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I have a battery that has bitten the dust because my truck has developed an electrical short in wet weather. I am going to replace the battery and remove the negative terminal anytime I park anytime it has recently rained. Then after a couple days I will test the current flow when off to make sure it is zero to ensure it is sufficiently dry to again leave the battery connected. Clearly this is preferably a short-term solution, though worth doing to avoid killing another battery.
As for the diagnosis so far, I have tried taking out all the fuses that are easily removable and the ammeter was still showing a significant draw (> 200 mA if I remember correctly) with the car and all the accessories off. I am not sure where the short could be if not in one of these circuits, but the other clue is that over the years I have noticed the stereo lapse into some kind of reverb or echo on occasion and thought this could be none other than an electrical infirmity. It hasn't done this for a while but still think it could be a good hint. I am not using any aftermarket amps other than a Kenwood receiver plugged into the usual harness wires, but maybe there is a way of testing these wires for a short or to see if they are part of one of the aforementioned circuits?
Otherwise, I am suspecting something to do with an old starter motor with a rotor that somehow grounds out on the stator when wet or something of this sort .. any suggestions or known issues with this truck would be excellent.
I have a battery that has bitten the dust because my truck has developed an electrical short in wet weather. I am going to replace the battery and remove the negative terminal anytime I park anytime it has recently rained. Then after a couple days I will test the current flow when off to make sure it is zero to ensure it is sufficiently dry to again leave the battery connected. Clearly this is preferably a short-term solution, though worth doing to avoid killing another battery.
As for the diagnosis so far, I have tried taking out all the fuses that are easily removable and the ammeter was still showing a significant draw (> 200 mA if I remember correctly) with the car and all the accessories off. I am not sure where the short could be if not in one of these circuits, but the other clue is that over the years I have noticed the stereo lapse into some kind of reverb or echo on occasion and thought this could be none other than an electrical infirmity. It hasn't done this for a while but still think it could be a good hint. I am not using any aftermarket amps other than a Kenwood receiver plugged into the usual harness wires, but maybe there is a way of testing these wires for a short or to see if they are part of one of the aforementioned circuits?
Otherwise, I am suspecting something to do with an old starter motor with a rotor that somehow grounds out on the stator when wet or something of this sort .. any suggestions or known issues with this truck would be excellent.
Separate the two paths (junction block and starter) from the battery and go from there.
Starter is a good candidate if the rubber boot is missing. And stereos are always suspect.
There are three notorious suspects for water in the cap. Cowel area, roof drains, and windshield, easy enough to spot when it's happening but maybe hard to isolate a source.
Disconnect alt to batt cable from stud terminal of alternator.
Measure resistance to ground from stud terminal. What do you get?
Reverse test probes. What do you get?
Should be Lots of Meg-ohms.
Stud terminal is shown here (copy and paste whole url to your browser. Yotatech does not like embedded google photo, but yotatech album has no search function so I do not like to use it): https://lh3.googleusercontent.com/0T...=w1015-h761-no
Last edited by RAD4Runner; 01-03-2020 at 10:01 AM.
looking into doing tests on the alternator and starter, though it seems peculiar these components being under the hood would be affected by the rain .. if none of the fused circuits showed a drain, I am guessing the short to ground is somewhere between the fuse box and the battery or in one of these larger systems. Are the alternator/starter on fused circuits? Does anyone recommend one of those induction-based chirping tools for diagnosing parasitic drains?
(Sorry I don't have the schematic handy now)
Alternator "IG", "L" most likely fused. However, "S" wire and "B" (Alt to batt) wire are most likely always connected to battery through the fusible link module which is bolted into the circuit.
See test for alternator stud terminal I posted above.
(on first-gen 4Runners there is an additional inline fusible link wire).
Starter itself is unlikely to cause drain. The starter solenoid completely disconnects it fro battery positive.
Starter positive is thick cable directly to battery positive. Starter negative is that thick cable to engine block directly to battery negative. Unlikely for the positive to drain to starter unless starter solenoid contact closes. It takes aprox 12 amps to close those.
Does anyone recommend one of those induction-based chirping tools for diagnosing parasitic drains?
MEH. multi-meter's good enough.
Last edited by RAD4Runner; 01-08-2020 at 08:53 PM.
indeed, after looking into this a bit further, it seems a bad diode on the alternator is more likely than anything with the starter. ..
1) Disconnect ALL from battery negative.
2) Connect ALL that you disconnected from batt negative together (cable to engine block, wire to fender ground).
3) MM to Amp setting
4) Connect pos probe of MM to (2)
5) Connect neg probe of MM to battery negative. Observe reading.
6) Disconnect alt-to-bat wire "B" from stud terminal of alt like I posted above. See if that makes a difference. (Jump to 2:30 mark of video)
7) If 6 made a difference, either dirt / oil etc causing short to ground or bad rectifier.
Last edited by RAD4Runner; 01-03-2020 at 02:23 PM.
In an effort to keep this thread (and my truck) alive, I finally bought a new lead-acid battery so I could more reliably proceed with looking at alternator performance and ultimately locating the short circuit. Reason for the delay is I was looking into the possibility of building a LiFePO₄ battery for durability and longevity, but in addition to extra time, it wouldn't cost any less, and there was also the detail about limiting the current flow from the alternator due to the lower internal resistance of lithium batteries. Instead I decided to narrow my focus to untethering my truck from a wall socket. Although it has been dry long enough the parasitic drain has likely receded, I made sure to disconnect the negative terminal on a fresh battery.
