yotajakes

so the truck is an 89 pickup, manual 22re. ive been chasing this problem for awhile now and for the life of me I cant seem to figure out what the reason.
so I got a parasitic drain that is killing my battery in a few days unless I drive the truck everyday. two days of sitting and its dead. the drain is in my alternator system itself.

now for starters so you know where im at, new parts, optima red top battery that's at 12.4 volts prior to testing, 3 ( yes this is the third) new alternators.(I couldn't necessarily say they were bad after the first one but I always come down to the diode being bad), checked all the wiring from the battery to the fuse box to the alternator. all grounds are present, connections new and clean( been checked dozens of times).

so heres the full problem, alternator system is pulling power when truck is off. right around 120 ma. so starting with the ammeter, hook it up to the battery, show 120 ma draw, pull the 40 amp am1 fuse it drops to .01 amps. initially I figured that it was just the alternator so I changed it. its been in for several years, time to change. so new alternator, few days go by and dead again, so old battery goes away and new optima in. still got a power draw. 40 ma this time. so not as bad but enough to kill the battery. check the whole wire harness out, everything looks good, replaced most just to eliminate the possibility.

so a couple months of research and troubleshooting and still at square one. so I decide to start cutting wires and seeing what exactly happens. all the wires running to the alternator. so if I cut the main white wire going to the post it drops down from 40 to 3 ma. hooked back up, now I cut the small white wire going to the plug on the alternator, it drops to zero... with the big white post wire that had the drain from the previous sentence hooked up/not cut. now this Is where im unable to figure out where to go from here.. tracing the white plug wire from the alternator back to the battery, it goes to the am1 40 amp fuse, to the 80a fusible, to the battery. the large white post wire to the fusible 80 amp to the battery. also if I leave the alternator hooked up to wires but unbolt it from engine, the drop goes away. so I know the drain is flowing through the alternator itself and not a wire in the harness. all this still says to me that I have a bad/blown diode in the alternator, but this is the third alternator.

furthermore to dispute the bad diode theory, Ive done the quick diode check with the multimeter on all the alternators. set meter to diode check, touch main post and housing of alt. take reading and switch leads. should have a high reading one way and no reading the other for a good check. all checked good out of truck and not hooked up to wires, but with them hooked up to wires they failed.

so this leads to my main questions/ mind boggling.. what controls the alternator flow of electricity? what turns it on and says flow power through you to the battery?

I need theory of operation and specifics.

sorry if this comes out as a little jumbled, I have been checking, rechecking, researching and troubleshooting this issue for about 6 months now. and it frankly has my brain fried.

ready set GO!!!!!!

RAD4Runner

Looks like the thin white wire is giving you the most significant drain. Did you physically trace and inspect it to make sure it does not have worn out insulation that causes short to ground?
If you physically trace it, you would see that it taps of the thick "B" wire near the fuse block.

How the charging system works and recommended test points.
https://www.yotatech.com/forums/f199...l#post52094780

yotajakes

I have physically traced the whole harness from fuse box to the alternator and battery, back and forth multiple times.

Cutting the small white wire to the alternator plug kills all the power drain. Every bit of it. Now with it hooked up, if I cut the main post large white wire, all but 3 ma is removed from the drain. Re-cut the small white in conjunction with the large and it goes to 0. This is where I'm confused. It's almost the same power draw but with two wires, and whatever the small white is designated for is the main culprit in allowing the drain to flow through the large white. My reason in thinking this is that with the small white cut and only the small white, the drain is completely eliminated.

osv

i had a slow drain on my '86, that was due to not turning the key all the way to the lock position, while holding the button on the column down... battery would drain in just a few days.

yotajakes

I've got a new lock cylinder and a new ignition switch. The only component pulling power is the through alternator. Thanks for the input though.

I'll go through the thread posted above and check out all the checks listed and see where that leads me. Any other input anyone has thank you in advance.

wyoming9

iTrader: (1)

Sounds to me like a shorted diode not to be confused with a open diode

yotajakes

This is the conclusion that I always come to. There is a test you can do to check the diodes in the alternator, with the alternator unhooked from wires or out of the truck it passes this test, in the truck hooked up to wires it fails. All 3 of the new alternators tested similiar. I've got new parts that were bad out of the box but 3 in a row? I may have to just tear the alternator apart and physically check the diodes.

