I noticed that after my engine swap that if the car sits for a day or two, the battery will die. If I boost it, it will start right up. I didn't have this problem b4 the swap, so I'm pretty sure I did something. I put a test light between the neg. cable and neg. terminal, and the light lights up for a second, and then goes dim to nothing. I even put an ammeter between the two but didn't register any current. The only thing I can think of at this point is maybe the starter solenoid maybe be wired backwards? I wasn't sure which wire went on each terminal so I bolted it up and it worked, so I figured I was good.

What else should I look for?

Thanks

Try disconnecting your alternator and seeing if it still discharges. I know if the diodes go bad they will short and drain the battery. I learned this first hand, with an alternator that appeared to charge fine when running, but after a couple days of sitting, the battery was to low to start the engine. With a new alternator the problem went away!

check for loose connections.
this same thing happened to me about 4-5 years ago. my negative cable that connects to the block was bad. the lug had cracked and you could see where it had gotten hot. i replaced the cable and no problem. also check the connections by the horn relay (behind the drivers headlights as well as the little terminal behind the passengers headlights. both of these parts on my car were so old they basically crumbled when i touched them.

as you can tell, i went through my entire electrical system 4-5 years ago. after some easy parts replacement and some resoldering and re-lugging..... no problems.

Is 6 milliamps too much draw? I put my meter on there again ands that what I came up with.

how did you measure this?
** clamp-on type meter?
** VOM (like a fluke) that you put in series with the positive lead?

also... did you have the meter set for DC?
6 milliamps is quite small (0.006 amps). i would think this small draw wouldn't kill the battery overnight.

Oscar,

I put a Fluke in series w/the negative, and yes set for DC.

It might actually take 2 nights to kill the battery.

If you have elimnated the alternator as the source of your short, try removing fuses one at a time from the fusebox until the short doesn't show. At least this will eliminate those circuits as the source and narrow it down. Same with other circuits you think maybe have the short, like the wiring to the starter solinoid etc...

Maybe it's just a coincidence, the engine swap and the battery going dead. You could just have a weak battery. Just disconnect for a few days and see if it will start. Batteries can get internal shorts between the plates, small shorts, that take days to drain the battery. As long as you use them everyday they're fine.

sounds like you measured it correctly.
maybe the battery is bad as mentioned above.
i would still go through and check all the connections. also check things like the switch in the glove box.... might be on even if the door is closed.

Thanks guys I will try your suggestions.

Have you checked the voltage at the battery while its running then right again after you shut it off? Should be charging at around 14.5 volts and shouldn't drop much when you turn it off. You could check all the connections as suggested, that can keep it from charging fully, also cause lights to be dim, turn indicators to not work, lots of weird symptoms. A bad connection shouldn't cause it drain though.

a loose connection will cause an increased drain. when my negative cable lug was broken, the current flow caused an arc to form which was like a small welder. it heated the lug and you could see where it got really hot and melted the metal of the lug. this "welding" would drain my battery in a day or so. when i replaced the cable, the battery never drained again.

don't ya just hate this kind-a stuff!
i would rather have something "fail-bigtime" to tell me that "hey... i'm the problem" instead of these goofy here today, gone tomorrow, here the next day problems.

hope you find it.

yup finding the problem is always the hard part, fixing is easy once you know whats wrong. this 'kind-a stuff' is what you're in for when talking about 34 yr old cars. but they're worth it.

Guys (Hello Again Finally)

I am killing myself with this on my daily driver. I have an older Honda Accord with 110K miles and it runs perfectly. If I let it sit for 3 or more days..... poof dead battery! I have identified 3 fused circuits in the car that have diminutive current draw whan the car is shut off. They are drawing in the area off milliamps (can't recall the number but it is single digit) as tested on my Fluke multi meter so I doubt that such a small draw is the culprit.

It charges at 14.3 volts running and the battery is new (matter of fact they warranteed a two week old battery that died while I was outta town) so that is not the issue. When the battery discharges it goes dead D-E-A-D. DEAD. I mean it is soooooooo discharged I have to put the charger on "Start" to get the battery voltage high enough that the auto monitor in the charger recognnizes the battery as needing a charge.