Originally Posted by jbtvt
Got a leaking windshield dripping onto a relay on your passenger side? First thing I'd do is determine moisture vs water infiltration, put plastic halfway down hood, onto roof and over fenders when it's going to rain again and see if problem goes away. If it does, pull your windshield trim and caulk solid with silicone.
Interesting your mention of a leak in the windshield because I lost the trim on the top and passenger side and subsequently went about cleaning and filling the channel with black construction sealant. This could be a hint to the mystery of the short appearing in the rain, but I am not sure where the relay is located that would be affected by a leaking windshield ..
The windshield trim does not seal the windshield. In fact it hastens corrosion by catching and trapping dirt and moisture. The urethane adhesive (Sika is popular brand) seals the windshield. I deleted my chrome trim.
Interesting your mention of a leak in the windshield because I lost the trim on the top and passenger side and subsequently went about cleaning and filling the channel with black construction sealant. This could be a hint to the mystery of the short appearing in the rain, but I am not sure where the relay is located that would be affected by a leaking windshield ..
They're above the ECU. Blower, circuit opening, couple others. Bunch on the driver's side also and fuses there too. I've had more water issues on pass side though for whatever reason.
Does this only happen when the truck has been driven in the rain or happen even from just sitting? Splash issue, or leak issue?
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though it seems peculiar these components being under the hood would be affected by the rain ..
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Really, because your distributor cap which sits basically at the top of the bay comes with an O ring and even had an additional cover, surprised you think that.
There is a reason we use "weather resistant" connectors in the engine bay. Even with your lower engine cover on, and perfect curtains on the fender to frame gaps, water will get in there!
And nothing kills more alternators faster than a few well placed drips be it rain water or a leak in the power steering..
Hell if someone designed brackets to swap the PS pump's and alternator's positions they would likely have people lining up for them.
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Starter itself is unlikely to cause drain. The starter solenoid completely disconnects it fro battery positive.
Starter positive is thick cable directly to battery positive. Starter negative is that thick cable to engine block directly to battery negative. Unlikely for the positive to drain to starter unless starter solenoid contact closes. It takes aprox 12 amps to close those.
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What happens when that wire to the battery doesn't have its rubber boot and then becomes wet due to oil and water?
This is what I tried to describe.
The answer is continuity from the battery cable to the starter housing. It's a pretty minor drain and not a huge risk, since it is on the bottom face it should run away from the starter housing, but that boots not just there to keep you from shorting the battery wire to ground with oh say your hand.
In an effort to keep this thread (and my truck) alive
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Nothing is more reliable or resilient than wet cell lead acid, the only real down side is they are bulky and heavy, we've been using these for close to a hundred years in everything we can fit them in from various vehicles like cars, boats, and even houses.
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While you have that caulking gun out you should inspect the drip rails above the doors and think about refreshing the panel sealer there. RAD and myself have been bit by that one.
So I put a meter on the parasitic drain and it is showing a full 5A continuous. If not for concern of my 10A meter, I would connect it between the battery posts to see if it's about the same current, which would connote a more direct short to the frame rather than through some part or winding. As mentioned, I already tried pulling all the fuses under the hood and in the driver's side panel without vanquishing the drain, so the short must either happen before a fuse or in an unfused circuit, though I am guessing all circuits are either interrupted by a fuse or relay?
Originally Posted by jbtvt
They're above the ECU. Blower, circuit opening, couple others. Bunch on the driver's side also and fuses there too. I've had more water issues on pass side though for whatever reason.
Does this only happen when the truck has been driven in the rain or happen even from just sitting? Splash issue, or leak issue?
This means there is suspect componentry behind the glove and right speaker I ought uncover? I am not sure if the parasitic drain appeared after driving in the rain, but at this point it seems to be more or less lingering full-time.
I have yet to locate the alternator and remove the post here to see if the drain is affected -- I will look into an alternator swap now. The stereo has also produced abnormal audio over the years as mentioned, and I would like to get at anything related to this that might be hardwired, although nothing aftermarket other than the receiver and some 6" door speakers. If I pull the harness from the receiver, perhaps a current test between some of the hot wires here and ground is useful?
Everything is fused in one way or another, so what is still connected to the battery?
I can't remember if the 90's era had the alternator junction on the fender the 80's ones have, it's really easy to.get to if you do..
Oh PS, don't do a current draw between a hot wire and ground like that that'll blow your meters fuse.. BTW your meter has a 10amp fuse on the current measuring lead, in most cases it's a cheap barrel fuse.
How many amps would a meter with enough capacity measure between the posts of a fully charged lead-acid battery?
Between posts of a battery is a dead short. The battery can provide 600 or so cranking amps. No multi-meter will survive that.
Originally Posted by Co_94_PU
...don't do a current draw between a hot wire and ground like that that'll blow your meters fuse.. BTW your meter has a 10amp fuse on the current measuring lead, in most cases it's a cheap barrel fuse.
See this?^^^^
Have you done as I suggested that u measure resistance from stud terminal of alternator to ground?
Why do you ask for our help if you're gonna go ahead with experimentation before doing the simple, basic and FREE checks we suggest?
Last edited by RAD4Runner; 01-10-2020 at 01:54 PM.
At this point the truck has been dry long enough the parasitic drain has gone. Another current test connected as before shows 1.5A for a few seconds before dipping down into the double-digit milliamp range. A resistance test between the 10mm post on the alternator and the frame stays at 1 except on the continuity setting, which stabilizes at 1.9.
12-29-2019, 11:56 AM
