2000 GMC Safari. About 2 weeks ago, I noticed the current guage was a bit lower than normal, then after a long drive with a/c on, did not want to start again. I bought a new battery and noticed that the terminals were dirty with white acid poweder, so I cleanned them up and installed the new battery anyway because I was in a public parking lot and it was a hassle to get people to wait for it to charge enough to start it up. It ran fine and the guage seemed to be ok, very close to 14v. I still thought that the alternator was the problem, but then I asked a mechanic, he said that if the guage was reading 13+ v, that meant that the alternator was doing its job, that it was probably the dirty cables. a couple of days later I drained the battery due a minor current draw from a bazooka speaker that I forgot on, then I jumpstarted it. Now my question is, if the battery gets drained totally, does it get damaged? Now everytime I turn the A/C on, the current drops a lot, almost in the red area, like 10v but if I turn the AC off, it goes back to normal, the if I rev it up, it goes up to almost 14v, is this normal? WOuld I need a new alternator? THanks a lot.
Charge the battery with a battery charger, slow under 20 amps is best, under
10 amps even better. If you ran it dead dead, the alt is never going to put a full charge on it . One discharge should not kill a quality battery, repeated discharges are another story. Make sure you got the terminal ends clean, you have to pull the bolts out of them to do a proper job. With a small pocket screw driver you can walk the "rubber" covering off the terminals like taking a bicycle tire off a rim. Clean them good, and walk the covers back on the same way. As amperage draw increases, voltage drops, the battery is pulling big amps because its in a discharged state. Turn the AC on and its another 20-30 amp pull on top of the fuel pump, fuel injectors, sensors, the computer etc etc . Running it in a discharged state will damage the battery.
WL is mostly right. I just feel compelled to correct a minor point. If the terminals are dirty the resistance will increase. This will cause the voltage to decrease. This is the reason for the increased current. (Ohm's Law) Chevy battery terminals use the bolt in style. So when the mating surfaces get dirty more current goes thru the bolt. This is bad. Keep the terminals clean. Mike
You have corrosion on the positive battery cable/terminal connection. Take the positive terminal off. It has 2 cables attached. One of the cables feeds the starter, the other feeds everything else. Split the rubber boot and separate the terminals and spacer washer. There will likely be a lot of corrosion here. Wire brush everything good and soak in baking soda solution, then wire brush it again. Once you have bright metal, reassemble the terminals, washer, and bolt. Now there are two schools of thought here for what to do next. One says to coat the terminals with vaseline to inhibit corrosion. The other says to coat the terminals with an insulating rubber compound that you can brush on. I have used the vaseline solution with great success. Be carefull around the battery after this, as there is an exposed 12 volt source.
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