I have a 71 Dart, and if I leave it sit for more than about a week, the battery is to dead to start. I am pretty sure I have a draw because when I connect the negative cable to the post it sparks. Any suggestions on when to start looking? How do I test components?

If you leave your door open or key in the on position while removing/installing battery cable it will spark.. the dome light and ignition system will be active so they will draw current the instant you touch the cable to the battery, hence the spark. But assuming you didn't leave your lights on and door is closed etc, I suppose it could be a sh ort in the wiring somewhere.. feel around the wires and see if any are hot to the touch after the car hasn't been driven for a while. Most likely I am thinking your battery needs replacement. Make sure your alternator/regulator are in order.

I just replaced the battery less than a year ago. I am not sure how old the alternator is. How do I check it?

With the car idiling, put your voltmeter directly across the batery terminals. Should be somehwere between 12.5-13 or so... now rev it and hold it steady... should be above 13, below 14. If it is higher then 14, your regulator might be on the fritz. If voltage doesn't change between idiling and reving, then alternator is suspect

Does it matter any that is keeps the battery charged when I run it every day? It only dies when it sitts too long

Well you need to eliminate one thing after another but assuming the alternator is indeed giving a decent charge, your battery seems that it just can't hold onto it for long and is discharging itself. What kind of battery is it? Exide (and all of its brands) tend to last the least ammount of time especially through harsh weather.

It is an AutoZone battery, I can't find the actual manufacturer on it. I had it through last summer in Arizona.

How much did you pay for it? I would say it is most likely an exide.. thats all the parts stores around here carry.. exide markets their batteries as several different brand names. There are only a hand full or so battery manufacturers out there. And cheap batteries don't like to be baked in Arizona heat...

Try charging your battery with a gentle slow charger then taking it to Autozone to do a load test.. most autoparts stores have a machine that can do that. If it passes, then put it back in the car to see what happens. If it still drains, well, its either the battery or something within the car wiring (At this point I'm assuming you have ruled out the regulator/alternator)

Personally, all the exide batteries I went through never lasted more then a year or two, in any car I put them in. If you do find yourself in the market for a new battery, I would highly recommend an Optima red-top gell cell (available at summitracing if you can't find locally). They can withstand extreme tempratures and have long shelf lives, and can be mounted in any direction. These are a bit more expensive but well worth the investment imho. If you don't want to pay that much, an AC-Delco is a good alternative to exide.

Something else to try... with the key off and door shut and no accessories on etc, unplug both battery cables from the battery, and measure the resistance between both battery cables. It should be a relatively high number. That would be a good way to rule out the internal car wiring

so far every mopar my parents and grandparents owned has done this at one time or another... it'd drain slowly over time if the car sat idle, but charged and ran fine on any daily work/family commute...my grandfather said it was the diodes in the alt that can go bad...replacing the alt cured it everytime.

electrical testing is a methodical and slow process as you isolate and check everything that 'might' cause it until you narrow the field down to a few 'culprits'...

good luck, and be patient.

-D.Idiot

Thanks Pierre, I think I have a lot of things to check. It probably will come down to a combination of the age of the battery and the alternator diodes I am betting. Do you guys know if I could replace the diodes in the alternator without having to buy a new one, or is it even worth the trouble?

Yes you can, I know someone that has rebuilt several alternators by hand and have seen the process. If I recall right there are a total of 6 diodes (2 different types of 3 each) and you have to unsolder then and solder in the new ones. You can also buy bolt on brand new ones for less then $150 (Powermaster brand) and they even come in one wire editions (built in regulator, no more need for original regulator). These are also availible from Summitracing.

Cool, thanks man.

To check the alternator diodes, remove the alternator output wire, then touch it back on the terminal. There should be no spark. If it sparks, you have a bad diode. If you have a high current (10 amp) amp meter then you can put it in series with the output lead and test for current draw. There should be none.

I have also seen the drain problem caused by a small current draw across the top of a dirty battery, so wash the top of the battery as well.

If you have an aftermarket radio with a clock, that will fraw current as well, but I would not expect to see a spark. A spark requires quite a bit of current, which points more toward the diode problem, although I would suspect that a bad diode would drain the battery much faster than yours is doing.

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Chuck Rivers, Webmaster

I'm really betting it is the diodes. I'll probably just replace the alternator.

So, did you fix it?

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Chuck Rivers, Webmaster