Battery discharging...can't keep it charged ('75 Scout II)

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brosamj

New member
I have been having a problem with my '75 Scout II. It drives great, but if it ends up sitting for a few days in colder weather (not too cold, mid 30s - 40s), the new battery gets completely drained. I have replaced the alternator. My mechanic shop tests the alternator and it is charging the battery fine. If I just start the Scout II but don't drive it around and let it sit for a few days without driving it, it just won't start up. If I drive it pretty much every day, no problems.

I had the ignition switch replaced as well to see if that would fix it. Any thoughts on what is draining the battery or causing these problems?
 
The most common cause of this issue is an alternator that has a partially-failed rectifier assembly. This will not show up normally in a typical test conducted on a machine at the parts store!!

The rectifier assembly is the internal device that converts the ac current output of the alternator to a dc current for use in charging the battery.

While the partially-failed alternator will continue to charge a battery in "daytime" mode, it's charging rate is going to be a lower than it should be. So therefore, most shops just "call it good".

The simplest methodology for detecting the "current draw" situation you describe...rig a simple 12vdc test lamp between the battery positive post and the cable terminal, without having the cable actually connected. If you actually have a parasitic current draw, the lamp will illuminate, even very faintly.

If you do see a current draw, then the next step is individually (one at a time) remove each fuse and determine which fused circuit turns the lamp off. Then home in on all components associated with that particular circuit.
 
michael mayben said:
the most common cause of this issue is an alternator that has a partially-failed rectifier assembly. This will not show up normally in a typical test conducted on a machine at the parts store!!

The rectifier assembly is the internal device that converts the ac current output of the alternator to a dc current for use in charging the battery.

While the partially-failed alternator will continue to charge a battery in "daytime" mode, it's charging rate is going to be a lower than it should be. So therefore, most shops just "call it good".

The simplest methodology for detecting the "current draw" situation you describe...rig a simple 12vdc test lamp between the battery positive post and the cable terminal, without having the cable actually connected. If you actually have a parasitic current draw, the lamp will illuminate, even very faintly.

If you do see a current draw, then the next step is individually (one at a time) remove each fuse and determine which fused circuit turns the lamp off. Then home in on all components associated with that particular circuit.
Click to expand...

These are great ideas. We had gone thru it and we are showing nothing draw more than 0.5amps right now. We are still going thru things individually and still not seeing it. It has been strange. I appreciate your thoughts and we will keep working on it.
 
If you are seeing a 0.5 (1/2) amp draw continuously, then that is your problem!!! Spread that over 24 hours, then 48 hours without actually starting the engine and you will have a battery that measures under the minimal starting capacity.

Unless you have added parasitic loads to the system, there should be no current draw at any time the ignition key is in the off or lock position.
 
michael mayben said:
if you are seeing a 0.5 (1/2) amp draw continuously, then that is your problem!!! Spread that over 24 hours, then 48 hours without actually starting the engine and you will have a battery that measures under the minimal starting capacity.

Unless you have added parasitic loads to the system, there should be no current draw at any time the ignition key is in the off or lock position.
Click to expand...


You are exactly right...I don't think I worded it correctly...we are not finding any draw as low as 0.5amp. We can't find anything. So, we are not sure what is discharging the battery. We will keep on investigating and I will report back. Thanks and if you have any thoughts, I would love to hear it. I appreciate your help.
 
Another issue can be were somebody put the wrong fuse in. The pre 1980 IH took a shorter then "normal" fuse. The slightly longer fuse would spread the ears of the fuse holder enough to touch the fuse holder next to it. Which could send some juice down a circuit that should been off. I don't have a good pic of it, but take a look to make sure none of the ears are touching each other on the fuse holder.
 
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