I have an 84 Blazer and it runs great. I have a problem with the battery going dead. I can charge the battery (new battery) and start it and it starts great. If I don't take the cables off when I let it sit (just over night) it won't start the next day. Where could the battery be being discharged? Any suggestions are appreciated. Rodney

 

you have something staying on. check and make sure the lights are off, and nothing else is left on.

 

One thing to check and see if something is actually being left on is to put a test light in series with one of the battery cables. Remove one of the terminals (doesn't matter which) and put a test light (12v bulb with socket & wire leads will surffice) and touch one lead to the battery post and the other lead on the battery cable. So if you use the negative terminal, one lead would be to the negative terminal on the battery and the other would be to the negative battery cable. If the light lights up, you know that you either have an accessory being left on, or you have a short somewhere in the system. The next step is to start pulling fuses to different areas. If you pull a fuse and the light goes out, then your problem is on that circuit. If you end up pulling all of the fuses for the interior, then you may have to check on electrical connections/accessories under the hood.

I have seen alternators short internally and not cause any other problems besides draining the battery.

 

Are you sure its getting recharged while the engine is running?
The battery provides power while the engine is off, once the engine is running the alternator provides power, unless the alternator cannot provide enough power then the battery supplies it instead. Draining the battery. With me so far? Should be a wire running from a stud on the back of the alternator to the battery. Make sure it is good, dissconnect it and look at it. One strand will make your ohm meter read it as good, however that one strand isn't enough to charge your battery. The other wire runs to the cab of your truck, should be a fuseable link within 12" of the alternator end. Find it and make sure its good. Is it burnt, crsipy, swollen unevenly? After you check both wires out, move them out of the way of the fan and belt, and start the engine. Did your bat idiot light come on? Do you have a voltage gauge? What does it show? Have you had your battery and alternator tested? Find a local service center that does free testing. We can test it while both are in the vehicle. Try the local autoparts stores, maybe they can test it in the truck as well.

All vehicles will draw power with the engine off. Your radio needs juice to run the clock, it doesn't magically know what time it is when you start the truck up the next day. Plus most aftermarket alarm systems draw power with the engine off. I also think the PCM draws some power as well. The only way I know how to make the test light effective is to start pulling fuses. Start with the raido, alarm, and pcm. If the test light goes out, good. If not, time to start pulling fueses and see which one turns the light off. Once you get them all out, plug that one back in. Does it still make the test light come on? That is your trouble circuit.