Troubleshooting Parasitic Draw - Page 3 - Defender Source
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  #41  
Old August 29th, 2014, 07:39 AM
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Perhaps you need to have the alternator checked again. If possible, swap in another alternator to eliminate that as the potential draw.
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  #42  
Old August 29th, 2014, 08:32 AM
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This is with everything in the truck off, correct?

If so, definitely a bad diode in the alternator. Diodes are essentially "one way valves" that are supposed to only allow current to flow from the alternator to the battery. When one fails, and the alternator is producing less current than is available at the battery (engine not running), a bad diode will allow voltage to flow backwards through the system and essentially tries to drive the alternator like an electric motor (in basic terms).

This rebuild shop owes you a refund! And maybe more considering the extra stress this has put on your battery.
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  #43  
Old August 29th, 2014, 08:43 AM
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Agreed. This can then lead to burned coils in the alternator, which would then again fail.

Either the diodes were never replaced or the wrong ones were used.
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  #44  
Old August 29th, 2014, 11:02 AM
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By the way, the figure .008 after alternator disconnected is right in line with what the truck should draw.
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  #45  
Old August 29th, 2014, 11:07 AM
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If it is a bad alternator diode, then the rectifier circuit won't work properly and you will be bleeding A/C into your system, correct? You should therefor see some A/C coming out of the alternator. Switch the meter to A/C and see what you get. It is something that an alternator tester can check pretty easily.

I am still not sure about the meter reading as I am not familiar with such high tech wizardry as that Snap On. If it is indeed 1A, then crap, that is huge. 1mA and you are golden. I have had a blown zenier diode before and with the truck off I was not experiencing that loss, but that was my scenario. The A/C bleed was causing my fuel injectors to misfire at 2700 rpm and that is how I tracked my issue down. I don't know if different blown diodes (I believe there are 3?) would cause draw or not--just not my area of specialty.

So, what I am gathering is your new battery still drains over night after everything you have done, correct? That certainly points to 1A draw to me. You remove the brown wire and this goes away, correct? To me, that points to 4 possible components (I have not looked at my wiring diagram)--those components I believe would be your solenoid, your starter, your alternator, and possibly your wiring.

It could potentially be possible, although I have never seen this happen, that you have a frayed wire that is grounding to your chassis--this would be the most unlikely scenario to me, but still theoretically possible.

I have never seen a solenoid fail any other way than open--so I doubt that. Starter? Never seen an open condition. But if you alternator checks out, that would be on my list...
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  #46  
Old August 29th, 2014, 11:33 AM
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If disconnecting the power cable from the alternator causes the draw to go away, it is definitely the alternator. There is no way that disconnecting that cable would change anything at the starter to stop a draw condition.

And you are right, I have never seen a starter solenoid fail closed - if it did, it would fail closed so that the starter was engaged (motor spinning) 100% of the time.

Based on the knowledge we have now I can confidently say the alternator is bad.
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  #47  
Old August 29th, 2014, 06:14 PM
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Took the alternator back to the shop - again. For good measure I exhausted every other possible scenarios down to the starter. Completely isolated the problem to the alternator. Shop is cool, local LR club swears by them. They put my alternator on the test bench and found bad diodes.

Lets hope this is the end of the problem!

Thanks for the insight, opinions, and suggestions. I'll let you know next week if this solved the problem.
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  #48  
Old August 31st, 2014, 02:54 PM
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With the expectation that the alternator will no longer cause the battery drain, there was one other thing I forgot to ask the forum about.

There's something drawing current at the fuse for the emergency flashers. When the fuse is pulled, I'm at 0.008 on the DMM, but when that fuse is in, it goes up to 0.032

First, is this small of a draw going to cause problems?

I eliminated both the dash switch and the relay as the problem, and tested the continuity from the switch to the fuse. I get a small spark when I put the fuse in, if that helps with any diagnosis. I'm tempted to just yank the fuse and leave it out, but it couldn't hurt to ask the group.

