Well, here goes, well the other day my friend sean came over to take me and battery to the local auto store, got it tested, it failed (its 7yrs. old) but brought it back to put back in, and sean hooked up the battery backwards, it sparked a couple times he said and when i ran around the side of my truck, all i saw was smoke coming from near the battery. he said he couldnt see where the smoke was coming from because he was blinded from seeing the sparks (like welding). So i only saw smoke coming from the left side of the battery, and theres only a couple of things that couldve been smoking, the starter solenoid, or the alternator regulator, so i replaced the solenoid and that didnt solve the problem. (all grounds are good and no wires got fried) Any ideas?

 

My guess is that your starter relay is toast. The starter solenoid might be ok as the starter relay wasn't switched. The other option here is if you have a fusable link, it's probably shot as well. Not sure where exactly that'd be, but I'd get out the ohmmeter , and with your battery detached, start checking continuity on the lines in the ignition circuit. I had a battery short out before, and it wiped out the starter relay, the starter solenoid, and most of the wiring around the ignition.

The issue is that the positive potential got sent through the ground, and the starter relay is grounded to the inner fender, so in effect, you took it out of circuit the hard way. That'd be the first place I'd start, as they're cheap. That, and wire....check continuity on the wire....wire is cheap too.

 

Check the fusible link. It's connected to the battery side of the starter solenoid. A quick check is to take the fusible link and "tug" on the wire. If it feels "soft" or "gives" when you tug, the link is bad.
There is also a real good chance that the diodes in the alternator got fried and possibly the voltage regulator.

 

When you hook up the battery backwards, you reverse-bias the rectifier diodes in the alternator. This makes a dead short, which pops the fusible links. You've either fried the fusible links, the alternator, or both (most likely both).

 

Well I had my other friend devin come over, and we got a new solenoid, put that on, and just like you guys described, the fusable link melted and pull right apart, so we soldered in a fused wire instead and now she starts! Thanks guys!!!

 

I know this is an old thread, but I figured I'd give this a try. I also hooked a battery up backwards by trying a different battery and not taking the time to notice the terminals were backwards from the one I took out. Stupid mistake I know, but it is what it is. Since then the starter, alternator, starter solenoid, and the battery have been replaced and the truck cranks and runs fine. The problem I'm having is there is a constant drain on the battery coming from somewhere that I can't figure out and it don't seem the battery is charging like it should when the truck is running. The alternator is working as it should because once running you can unhook the battery and the truck still runs fine, but if you leave the battery hooked up all the time it will eventually go dead and leave you stranded. It's at a shop right now having the wiring checked out, but once I saw this thread I figured I'd see if anyone else has run into this. Thanks for any insight in advance!

 

How long does the battery take to drain? Overnight or days/weeks?

 

You mentioned a replacement alternator, but keep in mind it wouldn't be unusual to get a defective alternator right out of a new box. One standard diagnostic when testing an automotive charging system is to check for "AC Ripple", remember while this is a DC charging system, there will always be some, even if very slight. I think this indicates defective diode or diodes if excessive. There are 6 diodes in an alternator. If even one is marginal it will cause trouble. See if you can find a local shop that has a good battery & charging system tester. SnapOn makes one, I'm sure there are others. They'll usually test for free, they want to sell you the parts.

As a practical matter put your hand on the case of the alternator in cooler weather after it has sat a while. It will feel warm if a diode is bad.

 

It's hard to tell really because the truck isn't a daily driver. I read somewhere to check if you have a drain on the battery when the switch is off to take the negative cable off the battery, hook a test light to the terminal and touch the end of the cable; if the light comes on there is something pulling current even when the switch is off and it does that. The time it put my dad down it sat for probably a week with a brand new battery and he said when he started the truck it cranked slow, but it started so he drove to where he was going. When he came out to leave the truck wouldn't even turn over and he had to get a jump. I feel like if the battery was getting charged like it should when he drove it probably 15 minutes to his destination it should have charged enough to start when he was leaving. I could be wrong, but it's just the way I was thinking.

 

The starter, alternator, and solenoid were all done at the same time by the mechanic that rebuilt the engine. He did have problems with a couple alternators not putting out what they should, but when he tested the one on it now he said it was putting out like it should. I don't know what it was putting out because I won't there so that's about as much as I know about that.

If we keep the battery disconnected the truck will start like it should every time so it could just be the slow drain on it as long as it sits between times it's driven.

 

An alternator can both charge the battery OK and still be defective at the same time. It's not an either/or thing. Automotive start Batteries don't really like to be drawn down hard on a repeat basis, it will ruin them fairly quickly. It also stresses the alternator innards trying to charge them back up all the time.

It's kind of "interesting" from a technical standpoint how a single tiny fault somewhere in the charging system, if left unchecked, can sort of snowball over time into some seriously expensive Unpleasantness.

 

I've only let the new battery get drained once and I used a charger overnight to get it charged back up. Since then we have kept it disconnected when the truck is just sitting.

 

I just can't figure out how anyone could hook it up backwards when the battery post are clearly two different sizes ? It just wouldn't work because one is bigger than the other.

 

Different battery configurations, some have the posts reversed from "normal".

The terminals don't need to be connected, just momentary contact is enough to do damage. The instant fireworks display is usually enough to persuade people to stop right there, but I'm sure some are more determined than others.

I'm surprised the SAE didn't decide on making one terminal a square or triangle or something though.

 

You're surprised someone can make an honest but absent minded mistake? Must be nice to be perfect all the time.

The negative cable terminal easily slips onto the positive terminal. Then, all it takes is slight contact with the positive cable to the negative terminal and zap goes the fusible link. Seems very easy to "figure out" how someone could do this.