What is this about the Diodes?. I know a diode is a one way electrical "Valve" and it should only allow current to flow in one directon only. Are we saying that the diodes being bad can allow the alternator to actually draw current? In effect the alternator is trying to behave like a motor and take current from the battery?

How does one check for this. I can see the potential...no pun intended....for the thing to just sit there and convert the voltage to heat. The alternator trying to run like a motor (assuming I am right in that conclusion) cannot hope to turn the engine over so what ya get is heat until the battery croaks. How would ya go about testing this????

Also I recall at times my battery charge idiot light would just sorta temporary flash on then right off again. Never figured it out and it was a long time ago but given electrical problems now I wonder if that light going on and off was possibly a harbringer of the current ( again no pun) problems.

Diode testing is the key here...I think. Any help as to how this can be diagnosed / isolated even if based on Chevelle experience would be great

Here is some info from a site another member posted a while back,

The alternator is a three-phase generator with a built-in rectifier circuit consisting of six diodes in a full-wave bridge rectifier circuit. The DC voltage and current from the battery is supplied to the Rotor through the use of slip rings mounted on the pulley shaft.
In essence the diodes are solid-state switches with no moving parts, making them maintenance-free, until a failure mode is encountered.

When they fail, they usually short, either totally or partially. Partial shorts in diodes are referred to as “leaks”. Leaking diodes will allow charging of the battery, and when the vehicle is left sitting for a period of time, like overnight, the battery may discharge through the leaky diodes and not start in the morning.

Here is a link to the site, lots of good info.
http://207.158.221.52/gw/alt/Alternator_Theory.html

oman, if you have a shorted diode you should, I believe be able see that by switching your meter to ac instead of dc and see what kind of reading you get. like wayner said the diodes form a full wave bridge rectifier to convert an ac source, alternator, into dc. a shorted diode will allow ac to pass through. i now this works in other cases but the battery is like a big capacitor and tends to smooth out the ac so it may not work. of course another option is to take it to your local auto parts store and have them check it.

Finally

Where do I put the meter when I have it set to AC? Same place I had it when I had it set to DC and tried to identify circuits that were drawing current? I had the meter in series between a battery pole (the positive one) and the the positive battery cable.

The engine is not running when I do this I assume. I suspect it should NOT be running ...we are trying to identify a fault that may exist when the alternator is not being driven by the engine so I am assuming I do this A/C setting on the meter test with the engine not running.

As for the local parts store. Not much chance of that happening. It is staffed by the same people we were discussing the other day. If I can't figure this out with a little help then to hell with it. I am NOT getting involved with the parts store guys. I could launc into another discussion about that situation with equal vigor as I entered the "Why Johnnie can't spell" discussion. Down here in Atlanta most of the parts store guys are not even legal from what I can tell.

Gonna read the suggested topics highlighted above and look at my Chiltons "One fits all" Honda Manual. It covers all the Honda models of that time frame and while helpfull it always seems to talk about the topic I want to understand for my 89 in terms of an 90 or 91 or in terms of a Civic rather than an Accord.

Stay tuned.

You want it across the the battery but want the car running. If you have a blown diode you'll only be able to read ac current when the alternator is turning. Again, I'm not positive this works in a that type or circuit, particularly since it's a 3 phase, 1 out or 6 diodes might not show up. It does in a dc power supply, like electronics, that's 1 out of 4, 25%. Did you check out that link from wayner. There may be a way to measure the resistance with the alternator disconnected, I'm not sure. If it's easily removed I'd go with taking it to a rebuild shop or auto parts place and let them tell you. Guess I've been lucky, everytime i lost an alternator it just quit. Good luck!

Yes the most common problem with alternators is spent brushes, then they just stop charging.

I do not know how to test the diodes, for just leaks. Certainly isolating the alternator alltogether from the car by totally disconnecting it, and seeing if the discharge and low battery level is still happenning.

Sorry if this post seems hyjacked!

Originally posted by wayner:
Sorry if this post seems hyjacked! Agreed. For both problems the quickest solution is take it to the auto parts place and let them check it. They can tell you in 10 minutes what you'll fart around with for days. They can test the battery and charging system with everything hooked up. Not sure if you have to pull the alternator to run a more thorough test to find a leaky diode.