slight (but constant) electrical short

[jbrush]

hi folks,

well, it's been a saga, as previous posts will attest. now this. short version: i go to get the van warmed up after maybe 2 months sitting; previously started fine and no issues with electrical. this time: nothing at all, no lights, no click. i put a plug-in starter on it, and all the lights were on super bright but clicking and when i try to crank there's clicking in the dash etc. obviously, i stop that.

the battery has been drained to 2V. (ouch.) removing the three leads off the positive post, i can tell that one of them, the 2.0L fusible link one i think, is shorted a bit. when it's connected, the voltage across the battery goes down about 0.5V. when i check resistance against ground, it's got about 60 kohm; everything else is clean. i went over to the positive screw box (little access port for positive lead) under the "hood", and can confirm that the short is not in the cable from there to the battery.

i looked at the alternator connectors, but it looks in remarkably good shape -- the alternator looks like it's not more than a couple years old, as well. and my thinking is that a problem there wouldn't show as a short?

any ideas about how and where to test further? don't want to just start pulling everything apart if there's a likely spot.

the one thing i did before all this was to put in new dome lights. i fiddled with the fuses doing that, but i've removed all fuses one by one and none of them eliminate the short.

at least it's persistent and detectable without load!

ideas? thanks, y'all. without this site i'd be pretty morose. sad enough as it is.

.brush

[jbrush]

hi folks,

well, i'm kind of perplexed about this short. i've removed all the fuses, and all of the breakers and relays near th fuse box i could reach. still get around 55 kiloohm short between the positive and ground. fwiw, i've disconnected the positive pole in the little square plastic box in the engine area, and the short is on the "forward" side (ie. not between there and the battery).

so what is this likely to be? alternator? is there a good way to access the alt. without jacking up the vehicle?

if not the alt., what could it be? point me to resources on fixing this kind of constant high-resistance short?

thanks, y'all!

[Burntboot]

I am sure that Tim will be along shortly to answer this properly but in the meantime....
Inside your alternator are some little devils called diodes, basically like a one-way valve.
When they burn out, they will cause a drain on the battery.

Don't know how much fun replacing an alternator on a 2wd is, but is doable on a 4wd on under an hour, no jack required.
2wd should be even easier.

As far as alternators go, either go OEM or source a Denso rebuild, best to stay away from the others unless you enjoy changing alt's on a regular basis.
BB

[timsrv]

Yep, sounds like a shorted diode in the alternator. There's several threads here about the alternator. If you're up for it you can save money by just replacing the diode block inside. Here's a thread that shows how it all comes apart: http://www.toyotavantech.com/forum/s...lternator-woes

PS: Here's some info on this issue from another thread:

Based on your description, I think you likely have a shorted diode in your alternator. An alternator with a shorted diode will still charge, but it will allow current to flow both ways. This means it will suck the power back out after the van is shut off. If the previously outlined checks are inconclusive, then go to the little black + box (drivers side engine compartment near the MAF) and disconnect the big wire going into it (that's your alternator output cable). If the load goes away with that disconnected then your problem is in the alternator. Good luck. Tim

PS: A shorted diode will pull about 5 - 10A, so if you're detecting that kind of draw I'd bypass the other checks and go right to the alternator test. Be careful not to ground out any wires when messing with the + box. Be aware that steel tools conduct electricity .

[jbrush]

ok, some progress! i removed the positive wire from the alt. (10mm nut) and now the short goes up to ~500 kiloohm (very variable), which order of magnitude difference leads me to think something's definitely wrong in the alt.

i'm trying to remove it the "4wd" way, as per llamavans's awesome instructions, but i'm stuck right away with lifting the coolant reservoir straight up! i've pulled and wiggled so hard i'm concerned about breaking the metal flange. any secrets? i've tried PB blaster, letting it sit a spell, but it seems stuck.

otherwise, the plan is to remove the (recently refurbed) alt, which doesn't have any visible power steering contamination, and test it further. not sure exactly what to look for. it looks like the diodes are pretty easy to replace with solid ones from the junkyard? any more specs on which are the best vehicles to lift from (honda, toyota models/years)?

thanks much, hoping to get this thing running again soon.
.b

[timsrv]

On a 2wd it's easier to remove from the bottom. Drive it up on some ramps or jack the front. Disconnect the battery before dropping the alternator so you don't accidentally arc it on something. I will usually pull the mount screws then let it hang on the harness. It's easier to disconnect the harness from underneath AFTER the mount bolts are removed.

