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johnmyster · 08-21-2008, 10:48 AM

On my '98, there's a diode in the underhood fuse box. It's disguised like a fuse, but it's really a diode. I pulled it. No more DRL. The autozone.com wiring diagrams aren't good for everything, but they DO have really complete schematics for lighting. It may show you that there's a fuse, relay, or diode somewhere to pull or otherwise disconnect on yours.

Could try also an underdrive pulley on the crank. Slowing down the accessories by 25% couldn't hurt. They're generally $70 or so and you'd need a belt 3" shorter. Pretty common amongst the 4-cyl S10 guys. I'm also installing the smaller alternator pulley in order to keep it at full speed, though I rarely drive with AC, and rarely at night, so I could probably do without it. Thus, any gains I have will be related to slowing down the PS pump, AC, and water pump. At 3000 rpm at 70mph, I don't think they'll miss it. If I have good voltage with my efans, I'll probably go back to the stock alternator pulley.

I'm not a fan of the disconnected alternator deal. However, know that you can fit a group 78 battery in your truck by using a pair if channel-locks to tweak the inside edge of the battery tray. The 78 battery is about 1.25 inches longer than a group 75, but our trucks have about 1.2 spare inches to begin with. I did it in the parking lot of the store when I got my new battery last weekend. Alternator or no alternator, a bigger, higher capacity battery (for the same price) is just a better deal.

If I could get rid of these 235 width tires on mine, we could probably do a bit better...

Not to start a fire on here, but I think that the 10% gain reported by MetroMPG seems a bit lofty. I know my engine is tiny, but there's no way 10 percent of its power is going into the alt. If his alternator and belt drive is only 80% efficient, one horsepower is still 43 amps at 13.8 volts. I'd say my charging, ignition, ECMish, and lighting loads are probably in that ballpark. One horsepower.

On our trucks, you won't be able to kill the belt to the alt. However, the AZ wiring diagrams will show you that there is an external feed that energizes the coil. On mine, the ECM activates the alt. On yours, perhaps, perhaps not. However, you could put a relay in this line, and, for instance, run the alternator only with the brake lights, or only after starting, or manually with a switch when the lady demands AC.

08-21-2008, 10:48 AM	#2 (permalink)
johnmyster EcoModding Lurker Join Date: Aug 2008 Location: Virginia Posts: 87 Brown Bus - '98 GMC Sonoma X-Cab SLS 90 day: 31.37 mpg (US) Thanks: 0 Thanked 2 Times in 2 Posts	On my '98, there's a diode in the underhood fuse box. It's disguised like a fuse, but it's really a diode. I pulled it. No more DRL. The autozone.com wiring diagrams aren't good for everything, but they DO have really complete schematics for lighting. It may show you that there's a fuse, relay, or diode somewhere to pull or otherwise disconnect on yours. Could try also an underdrive pulley on the crank. Slowing down the accessories by 25% couldn't hurt. They're generally $70 or so and you'd need a belt 3" shorter. Pretty common amongst the 4-cyl S10 guys. I'm also installing the smaller alternator pulley in order to keep it at full speed, though I rarely drive with AC, and rarely at night, so I could probably do without it. Thus, any gains I have will be related to slowing down the PS pump, AC, and water pump. At 3000 rpm at 70mph, I don't think they'll miss it. If I have good voltage with my efans, I'll probably go back to the stock alternator pulley. I'm not a fan of the disconnected alternator deal. However, know that you can fit a group 78 battery in your truck by using a pair if channel-locks to tweak the inside edge of the battery tray. The 78 battery is about 1.25 inches longer than a group 75, but our trucks have about 1.2 spare inches to begin with. I did it in the parking lot of the store when I got my new battery last weekend. Alternator or no alternator, a bigger, higher capacity battery (for the same price) is just a better deal. If I could get rid of these 235 width tires on mine, we could probably do a bit better... Not to start a fire on here, but I think that the 10% gain reported by MetroMPG seems a bit lofty. I know my engine is tiny, but there's no way 10 percent of its power is going into the alt. If his alternator and belt drive is only 80% efficient, one horsepower is still 43 amps at 13.8 volts. I'd say my charging, ignition, ECMish, and lighting loads are probably in that ballpark. One horsepower. On our trucks, you won't be able to kill the belt to the alt. However, the AZ wiring diagrams will show you that there is an external feed that energizes the coil. On mine, the ECM activates the alt. On yours, perhaps, perhaps not. However, you could put a relay in this line, and, for instance, run the alternator only with the brake lights, or only after starting, or manually with a switch when the lady demands AC. __________________ Meh Truck Last edited by johnmyster; 08-21-2008 at 11:06 AM..