Need Help, electrical problem with my car, Key off,power runs from battery

[sam sarrha]

thru the wire that leads to the bolt on post on the alternator. I have replaced several alternators.. that have tested "Bad Diodes". the alternator will pass a 'engine running' test but when i remove the alternator it fails the bench test with bad diodes.

the battery is drained dead if i let it set. this ruined a good 750 amp battery. i had them test the one alternator off the shelf and it failed.. I have a lifetime replacement alternator.

is it normal for 12volts to drain from the neg post to the cable with key off..?? i have removed every fuse and unclipped every connection under the hood.. when i pull the white wire from the Pos cable that goes to the post with the nut on the alternator it flows 12 volts. i have heard that is normal.. but at low amps.

i am not working due to an injury and cant afford to take an "Electrical" problem to a shop.. this is the 3rd alternater..not counting the one off the shelf that failed the bench test.. i just bought a new battery and have been just disconnecting the neg cable when i stop..

thanks for any help..

[sam sarrha]

1. I dont have an Amp meter, but i used a small running lite bulb with the

flat bottom and the contacts as wire lupes on each side.. i made contact with the post and cable and the filament only glowed red for about 1/8th inch...

[nedbal]

3. OK I should have concentrated on this part

>>>I don't have an Amp meter, but i used a small running lite bulb

that good, it sounds like you disconnected the post and cable and put your test lamp in series ?


>>>the filament only glowed red for about 1/8th inch.

was this a 12 volt test lamp such as from a turn signal?
if so it sounds like it's glowing too much
pull the fuses one at a time, see if the glowing goes away.
if you find one where the glowing stops, make a note of it and put it back in. Do this with all the fuses.

if you're using a 12 volt test lamp for this and the glowing is hard to see, use a 3 volt flashlight bulb and it should be easier to spot.

the radio and computer should not draw that much current (amps) when off for a 12 or 3 volt lamp to glow.

Some cars have air suspension or other items (cooling fans) that will draw current when the car is off, but only for a minuet or two

good luck

[nedbal]

2. We need to define what you're doing

>>>>"Need Help, electrical problem with my car, Key off,power runs from battery"


yes a trickle of mili AMPS will flow to the computer and radio and such


>>>thru the wire that leads to the bolt on post on the alternator. I have replaced several alternators


yes see above


>>>>that have tested "Bad Diodes". the alternator will pass a 'engine running' test but when i remove the alternator it fails the bench test with bad diodes.


So you know how to do a bench test of the 3 diodes out of circuit with a ohm meter??


>>>>> i had them test the one alternator off the shelf and it failed.. I have a lifetime replacement alternator.


so the store did these tests? and right off the shelf it failed ?


>>> is it normal for 12volts to drain from the neg post to the cable with key off..??


uh... neg post is the cars are ground they
are equal to each other. the cable (red ? / positive) yes a very small amount will drain over time. A fully charged battery should hold for a month and still start under normal computer and radio drain conditions.



>>>>this is the 3rd alternater..not counting the one off the shelf that failed the bench test


I have had newly rebuilt alternators not put out their full spec output. once I had to try 2 and the 3rd one worked to full spec