i can't seem to figure out whats wrong with my charging system on my S13 SR20. the battery tested out good and i just pulled the alternator off and had it tested and it tested good. but for some reason my battery won't stay charged and the battery light on the dash stays on while the car is running. when i hook the battery up to another car the light goes off. but as soon as i pull the jumper cables off the light comes on again... any suggestions

 

check the voltage on your alternator charge wire (I think its the white with blue stripe on the back of the alt) and make sure the charge is coming off of it, and if not check the plug that plugs into your alt cause it may have bad contacts.

 

ok, i checked the charge wire and there is a charge comming off the alternator. right around 15v while the car was running. i even disconected the plug off the alternator and its reading around 12V. it doesn't make sense to me it looks like the system is working correctly but for some reason within like 5 min. of running the engine the battery drops to almost 8v. i can't figure out what is draining my battery while the engine is running.

 

switch out the battery, and try it a few times. I know this sounds stupid, but it just happened to an RB20 car I had at the shop, I tested the whole harness trying to find a short, and it turned out to be a shorted cell in the battery. threw in a new battery, and it worked like a charm.

 

well i switched out the battery and still no luck. ...

 

replace your battery cables and make sure you have very good grounds. wire brush them before you bolt them down. This is most times a case of a bad ground wire, but you might as well replace both while you are at it. Start with the ground though, thats most likely the one causeing the problem.