94 jimmy idles fast, battery light on

[toolmaker3]

i ahve a 94 S15 jimmy with around 135000 miles on it. Today it would'nt start back up after I had just drove it to pick the kids up. Got a jump and took it back to the house. On the way home I noticed the battery light was on. So I went ahead and bought a new battery and replaced it( other one was over 5yrs old). So new battery in and guess what. It will crank over and start but barely. And when it does the engine idles way to fast. Also the battery indicator light is still on. Decided to take it for a short drive around the block and it idles so fast that it would accelerate up to 50 and that's when I started braking to keep it from going any further. I have tried to start it a couple of more times and the same things happen. Where should I look at next? this is just started.

Thanks

[taillight]

Sounds like the alternator is also bad. Charge the battery and then test the alternator.

[old_master]

Battery voltage is applied to one terminal of the battery indicator bulb when the key is in the RUN position. The other terminal of the bulb goes to the voltage regulator, which is inside the alternator, (brown wire). When voltage goes through the bulb to the regulator, the regulator excites the field in the alternator, and the stator starts to produce voltage. When the regulator senses voltage output from the stator, it removes the ground for the indicator bulb and the light goes off. When the battery indicator light is on, the stator is not producing voltage to charge the battery. If the fuse for the indicator light is open, the battery indicator light will not come on when the key is turned to the RUN position, and the alternator will not charge the battery. The indicator system is quite simple, but yet misleading. If the light doesn't come on when it should, or comes on when it shouldn't, there's a problem. Think of that light as an "alternator" light, not a battery light.

[toolmaker3]

Thanks, for the tips, It ended up being the alternator. I took the old one off and had it checked and it was bad. Replaced with a new one and everthing is fine. I guess what threw me off was the idle speed but thinking about it know if its not getting the correct voltage then that would cause it to go out of whack.

thanks again.