Thanks
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  #49  
Old August 31st, 2014, 03:41 PM
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Quote:
Originally Posted by founD90 View Post
With the expectation that the alternator will no longer cause the battery drain, there was one other thing I forgot to ask the forum about. There's something drawing current at the fuse for the emergency flashers. When the fuse is pulled, I'm at 0.008 on the DMM, but when that fuse is in, it goes up to 0.032 First, is this small of a draw going to cause problems? I eliminated both the dash switch and the relay as the problem, and tested the continuity from the switch to the fuse. I get a small spark when I put the fuse in, if that helps with any diagnosis. I'm tempted to just yank the fuse and leave it out, but it couldn't hurt to ask the group. Thanks
Did you remove the emergency flasher switch ... That may be faulty ... Or perhaps the flasher relay. To be honest it's at the level not to worry about.

Could maybe the radio backup .. As an after thought.
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  #50  
Old August 31st, 2014, 07:08 PM
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Quote:
Originally Posted by leastonce View Post
Did you remove the emergency flasher switch ... That may be faulty ... Or perhaps the flasher relay. To be honest it's at the level not to worry about.

Could maybe the radio backup .. As an after thought.
The emergency flasher has a relay and a switch, independently I tested both and neither are the reason for the drain. Only thing I didn't try was removing both at the same time and testing. If the draw is nothing to worry about, I'll try not to.

Thanks
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  #51  
Old September 2nd, 2014, 07:22 AM
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I wouldn't worry about it. You might have some accessory wired in line with your flasher's power source.
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  #52  
Old September 2nd, 2014, 08:00 AM
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Not a huge concern (draw wise) but interesting. If someone has a link to a 94 NAS wiring diagram or ETM I would like to take a look.
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  #53  
Old September 2nd, 2014, 04:32 PM
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Quote:
Originally Posted by transientmechanic View Post
Not a huge concern (draw wise) but interesting. If someone has a link to a 94 NAS wiring diagram or ETM I would like to take a look.
Thanks for all the suggestions and help Adam. I don't have a '94 wiring diagram, just a '97 which should be similar. Best I can figure, the fuse only goes to the relay, and to the switch. Strange that even with both those items removed the draw remains. Nothing extra is wired to the circuit AFAIK. Makes me wonder if it's simply a wire rubbing against metal somewhere.
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  #54  
Old September 2nd, 2014, 05:33 PM
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Originally Posted by founD90 View Post
Thanks for all the suggestions and help Adam. I don't have a '94 wiring diagram, just a '97 which should be similar. Best I can figure, the fuse only goes to the relay, and to the switch. Strange that even with both those items removed the draw remains. Nothing extra is wired to the circuit AFAIK. Makes me wonder if it's simply a wire rubbing against metal somewhere.
well if all of your switches work in the truck then its going to be something that is 'always on'

I'd inspect anything near the exhaust manifold for melting, then I would check the cig lighters, any aux lighting, and the wiring for rodent damage (especially the positive lead coming from the battery)
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  #55  
Old September 2nd, 2014, 05:40 PM
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You're welcome - I'm glad to help. I've been through the wringer on a few parasitic draw issues.

If there is a real short (like bare wires rubbing on metal) it would very likely blow the fuse or cause a much more significant draw.

97 may be similar but I'm not sure... there is a lot thats different in the driveline which would affect the chassis harness.
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  #56  
Old September 2nd, 2014, 05:59 PM
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my guess is a very small inductive load.

try removing all relays and see if it goes away.

other possibility is an ecu or other control box. any gauges working with the power off?
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  #57  
Old September 2nd, 2014, 06:03 PM
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Quote:
Originally Posted by Jtomchik View Post
well if all of your switches work in the truck then its going to be something that is 'always on'

I'd inspect anything near the exhaust manifold for melting, then I would check the cig lighters, any aux lighting, and the wiring for rodent damage (especially the positive lead coming from the battery)
Thanks Jason. No rodent damage, all the wiring is fine with the exception of the minor draw on the emergency flasher circuit, very localized to the section between the fuse and the relay I believe. I'm not terribly worried about it.

Trust me, last week every major system/wire/fuse/component/relay was tested, re-tested and validated before I concluded that the alternator was still bad even after repair(it was a bad diode as mentioned earlier in this thread).

This one is truly a "it would be nice to find" but not a huge deal.

Thanks
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