfer

"PDT" wrote

97 Olds 88 100K miles.

Lights dim when engine revs. Lights brighten when engine slows. Any ideas. TIA __________________________________________

We have seen this problem in these situations:

  1. Alternator belt is loose, slips more when revving. Tighten belt.

  1. Alternator slip rings or brushes are dirty. a. Replace alternator. OR b. Spin alternator and insert pencil eraser to clean slip rings. OR c. Partially disassemble alternator, clean slip rings and brushes with sandpaper. Replace brushes if bad.

  2. Internal alternator regulator is failing. a. Replace alternator. OR b. Partially disassemble alternator and replace regulator.

Good luck.

Wendy & John. ________________________________________

Reply to
Wendy & John

I had similar symptoms on a similar model GM car. Inside the alternator, there are three sets of rectifier diodes. Normally, all are working, and you get good alternator output, the DC is moderately pure, and it works. If you blow out one set, then you get slightly lower alternator output, the DC is noisy and varies more, and it is working halfway. At this stage, some drivers notice it and some do not. Then, if you blow out the third set, the alternator is still putting out DC, but it is much reduced and very noisy. Batteries often run dead.

I suggest that you have your alternator checked out, which is part of a _good_ electrical system test. If you go at it with simple meters, you may not see the AC riding on the DC, and you might miss it.

---Bob Gross---

Reply to
Robertwgross

Thanks, should be easy to find now.

Reply to
zz1200

Thanks everyone, good tips.

Reply to
PDT

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