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Re: Battery or Alternator - step by step Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 5 Oct 2004 15:06:29
In Reply to: Battery or Alternator - step by step, James Diefenderfer, Tue, 5 Oct 2004 12:06:52 Members do not see ads below this line. - Help Keep This Site Online - Signup |
With the battery charged, turn the key to ON, but don't start the car. Does the BAT light (charge light) come on? If it doesn't, you need to find out why. Power flows from the battery, through the ignition switch, through the bulb in the dash, and finally through the thin wire to the back of the alternator. If that circuit isn't complete, the alternator will not work right. It could be a burned out bulb, or most likely, the wire to the alternator is broken. It's the thin, usually green or yellow wire to the back of the alternator. If you need to replace the bulb (unlikely), make sure you get the exact right bulb - a trip to the dealer is in order. The size of the bulb is critical to proper operation of the charging system.
When you say the car won't start, I'm assuming it doesn't turn over, indicating a battery/low power problem. The alternative is that it turns over fine, just doesn't catch.
OK, so you turn the key to ON, and the BAT light comes on. Get yourself a volt meter. Don't start the car, but turn the headlight switch to parking lights, so they're on. Measure the voltage between the battery posts. Not the clamps, but the actual posts. It should be around 12 volts or so. Now, measure between the positive post and the positive clamp. The voltage between the post and clamp should be less than about 0.05 volts. If it's greater, you need to remove the clamp and clean the mating surfaces, both clamp and post. Heck, do both. The same is true of the negative post. Next, measure from the negative post to the car chassis - no more than about 0.05 volts.
This checks the clamps and wires.
Check the grounding of the alternator. Measure the resistance between the alternator body and chassis. It should be within a ohm of the measurement you get when you touch the meter leads together,. I think the 900 has a grounding cable for the alternator. Make sure it's in good shape, and clean the contacts just for good measure.
OK, start the car. The voltage on the battery should jump up to over 13.0 volts. Preferably around 13.5 or so. Blip the throttle once if it's low. If the voltage doesn't come up, then the problem is in the alternator, most probably the voltage regulator. I'd replace the VR before swapping out the whole alternator.
However, I doubt the alternator has a problem if the BAT light isn't coming on,. The BAT light not coming on tells me either the grounding of the alternator is bad, or the thin wire to the alternator corroded away.
posted by 12.76.129...
, Tue, 5 Oct 2004 15:06:29 <-- Viewing This Message
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