How To Determine If Battery Is Leaking Through Alternator

[PatrickDaBronc]

Leaving battery posts on drains battery overnight on my '89 Bronco2... it'll run all day if I remember to take a terminal off and reconnect it in the morning. If I forget, a jump in the morning works immediately. I'm assuming the alternator is leaking current; how do I check before replacing the alternator?

Thanks in advance...

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[AdamDude04]

Sounds like an accessory of some sort is on (radio, lights (burnt), something).

Highly doubt it's the alt..I don't see how it can leak electricity. Something needs to be using the power

 

[Bronc76]

You could drive to the local auto part store to have alt tested.

 

[colby72olds]

Mine does the same thing. I figured it is my alternator because the bronco dies as soon as I disconnect the terminal. Like you, I have no problems during the day though so it has me confused a little.

 

[Bronco Chief]

I'm working through the same problem right now on my 91 Bronco. Every morning the battery was dead. Had the charging system tested at two different places and they both said the alternator was bad. I replaced the alternator but the drain was still there. I hooked up an ammeter to the battery which showed a 3A drain with ignition off. No wonder the battery was dead! After an internet search I found an article which said a high drain like that was probably coming off of the starter relay. I pulled each of the wires off of the starter relay and found one which was showing it was grounded. It looks like the wire which is the problem goes to the alternator. Moving the wires around has stopped the drain so it looks like it might be an intermittent short. I'm going to replace the wire and hopefully the problem is fixed.

 

[50joe]

Easiest way to check for a draw:

Pull the Neg. battery cable, and connect a test light between the post and the terminal. If there is a draw, the light will light. Leave it on, and start at the fuse box. pull the fuse for the interior lights, since the door has to be open, or you'll be at this all day. Then one by one, pull each fuse untill the light goes out. When you find the fuse that shuts off the light, thats the circuit to check. If none of the fuses shut off the draw, then you can start disconnecting the alternator, regulator, and or starter solenoid untill you find the draw.

 

[PatrickDaBronc]

Easiest way to check for a draw:

Pull the Neg. battery cable, and connect a test light between the post and the terminal. If there is a draw, the light will light. Leave it on, and start at the fuse box. pull the fuse for the interior lights, since the door has to be open, or you'll be at this all day. Then one by one, pull each fuse untill the light goes out. When you find the fuse that shuts off the light, thats the circuit to check. If none of the fuses shut off the draw, then you can start disconnecting the alternator, regulator, and or starter solenoid untill you find the draw.

 

[miesk5]

yo, good info;

Parasitic Current Drain Testing Methods

Source: by bbbind.com http://www.bbbind.com/Bulletins_Attachment/Parasitic%20battery%20draw.pdf

Troubleshooting with a Test Light (low resistance); "...low resistance test light can sometimes be used in place of a blown fuse. The light will illuminate while a short circuit to ground exists. DO NOT use a medium or high resistance test light in place of a blown fuse. These types of test lights illuminate with very small amounts of current and can be misleading..." read more

Source: by ocw.weber.edu @ http://ocw.weber.edu/automotive-technology/ausv-1320-automotive-electronics/10-trouble-shooting/short-circuit-detection

or;

Troubleshooting with a Test Light (low resistance)

Source: by Chris B at http://blog.rv.net/2008/10/tech-troubleshooting-with-a-test-light/

Voltage; "...a normal battery that is fully charged produces 12.6 volts, not just 12.0 V. (Remember, when measuring battery voltage, everything in the car should be off, or the battery should be disconnected. Voltage measurements are always "no load" measurements unless the battery is being tested for it's performance under load)..."

Source: by Gordon

also, look up OptimaJim; he just registered and posted here.