The recovery tank can get stuck but it's all in the technique. Strong and steady upward force with a little sideways wiggle will always win. If the bracket bends it can be straightened later. Tim

[jbrush]

all right, i'm perplexed.

short version: i got a new alternator, but it ALSO has a "short" between the positive terminal and the ground. what's up?

longer update: i finally removed the old alt., from beneath -- it took some creative jimmying because the pivot bolt was pretty stuck. anyway, i tested from the positive post to the chassis with the alt completely disconnected, and the 60 kilo ohm resistance remained. i figured this definitely meant an internal short, since there's no way there should be that kind of electrical connection. (right?)

so i got a new alternator, which arrived a day or so ago. but in preparing to insert it, i tested the positive pole to chassis, and still get a short! this time it's 40 kilo ohms -- even worse! unless there's something basic about about alternators i don't understand -- completely possible. for what it's worth, the resistance is the same regardless of which direction the probes are (re: diode issue).

any ideas? maybe i should just install the new alternator now that i have it and see if the battery drains, but that's not the friendliest thing to do to a battery if there's really still another problem somewhere.

thanks!

[timsrv]

Maybe you know something I don't, but to me kilo ohms in this area means nothing. It's all about draw. If you want to test the alternator for draw before installing it, ground the alternator case to the negative post of a battery then hook up the big alternator terminal to the positive post (with your meter in series). Set your meter to DC amps and read the actual draw right from your meter (should be zero). Tim

[jbrush]

thanks for the clarification, tim. so i went ahead and did this test, and i read only a very small draw in both the old and new alternators! old alt: 0.41 milliamps; new alt: 1.10 milliamps.

but this amount of very slight draw seems to be normal.

it seems to me that either: 1) the old alt. is actually good; or 2) the old alt. is bad in some way not tested by this test.

my multimeter sees no continuity in the system, now that the alternator is removed. so there's no evidence of another source of draw.

i'm tempted to just put in the new alternator and see what happens when i start the van. are there any major concerns with this approach?

thanks, all!

[timsrv]

If your measurements are correct neither one has a short. FYI a milliamp is only one one thousandth of an amp (.001). An acceptable amp draw on a vehicle battery is .05 (50 milliamps) with a preferred amount of less than .03 (30 milliamps). Example: a standard automotive battery with a 50 milliamp draw would take approx 9 1/2 weeks to run dead. A 30 milliamp draw would take about 4 months. A one milliamp draw would take over 9 years (assuming self discharge wouldn't drain it before that .

It's still possible your old alternator is defective (just not shorted). You could have an "open" diode, and that could allow for some alternator output, but not enough to compensate for normal loads while driving. Where does your battery voltage hover at when the van is running? Tim

[jbrush]

It's still possible your old alternator is defective (just not shorted). You could have an "open" diode, and that could allow for some alternator output, but not enough to compensate for normal loads while driving. Where does your battery voltage hover at when the van is running? Tim

that's just it -- last time i tried it didn't even run long enough to check. ie. i put in a new battery, fully charged, and started the van. within about five minutes the van cut out, and wouldn't even turn over to restart it, and the battery voltage was down to around 11-ish volts (iirc). so i assumed there was some fairly major short, tested for continuity, and got the approx. 45 kiloohm resistance i discussed above.

of course, now that i actually calculate it out, 45000 ohms would take a 50 A-h battery 187,500 hours to discharge. so i've kind of been chasing after a shadow. oops.

then, here's my major question: why, when i started the van, did it suddenly drain the battery?

i guess the next thing to do is to install the new alternator and see if the same thing happens? any concerns with that?

thanks!

