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Old 01-09-2019, 07:44 PM   #7
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Join Date: Apr 2016
Location: Cypress, TX
Posts: 1,458
Re: Dimming lights, altenator or battery?

I have a new CS144 alternator in my truck, which is what they put in 1993 C1500 Cheyenne trucks, Optional Heavy Duty 124 Amp. It is a more modern model than 12SI alternator. I have no radio and only significant draw are from plain stock headlights, the A/C blower motor, and the GM HEI distributor. I have not added a relay to the headlight wiring, it is a plain stock setup. The headlights are noticeably dimmer at idle, such as when I stop at a stop light or stop sign. The same thing was true when I had a 12SI in it, and the only reason I replace the 12SI is because the bearings were wearing out. I believe this lower output voltage of the alternator and dimmer headlights at the lowest RPM of the engine is normal. I would not try to fix it unless the problem was severe.
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