Battery draining

4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
Do you have a good multimeter? Do you know how to use one? It’s time to divide and conquer with your fuses to point you in the right direction. It could also be your alternator. Would need to know how proficient you are with electricity before I give step by step advice. Wouldn’t want you to start arc welding or a fire. Lol
 

terryjm1

Well-known member
Jan 23, 2011
1,486
375
Pull a fuse one at a time and see which circuit is drawing power when it shouldn‘t, correct?

I have a slow drain on my battery as well but it takes longer than a couple days. It hasn’t made it to the top of the list for diagnosis as of yet.
 

SGaynor

Well-known member
Dec 6, 2006
7,148
162
52
Bristol, TN
Disconnect the negative battery cable. Connect one end of the multimeter (set to amps) to the negative battery post and the other to the battery cable.

You'll see an amperage reading. That's the drain on the battery.

Start pulling fuses one at a time and check the amps being drawn. When you see one drop, note it. Do all of them (unless you find one that drops the amp draw significantly). Then get the Rave manual and look at the electrical diagrams for the circuit that that fuse(s) are on. Then start looking for shorts on the actual truck tracing the lines based on the electrical diagram.
 

mlnnc

Well-known member
Mar 23, 2008
266
31
Charlotte
Did the truck once have air springs (SLS) in the rear that were replaced by coils? Using a multimeter is the best way to diagnose parasitic drains on the battery, but if the truck had air springs swapped for coils that is a clue and a common reason for the problem.
 

Briany

Member
Nov 20, 2019
12
4
Ireland
I'm having the exact same issue, but am maybe a little way ahead of you in diagnosing it. I did the recommended connecting of a multimeter across the battery negative terminal to check for current flow, and indeed I have in the region of 330mA being drawn. So, on to the fuse pulling:
1. At first, the amperage was all over the place, till I remembered that the interior lights are on a timer, so kept trying to draw current, then resetting, then trying to draw it again. So I pulled the 6A fuse (#1 in Satellite fuse box 1, I think) that governs them. The drain was steady at about 330mA after this.
2. Progressively pulling all the fuses in the under-dash fusebox I found two small drains - both auxiliary fuses (one was #15, can't remember the other - it was in one of the satellite boards). But both were only drawing 10-20 mA. Not enough to explain the big drain.
3. No other circuits governed by the under-dash fuses seemed to be causing the drain, so I moved to the fuse box in the engine bay.
4. Pulled all the small fuses one by one - no change to the drain. Moved onto the big (60-100A) fuses in the same box, but held in place by screws.
5. Pulled the 100A fuse governing the alternator (according to the legend on the inside of the fusebox). Bingo! Drain dropped down to a negligible level.
6. Right, it must be the alternator. Let's google the crap out of it. Yes, it seems that when the diode pack is getting worn it starts to leak current. This is looking plausible.
7. New alternators are expensive, although I might be able to clean the existing diode pack (saw a post that said carbon dust from the brushes can cause leakage), or replace just the pack.
8. Disconnected the three wires, opened the back of the alternator (in situ), sprayed in a bunch of electrical circuit cleaner, let it dry, and tested for current drain again. Still draining 330mA. Bugger.
9. For the hell of it, and cos I was messing with the alternator anyway, I disconnected each of the three wires one-by-one and tested after each to see was the drain linked to any particular one. First one off - still 330mA drain. Second one off - still 330mA. Third one gone - now the alternator is completely disconnected electrically, it must be solved. Nope, still a 330mA drain.

So this is where I am. I have a drain of a third of an Amp that's running through the 100A fuse that supposedly governs the alternator. But it ain't the alternator. So that's the big question. What else is connected to that 100A fuse - either intentionally or unintentionally?

Anyone have any experience of this? Google hasn't been much help (yet). My next thought is to disconnect the starter solenoid. And before anyone suggests it, I know that RAVE might answer it, but I'm pretty poor at figuring it out. I'll decipher it eventually if I need to, but it'd be great if someone had experience of this.

PS, new member here. Hi everyone. This is my first Disco, though I have two SIIIs, so it's not quite my first rodeo. All this electrical hoo-haa is a bit new, though.
 