[timsrv]

Yeah, that's probably the next thing to do. Have you put the meter between the battery and the van cable to see what kind of draw there is on the battery while the van is at rest? I'm assuming there's nothing obvious like the sound of the starter still running after start-up and no sparks flying or bad noises...........right? Probably a good idea to check the fusible links too. Tim

[jbrush]

ok, one more check before i put in the new alt. i turned on the key and tested resistance (with battery and alternator disconnected) and there's a 40 ohm resistance. turns out removing the "IGN" ignition fuse changes the resistance to 370 ohms.

now, my thinking is that this 40 ohms (equiv to .3 amps at 12 volts) is from something in the ignition that's supposed to be there. the key isn't actually on the "crank" position, so it's probably not the starter, but could this still be normal? or is this a sign of a short in the ignition?

ah well, i'm learning slowly about the basics of auto electrical!

[foreverly]

Unless you have a wiring diagram that has the resistance of every component listed you won't really be getting anywhere with that method.

400 Ohms is very little resistance. There is going to be resistance in the wiring to the battery & any components in the path. If you really have a short you'd probably be blowing fuses, something would burn up, or you'd having funny electrical issues.

But honestly, if you leave your battery connected to your van for two months without starting it - its not a surprise that some of the voltage has drained in the battery. That's normal for a complete circuit. Your cell phone & computer will do the same thing.

However, if you are sure that there is major current draw with the ignition turned to off then you are going to have to break the circuit & measure amperage in series with your meter as Tim suggested. Eliminating parts of the circuit until you've found the culprit.

Chasing resistance isn't the way to do it...

One other thing though. I've noticed with my van that I need to be cognizant of making sure that the ignition is turned to the Off position & not the position just before Off as my key will slide out in every position. Did you possibly have your key in the wrong position with the radio on & the volume turned down? Or leave the lights on? Did you leave the door open so the lights drained the battery?

I've also read that sometimes the switch on the door breaks & never turns off the interior light. Have you checked your switches?

[jbrush]

thanks, foreverly! appreciate the feedback, and i've been checking actual amp draw based on your and tim's suggestion. more on that in a sec.

first, a bit of clarification. this is *not* the traditional electrical issue where a battery sitting for a while with the vehicle off (a day, a week, etc.) gets killed by parasitic drain. the problem showed up with a completely new battery, while vehicle was running.

specifically, i put a brand-new battery in the vehicle, and started it just fine. after about five minutes of operation, the van cut out and wouldn't turn over at all. i tested it, and it was down to about 11.5 volts. in five minutes, while it was running!

if my calcs are right, that means something on the order of 700 amps of draw during that five minutes! so it's not a catastrophic direct short with sparks everywhere, but still something pretty major.

the situation now: new alternator plugged in, testing ignition sequence to figure out if there's something bizarre going on, before cranking it and potentially refrying the battery (or alt?). multimeter in series between ground wire and neg post of battery. key off: 14 milliamps. key accessories: 70 milliamps. key on (not cranking): 2.5 amps.

2.5 amps seems like a lot, but it could be that it draws that much through the spark plugs or something? anyone have experience with what the expected draw is with the key on, but not running?

thanks, all.

[foreverly]

jbrush - i'm not a mechanic & really don't know too much about the toyota vans other than what i've experienced in the last few months & what I've been able to devour between this site & tvp. but i did study electronics for a few years when i was younger.

Your measurements are interesting. You do have a parasitic drain of 14ma. But that doesn't sound too bad.

Also, you really need to be careful breaking the circuit when the key is turned to On & that much juice is flowing. You could hurt yourself or your vehicle. I'm not familiar with the spot that you are measuring but if its tight its possible that the high voltage potential could cause an arc.

I remember reading that the alternators on these vans can easily be damaged just from arcing the jumpstart cables. So be careful there too.

By the way, you mentioned that your new alternator had less resistance than your old one. That's a good sign that shows there may have been a problem with your old alt. Maybe not too - I don't know what the resistance is suppose to measure & both could fall within spec.

Unfortunately, I think the only way for you to see if your problem is fixed is to connect everything back up & give it a try. It sounds to me like you only experienced a classic alternator failure.

Cranking over your engine takes a lot of power so that combined with the slight parasitic drain may have been too much for your old ailing alt.

Good luck.

