Like alot of you i have had this issue day one on owning the Jeep, you are in drive, at a stop and with the headlights/fogs on the Jeep simply cannot get enough voltage/amperage to the accesories/lights/turn signals are slow. Switching to a bigger alternator didnt fix it, going to a huge battery didnt do anything, upgrading and replacing the power/negative wiring didnt do anything.
My wagoneer has a 90 AMP alternator on it brand new within the last year, and the old one did the same which was a 76AMP i think ? somewhere around there, and with the engine at 600 to 650rpms in drive the alternator simply cannot get the voltage needed to the headlights, blinkers, fogs and blower motor, and the volt meter on the dash shows it well under the 13v line. I tested the voltage at the battery and it shows well over 13.5v but down the chain it drops. If i crank the rpms up to 750 or so idle then i have no voltage issues with the headlights/a.c on, its always right at 13v and the blinkers are blinking fast and the headlights arent dim. It gets worse when the a/c is on, with the compressor on the rpms drop about 50-100rpms and power is redlined. So i need to keep the engine idle higher to compensate
I dont think the alternators im using can supply enough power/amps to the Jeep at lower RPM's. The problem with keeping the RPMS at 750 in drive, is when i go to park its above 1,000 rpms. Around 1100. If i drop it down to 600-650 like it should be in drive, in park its around 900 rpm. Also when the rpms are too high above 1000, the engine will diesel on me when i shut it off, which you never want to happen. So im stuck, keep rpms lower where they should be so it doesnt diesel and simply rev too high in park, or keep them higher so i dont have power issues. I cant keep the rpms higher, which fixes the issue.. I dont want the engine to keep dieseling when i shut it off.
Is there anyway i could just remove the pully on the alternator and swap it for a larger/smaller one to supply more juice ? If so which gives it more power ? Smaller or larger pulleys ? And no it isnt my belts, all my belts are new the correct part numbers and its fairly tight, nothing is loose