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ankeneering

Active member
Apr 21, 2017
41
3
wyoming
I'm having the exact same issue, but am maybe a little way ahead of you in diagnosing it. I did the recommended connecting of a multimeter across the battery negative terminal to check for current flow, and indeed I have in the region of 330mA being drawn. So, on to the fuse pulling:
1. At first, the amperage was all over the place, till I remembered that the interior lights are on a timer, so kept trying to draw current, then resetting, then trying to draw it again. So I pulled the 6A fuse (#1 in Satellite fuse box 1, I think) that governs them. The drain was steady at about 330mA after this.
2. Progressively pulling all the fuses in the under-dash fusebox I found two small drains - both auxiliary fuses (one was #15, can't remember the other - it was in one of the satellite boards). But both were only drawing 10-20 mA. Not enough to explain the big drain.
3. No other circuits governed by the under-dash fuses seemed to be causing the drain, so I moved to the fuse box in the engine bay.
4. Pulled all the small fuses one by one - no change to the drain. Moved onto the big (60-100A) fuses in the same box, but held in place by screws.
5. Pulled the 100A fuse governing the alternator (according to the legend on the inside of the fusebox). Bingo! Drain dropped down to a negligible level.
6. Right, it must be the alternator. Let's google the crap out of it. Yes, it seems that when the diode pack is getting worn it starts to leak current. This is looking plausible.
7. New alternators are expensive, although I might be able to clean the existing diode pack (saw a post that said carbon dust from the brushes can cause leakage), or replace just the pack.
8. Disconnected the three wires, opened the back of the alternator (in situ), sprayed in a bunch of electrical circuit cleaner, let it dry, and tested for current drain again. Still draining 330mA. Bugger.
9. For the hell of it, and cos I was messing with the alternator anyway, I disconnected each of the three wires one-by-one and tested after each to see was the drain linked to any particular one. First one off - still 330mA drain. Second one off - still 330mA. Third one gone - now the alternator is completely disconnected electrically, it must be solved. Nope, still a 330mA drain.

So this is where I am. I have a drain of a third of an Amp that's running through the 100A fuse that supposedly governs the alternator. But it ain't the alternator. So that's the big question. What else is connected to that 100A fuse - either intentionally or unintentionally?

Anyone have any experience of this? Google hasn't been much help (yet). My next thought is to disconnect the starter solenoid. And before anyone suggests it, I know that RAVE might answer it, but I'm pretty poor at figuring it out. I'll decipher it eventually if I need to, but it'd be great if someone had experience of this.

PS, new member here. Hi everyone. This is my first Disco, though I have two SIIIs, so it's not quite my first rodeo. All this electrical hoo-haa is a bit new, though.
this is a d1 or a d2? youve done a lot of research here and Id love to know more from someone whose been in this position before.
 

Briany

Member
Nov 20, 2019
12
4
Ireland
Mine's a 1997 D1 ES auto - japanese import (I'm in Ireland).

The latest is that I checked all the other fuses in the box under the hood also - bingo, lifting one of the large (screwed down) 60A fuses - the one governing the "W/Lift, CDL and Rear Blower" (window lift, central door locking) also stops the drain. From my limited skill in reading the circuit diagrams, it appears that the 100A fuse leads also to that fuse, so I've narrowed it down to these options (unless that fuse covers some other items also).
Right, time to start pulling plugs and other fuses. I disconnect each of the door electrics by turn, and keep measuring the current drop - no change for any of them (including the rear door).
I also pull the relevant fuses governing the windows, locking and blower (doesn't specify front or rear - just an icon of a fan) in the main under-dash fuse board (even though I'd checked these already). No change.

Interestingly, I realise that when all doors are closed the drain goes from 330mA to 180mA - even though I've removed the fuse for the interior lights. Obviously there's current leakage at one or more of the spring door switches. Next step to disconnect each of these in turn to see if it's any particular one, or somewhere further in the innards of the electrics.

So the prime suspect at the moment, by process of elimination, is the rear blower. But my truck was converted to a commercial - all the rear interior was stripped out. Where oh where do I find the electrics for the rear blower? Can anyone point me in the right direction?
 

CORover

Well-known member
Jun 11, 2007
745
65
Colorado, USA
Might try looking at the elec troubleshooting diagrams that WaltNYC has in his sig line. Tough to get through sometimes but if you keep at it you will find a wealth of info that eventually makes sense.
 

Levi

Well-known member
Jul 27, 2004
559
26
Cheyenne, WY
Mine's a 1997 D1 ES auto - japanese import (I'm in Ireland).

