My otherwise faithful 1989 240 has developed a little problem and I hope someone experienced can give me a little help. At higher speeds on the highway, the little red battery light begins flickering and after a few minutes, the gauges also begin to go dead and the car starts to sputter. If I slow down immediately, power is restored, the gauges re-enliven and the sputtering stops. It will then run fine for a few minutes and then aforementioned cycle will begin again. On city streets with stop signs and lights, it runs fine. The problem is on the highway. The battery does not discharge when all this is happening but the electrical power begins to fade at consistently higher speeds until I slow down or stop. I suspect a voltage regulator issue or possibly a short? It is obvious the alternator is charging the battery but something is interfering with the electrical system at higher rpms. Any ideas from you electrical troubleshooters? Denis in Tucson, AZ

Phil could be right about the brushes. An easy fix with a new part. Also easy to remove to check them.

Also I would check the belt tension and clean the connections to the Alternator and around the positive cable.
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89 240 wagon, 94 940, 300K, 94 940, 141K

Thanks for your comment. The belts are tight so Phil probably is correct in probably cause. Part is reradily available here in Tucson and I will r & r soon. Thanks for your help. Denis V

Hi,

It’s is most likely to be the carbon brushes are getting to short, for the springs that hold them in place, to keep enough pressure on them at high engine speeds.
That much wear usually leaves a lot of carbon dust in the wrong places and they become sticky.

Also another phenomenon that occurs due to worn brushes is that the slip rings, that the brushes run on, go slightly out of round and this can cause the brushes to bounce a little bit.

When the brushes lose proper and continuous contact current output varies even at low speeds so basically you are headed for more trouble if you do not service the alternator soon.

During a night time trip your lights headlights might occasionally flicker upon startup.
It’s an old white man trick borrowed from the red man, that to use smoke signals, to tell the white man that his worse troubles were on the horizon!

(:-)
Phil

Phil, thanks a lot and your explanation makes sense in relationship to the symptoms. I suspected it had something to do with the voltage regulator and appended brushes. I will order and install same forthwith. Sage indian advice well taken--I won't operate vehicle until I make the repair. Denis V