[timsrv]

Did you check the new battery voltage before you installed it? Keep in mind that new batteries are typically only charged to 80% before they are put on the shelf, then they sit for who knows how long. Based on what I've read so far, my guess is your old alternator is dead (pretty common on these vans). Then you put in a new battery that may have already been a little low. Starting the engine put around 150A draw on it, and then it had to carry the loads of ignition & possibly the fan motor or whatever. State of charge can be determined by voltage, but only after battery has been dormant for 24 hrs or longer. 11.5 volts measured during or immediately after loads were applied doesn't mean much.

Some other thoughts: Could it be that you had dirty, loose, corroded, or otherwise damaged battery terminal(s)? Unless the terminals are clean & tight it doesn't take much to prevent current from flowing. A loose, dirty, or otherwise damaged connection ANYWHERE between the battery and vehicle can do the same thing. So check condition of the entire length of all cables including where the + hooks up to the starter and the neg hooks up to the frame & motor mount area. look for corrosion between the terminal ends and the strands of copper wire too. Physically inspect all your fusible links. If anything looks burned or damaged, repair or replace. If all this looks good then charge your battery and have it load tested (it's rare, but new batteries can have internal problems too).

If you measured any less than 13v at the battery while the vehicle was running, then there's a charging problem (more often then not it's the alternator). If you need further convincing, take it out and have it tested at an auto electric shop. For that matter take your new one down before installation and have it tested too. Most shops will test for free. Even auto parts stores will test these, but there's often a question to the competency of the counter person (some of these guys will BS you rather than admit they don't know what they're doing). Last but not least, these alternator harnesses are also known to become damaged. Make sure there's no bare wires exposed anywhere. Another thing that happens is the small wires can break inside the insulation. These can often pass a visual inspection but still not conduct electricity. Tim

PS: Your amp draw readings you mentioned above are normal.

[jbrush]

thanks for the helpful info! well, a couple days ago i went ahead and attached the new alt. and checked all the cables, and tried to start. *click* i thought it might be the battery had drained, and recharged it, and tried again. *click* i borrowed another car and attached jumper cables, with 14.5 volts. *click*

by *click* i mean that there's a metallic sound in the middle/back (?) of the engine, which makes me think "solenoid", and the dash lights dim, but not the slightest sound of starter turning over.

this is very strange to me, because (if you recall) the last time i tried to start the vehicle it started fine, but then cut out after 5 minutes and wouldn't start again. that was a while ago, and i've disattached the battery, the alternator, the three wires at the positive bat. terminal, and the two wires at the pos. terminal in the engine. but i've reattached them all, no visible fraying, no obvious probs with the fusible link.

any ideas? does it sound like the starter is fried (or the coil, or something), or are there other (easier?) things i should check?

and on, and on, and on...
.brush

[foreverly]

You are going to have to do some basic investigating & troubleshooting. Its probably an electricity issue though so start there.

Do your headlights light up? Can you turn the radio on? Does the blower work? Essentially you need to find out of you have a good connection to your battery.

Read the fusible links thread & check yours fuses, & fusible links, etc.

Verify wiring to the starter.. tap the starter if you don't think its engaging.

One other think I want to mention is that while I love the information on this site & TVP the search features pretty much bite it. Use google instead with the 'site' command. So try something like : 'No Start site:toyotavantech.com' via google.

[jbrush]

thanks for the tips, again. searching via google i found the following ignition thread: http://www.toyotavantech.com/forum/s...witch-question

so i did the basic test for voltage under cranking at the starter. disconnecting the little wire, i test it at just under 12V on crank (and no solenoid click, i think). so that's fine. at rest, the big exposed nut is at 12.6V, as expected. under cranking, however, it goes down to 0.5V! i tried it again with another (running) vehicle connected by jumper cable and the same behavior -- goes down from 14.5V to 0.5V.

what can this be? seems like a short of some kind? or is it some kind of loose connection?

in the thread above it's recommended to trace along the ignition circuit. but if i'm understanding correctly, the fact i get 11.8V or so on crank at the little wire means the ignition circuit is ok. plus the fact that the positive terminal on the starter changes (to 0.5V) means that it's activating the starter. so the problem is between the starter and the battery on the heavy-duty wire? is that a correct interpretation?

fwiw, the voltage at the pos. post in the engine compartment goes from 12.6V to about 11.9V or so under crank, which seems normal.