Battery won't hold charge

The battery in my car dies if you leave it set over 2 days. If I start my car every day, it works fine. When I get out @ night, I turn everything off. It has a new battery & a new alternator and I checked the fuse box & the fuse for the rear defogger was all melted, so I cut the wires loose & taped them off and may put an in-line fuse in it, but it still drains the battery after setting for a day.

I?ve checked the grounds & looked for broken wires, checked a lot of the plugs & none are hot that I can find. I think there must be a bare wire someplace, but I can?t find it.

Even though it?s an old car (a 1994 with 120,000 miles), it runs fine otherwise & I use it for a work car, so I need to keep it dependable. Any suggestions on what else I can check that might be draining my battery?

If you remove the cable from one of the terminals, does the battery still drain? If so, you have a defective battery. If not, you have a short somewhere. You can get a circuit tester, take the negative terminal off the battery, and clip the circuit tester to the battery and the cable. The tester will light up when current is flowing. Start pulling fuses until the light goes out.

The melted wires might be a red herring but they concern me that you have a short somewhere, if you melted the fuse you may have melted other wires. Although I am quite confused about your description that you “cut the wires.”

No, it doesn’t drain if you remove the cable. By “cut the wires,” I mean I cut the two wires out of the back of the fuse box going to the rear defog because it melted the fuse and the whole area. You can’t even put another fuse in. I was going to put an in-line fuse in. But I want to find the problem first.

I agree with StrongDreams, except for If not, you have a short somewhere. It is not likely a short, but rather a power drain. Use a amp meter to determine what is drawing unusually high current after your shut off the car. Note: the drain will vary. The higher drain may not be there when you first turn off the power, but may show up a few minutes or hours later.

It is also possible the replacement battery was bad to start with. Don’t assume that because you replaced it the new one is good.

You can have the battery load tested, but it sounds like the battery itself is OK. You have some serious electrical issues with “melting” fuses etc.

If you have a multimetter you should be able to see the drain on the battery when the car is “off”. Then remove one fuse at a time and see if the draw in the meter changes. Perhaps you can identify the circut(s) where the power is draining. Obviously the one that melted the fuse means some melted wires and connectors are likely too. That’s the circut to suspect first.

One approach is to pull different fuses each night until you find the one that makes the problem go away. Then you can start looking at the equipment on that circuit for a malfunction.

Not that it matters, but I’m having trouble understanding what cutting the wires did that leaving the fuse out wouldn’t have done.

Nitpicker. He either has a short, or a defective piece of electrical equipment that is draining power when it should not. I’m leaning toward a short somewhere in the rear defogger system that is upstream of the fuse. If the fuse is so badly melted that he felt he had to cut the wires off the panel to stop the flow of juice, I’d wager there are other melted wires in that circuit, and if they are between the battery and the fuse, that could still be the problem.

Thanks for all your suggestions.

My windshield wipers have stopped working now. I hooked the wires back up (that I cut) and that didn?t make the wipers work. I haven?t put an in-line fuse in yet to see if it keeps blowing it because I haven?t had the time.

Don?t know if this is relevant, but the two wires going to the rear defog fuse (that I cut) ? one is hot all the time & when you turn the car on, they?re both hot. I don?t know where to start tracing the wires for the rear defogger (floorboard, backseat, roof?). Don?t have a schematic, but I?m going to try to do that this weekend.

I checked the fuse box on both the drivers? side & the passenger side & the maxi fuses under the hood & there?s no other blown except for that rear defog

I?m going to try to try what StrongDreams suggested (with the circuit tester) hopefully tonight, but maybe this weekend.

I might be slow to respond because I?m working on the car after work hours & in my spare time, but if you have any other suggestions, please respond. I?ll be checking in.

I think two or three problems. The defogger does draw a lot of current when it is on, but the fuse and wiring should be sized to handle its normal current draw. So probably its hot side is shorted to ground somewhere. That’s going to be difficult to isolate except by looking for singed/melted/burned components because the normal resistance to ground across the heating element isn’t very high so your ohmmeter is going to show pretty much zero everywhere in the circuit.

As far as the current drain to the battery, I think you probably need to conjure up a rig that will allow you to pull the fuses one by one and measure the current flow across the switch terminals with the ignition switch off. You should find a small current flow to the radio and another to the car computer. I’m not sure how much, but I’d guess a few tens of milliamperes for each. Presumably, you will find a much larger current that shouldn’t be flowing going through one of the other fuses.

Wipers? Normally, I’d guess the switch or wiper motor. But since you’ve been futzing around with the fuse block, I’d also check to make sure that you haven’t knocked a wire loose there or inadvertently partially unplugged the wiper fuse.

I think I’d drop by the parts store and see if they have a Haynes or Chilton manual with wiring diagrams. You are very likely going to know more about your car’s wiring than you ever wanted to by the time you have all this sorted out.