The latest is that I checked all the other fuses in the box under the hood also - bingo, lifting one of the large (screwed down) 60A fuses - the one governing the "W/Lift, CDL and Rear Blower" (window lift, central door locking) also stops the drain. From my limited skill in reading the circuit diagrams, it appears that the 100A fuse leads also to that fuse, so I've narrowed it down to these options (unless that fuse covers some other items also).
Right, time to start pulling plugs and other fuses. I disconnect each of the door electrics by turn, and keep measuring the current drop - no change for any of them (including the rear door).
I also pull the relevant fuses governing the windows, locking and blower (doesn't specify front or rear - just an icon of a fan) in the main under-dash fuse board (even though I'd checked these already). No change.

Interestingly, I realise that when all doors are closed the drain goes from 330mA to 180mA - even though I've removed the fuse for the interior lights. Obviously there's current leakage at one or more of the spring door switches. Next step to disconnect each of these in turn to see if it's any particular one, or somewhere further in the innards of the electrics.

So the prime suspect at the moment, by process of elimination, is the rear blower. But my truck was converted to a commercial - all the rear interior was stripped out. Where oh where do I find the electrics for the rear blower? Can anyone point me in the right direction?


It's probably not this based on your troubleshooting but I thought I would mention it since it is easy enough to check. Make sure your glove box light is turning off when it's closed. Mine was staying on all the time and draining the battery.
 

mc9735

Active member
Apr 29, 2017
41
3
Chattanooga
Mine's a 1997 D1 ES auto - japanese import (I'm in Ireland).

The latest is that I checked all the other fuses in the box under the hood also - bingo, lifting one of the large (screwed down) 60A fuses - the one governing the "W/Lift, CDL and Rear Blower" (window lift, central door locking) also stops the drain. From my limited skill in reading the circuit diagrams, it appears that the 100A fuse leads also to that fuse, so I've narrowed it down to these options (unless that fuse covers some other items also).
Right, time to start pulling plugs and other fuses. I disconnect each of the door electrics by turn, and keep measuring the current drop - no change for any of them (including the rear door).
I also pull the relevant fuses governing the windows, locking and blower (doesn't specify front or rear - just an icon of a fan) in the main under-dash fuse board (even though I'd checked these already). No change.

Interestingly, I realise that when all doors are closed the drain goes from 330mA to 180mA - even though I've removed the fuse for the interior lights. Obviously there's current leakage at one or more of the spring door switches. Next step to disconnect each of these in turn to see if it's any particular one, or somewhere further in the innards of the electrics.

So the prime suspect at the moment, by process of elimination, is the rear blower. But my truck was converted to a commercial - all the rear interior was stripped out. Where oh where do I find the electrics for the rear blower? Can anyone point me in the right direction?
Hey there - I have the same issue it sounds (I've so far isolated the parasitic draw to the 60A fuse under the hood: W/Lift, CDL and Rear Blower). I removed all the related fuses under the dash...no change, still drawing >200mA. Were you able to solve your issue? I'm tempted just to throw a knife switch on the battery to deal with it (will prob do regardless as truck sits alot).

A couple other things I should mention in case it helps diagnose: truck is new to me ('94 DI) and has known electrical issues (doors won't lock/alarm doesn't work, radio doesn't work, one of the windows still doesn't go up (fixed the others)). I have no idea if these items could be related... I use it as a trail truck, so no big deal for me.

Appreciate any help you or others can offer!

Mike
 

mc9735

Active member
Apr 29, 2017
41
3
Chattanooga
Hi Robert - alternator diode pack...what would make you say that? how could I test to validate that theory? Alternator seems to be charging just fine at 14+ voltage while running.
 

robertf

Well-known member
Jan 22, 2006
4,778
354
-
Unplug the cable from the alternator and check the current draw with the engine off

Sometimes you can even hear a high pitched hissing noise when everything is off
 

mc9735

Active member
Apr 29, 2017
41
3
Chattanooga
...one more thing to add: when I reconnect the negative terminal, I hear a faint mechanical noise for maybe 5 seconds, coming from inside the dash...guessing this has something to do with the blower? maybe a pump or something? I'm assuming it's tied to a circuit from 60A fuse "W/Lift, CDL and Rear Blower"
 

mc9735

Active member
Apr 29, 2017
41
3
Chattanooga
Robert - I don't know if this is worth anything, but they tested my alternator at an Auto Zone and reported it was fine (whatever that means). I'm assuming i still need to test for current draw as you're suggesting? Sorry, I'm pretty green at this...