[Andy4639]

Originally Posted by dmjlambert

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.

No it's not normal! It's a condition of the system in these trucks. The head light relay addition is a great way to get better working lights. It takes all the load off the whole wiring system. In turn it makes the components last longer like head light switches ignition switches dimmer and any other component.

The problem is you are way over loading the system.
Even if you buy the biggest battery you can it want help. Yes it will play longer at Idle before it quits but it will do the same thing because at 12.5 volts your using more than you are making.
If you are still using the original regulator system then I suggest the upgrade before doing anything else.

To fix it if it where me:
Buy at least 140 alternator with internal regulator Min and install 2 batteries.
Hook them up in parallel which will be 12 volts but double your amp hrs which in turn will run longer.