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Re: charging light light stays on Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Sat, 14 Feb 2009 18:18:43 In Reply to: charging light light stays on, michael erhardt, Sat, 14 Feb 2009 06:05:48 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If the Battery light is on, the alternator isn't charging the battery. The battery shouldn't discharge overnight. However, if the new battery didn't get charged properly, it can discharge.
Step 1 is to get things charging right. Then you can look for discharge paths, if there is one.
You changed the alternator - I assume the new one came with a new VR. If not, a new VR is a really good start.
Before doing anything, do a visual inspection. There is a thin wire that goes to the D+ post on the alternator - that wire comes from the battery light. Make sure the wire is connected to the post, and not grounded. Make sure the wire doesn't have a worn spot and is touching ground. Make sure the alternator belts are on. Make sure the ground strap from the alternator to the engine is in place.
With a charged battery, turn the key to ON - the battery light should come on. Turn the key off, and then disconnect the thin wire from the D+ post and let it float free - don't let the bare end touch ground. Turn the key to ON - the battery light should be off. If it doesn't go off, there is a short to ground on that line.
Assume the light goes out when disconnected - re-connect it. Next, you'll need a voltmeter. Even a cheap one will do. Measure the voltage on the battery, engine off. It'll be around 12. 5 volts or so. Start the car. The voltage should jump up to 13.0 or higher (when measured against ground). If it doesn't measure between the alternator body and the engine - it should be less than 0.1 volts - if it is more than 0.1 volts, the alternator ground is bad. Next, measure between the D+ post on the back of the alternator and ground, It should be up around 13 volts. If it only a couple of volts, try reving the engine. If the voltage doesn't jump up, then I'd suspect the alternator.
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