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Alternator cause of parasitic drain. Help!

5K views 15 replies 8 participants last post by  RevDrCueBall 
#1 ·
Re-correcting the wiring in my engine compartment, and so far, it's going well. However, I've had a parasitic drain on my battery for a while, and I've just kept the negative battery cable un-hooked when I was going to let it sit for a while. I decided to finally track that down.

Bought a test light, and hooked it up between the unhooked negative cable and the negative battery terminal with ignition off. Bright light shines in the engine bay!

After pulling fuses, connectors, etc for a while, I finally come to the Alternator that the PO had wired like the picture below. Unhooked the small black (excite wire?) and the test light got a lot dimmer. Unhooked the jumper wire that goes to the #2 terminal, and the light goes out. Either of these wires on either post 1 or 2 seem to create a parasitic draw on the battery.

Aside from the excite (?) wire being connected to the wrong place, it seems that if I hook it up correctly, per my searching, I would still get a battery draw.
I've took my VM and tested for simple connectivity between post 2 and ground (the case). None. Tested connectivity between post 1 and the case and there is connectivity.

Is there a short in my alternator causing this draw, or am I missing something else?
Is there a way to test for an internal short in the alternator with a VM?
 

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#2 ·
I see the red wire connected, Was there anything on the other terminal?
Was someone trying to convert this to a 1 wire hookup?

http://mightymo.org/Proj_OneWire.html

There seems to be a resistance to ground on the other terminal but I don't know the value.


IF it was hooked up correctly there is a fix were you put a diode inline with one of the wire.
 
#4 ·
I see the red wire connected, Was there anything on the other terminal?
Was someone trying to convert this to a 1 wire hookup?

There seems to be a resistance to ground on the other terminal but I don't know the value.

IF it was hooked up correctly there is a fix were you put a diode inline with one of the wire.
There was nothing on the other terminal.

If I'm reading you right: and assuming the Alternator isn't shorting internally or a bad diode, theoretically, I should hook up the small dark wire to the empty terminal with an in line diode, and be good to go, correct?

Sounds like a bad diode inside.....couple ways to check (neither of which have I used BTW). Set your multimeter to a low AC setting, start the jeep and put the leads on the battery terminals......if you get any kind of AC ripple over 0.5V then the diode(s) are likely the problem. The other way to check is to unhook all the wires and put the meter in "diode test" (see pic). Then probe the regulator stud and the housing......then reverse the leads and probe again. If you get low readings (0.2 etc.) that is confirmation that the diodes are toast.
If I get a low reading both ways or just one way? (Haven't tried yet, but will this evening)
 
#3 ·
Sounds like a bad diode inside.....couple ways to check (neither of which have I used BTW). Set your multimeter to a low AC setting, start the jeep and put the leads on the battery terminals......if you get any kind of AC ripple over 0.5V then the diode(s) are likely the problem. The other way to check is to unhook all the wires and put the meter in "diode test" (see pic). Then probe the regulator stud and the housing......then reverse the leads and probe again. If you get low readings (0.2 etc.) that is confirmation that the diodes are toast.

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#5 ·
Sounds like a bad diode inside.....couple ways to check (neither of which have I used BTW). Set your multimeter to a low AC setting, start the jeep and put the leads on the battery terminals......if you get any kind of AC ripple over 0.5V then the diode(s) are likely the problem. The other way to check is to unhook all the wires and put the meter in "diode test" (see pic). Then probe the regulator stud and the housing......then reverse the leads and probe again. If you get low readings (0.2 etc.) that is confirmation that the diodes are toast.
OK, I did Method 2 using the diode test mode.

Testing Bat Stud to Case:
Black probe on Stud and Red on Case reading: 0.81
Red probe on Stud and Black on Case reading: 1.00
Sounds like a bad internal diode? and a small drain? New Alternator?

Testing Prong/Terminal 1 (excite wire connection?):
Black probe on Terminal 1 and Red on Case reading: 0.044
Red probe on Terminal 1 and Black on Case reading: 0.044
This tells me here is a significant drain here as well, but a diode in line in the wire would solve this, yes?

Testing Prong/Terminal 2 (voltage sensing wire connection?):
Black probe on Terminal 2 and Red on Case reading: 1.00
Red probe on Terminal 2 and Black on Case reading: 1.00
No connectivity means this one isn't a problem.

Thoughts?
 
#7 ·
I thought the same after I rewired my 74. Checked every circuit by removing each fuse. Didn't go away. Thought maybe I had two open circuits. I removed all fuses and to check each circuit by itself and still had a draw. Replaced the alternator under warranty and still had a draw. Whiskey Tango Foxtrot! Then the dumb arse holding the meter remembered I had to rewire the light switch because the tail lights won't go off. The circuit to the switch is unfused because each light circuit coming off the switch is fused. A bad switch can cause a draw and is undetectable using standard trouble shooting.

FYI I still use the quick disconnect to remove the negative cable when I return the beast to its stall. This meets the insurance requirement for a secondary disabling device.
 
#8 ·
Arrrgggghhh!

Still need help!

Replace Alternator, bought all new components to wire it in properly. Got the proper pigtail connector, wires, fusible link, dedicated ground, and the diode from radio shack. Wired it just like this without the indicator lamp, except I ran the excite wire to the I terminal of the starter solenoid (also new):



My test light tells me I am still getting a battery draw!?!?!

So if I unplug the bat terminal and the pigtail, the test light goes out. Means I've still got a short from one or the other inside the alternator? Seem unlikely with a new one. What am I missing?

Wired as such:
 

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#9 ·
Not sure, but tagging for what you find.
 
#10 ·
Upon reading JeepHammer's advice on alternator wiring theory, I tested that nether the Batt wire nor the excite wire (after installing the diode) were the cause of the parasitic draw. I then used his advice to run the "sense" wire somewhere closer to the load end of the wiring on an ignition switched source instead of the hot side of the starter solenoid.

I chose the large 10 Ga ignition wire coming out of the bulkhead connector (the one that goes down to the ICM). That took care of the parasitic drain, but when I turn on the key, I get a strange buzzing noise from the passenger side of the engine for about 5-10 seconds. Since it doesn't last long, I can't pinpoint it. Still starts and runs fine. Seems to charge fine, but I don't like the buzzing... I feel like it's coming from the coil or the dizzy, but no way to verify that.

I've got an new HEI dizzy in the shed that I'm going to drop in and take out the ICM/stock coil and dizzy and see what that does.

Anyone got any thoughts????
 
#15 ·
Looks like you're solving the problem. I just wanted to put in my 2 cents. On my 84 I have a 2 wire connector that plugs into the alternator and one ofor the wires is like a resistance wire. I think the wire is brown. And the conductor looks like solder frome a roll of solder . You don't have this wire ? Reason I ask is because this wire had come out of the spade terminal and the jeep wouldn't start after it sat for a while.
 
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