Main main thought on this though is why does it pass the external check unhooked then fail when it's hooked up? What is telling the alternator to flow energy, or allowing it to do so?

I may be over thinking this, but all the simple areas such as bad grounds, broken or damaged wires/shorts, bad diodes have been checked multiple times and components replaced..

Again great input, I wish some of you guys were local and could come check it out. I've never had such a hard time diagnosing a problem before.

atcfixer

iTrader: (1)

I'm looking at a service manual for an 94 pickup and it looks like there are a few components that could be related but it does seem to point at alt based on the other reference link.

Might want to watch the load, and try unplugging the Ignition switch and starter relay to see if it makes any difference. The load is quite low, I don't remember what is allowable for ecu memory and radio. I know the 120ma is way too much, but the 40ma is getting closer to acceptable.

yotajakes

I'll give that a try and see if that makes any difference. Ya the 120 ma would kill the old battery quick. The 40ma is still eating battery life away pretty good. From the research of various vehicles and systems, under 25ma is good but under 10ma is optimal. I have pulled just about every relay and fuse that has anything to do the alternator via the 89-90 22re wiring diagram. Even the heater relay. I'll disconnect the ignition switch and see if there is any change. Just waiting on the battery to charge back up.

Flash319

The alternator is supplied power to the field from the ignition turing on. Without this power to the field you do not generate power. The rotor field winding need a ground, thats why when you hold it in your hand the field goes away and you have no drain. I cant remember if the plug has a ground or if the body of the alternator is the ground.

The diodes on the stator only flow in one direction through the stator winding so you should have no flow to ground when the rotor is not turning. I dont have a wiring diagram in front of me but check that the power supply wire to the alternator is shutting off with the key. It is one of the wires in the plug.

Also a 120ma is not much draw. A new battery can supply that for a long time, like 20 days or so to kill. Sounds like a junk battery to me.

atcfixer

iTrader: (1)

You could do the test based on resistance too, just the numbers would be more meaningless since it takes match to convert the resistance numbers to what the ma load would be and we're missing the voltage level from the meter to do the math. It could just show if there is a change or not unless I'm thinking wrong.

I agree with flash, almost forgot here is the kind of a wire diagram even though it isn't very detailed. AM1 fuse also supplies power to the ignition switch and the 80a alt fuse for the starter relay, which is why I mentioned them.

https://gyazo.com/677290f72e272a8710a9072bdf494784

yotajakes

The plug doesn't have a ground. It grounds through the alternator. The harness running to the alternator has a ground wire that hooks up to the ps pump bracket and to the fender on the driver side. According to my diagram, the wire supply power should be the red ig wire. Yes?

yotajakes

I'll chase down the ignition switch Avenue and see what results that yields. Also, I'll do the resistance and voltage checks mentioned earlier and post up what I find.

Thanks again fellas.

Flash319

Looks like the Red wire is you ignition switch wire that prob runs to the AM1.

yotajakes

So quick comment on the idea of say the red wire is constantly supplying power even when key is off. If that were the case, if I disconnect/cut said red wire, wouldn't that stop the power drain? I have already clipped that wire before in prior troubleshooting and the drain remained unchanged. I'll give it another try, or try it in a different way.

Flash319

If you pull the plug you should have no draw on the alternator. If you do then your diode in the alternator is ng.
stick a meter on the red wire and check for switched 12v with the key on/off.

yotajakes

Well pulling the plug essentially does stop all the draw. But that is also disconnecting the small white wire that I previously mentioned. That's why I decided to individually cut each wire and see what the result was. Red and yellow had no effect once cut. Only the large and small white wire made any change to power draw when cut.

osv

you've replaced the alternator, right? worst case you can have it load-tested.

what i'm talking about probably isn't related to the condition of the ignition switch, it's more like how the truck is wired, or possibly mis-wired, and turning the key to the lock position has eliminated the issue in a number of these trucks... terry posted about the key position, also see the second post here: https://www.yotatech.com/forums/f116...-drain-281829/

pull fuses to troubleshoot, don't cut wires, because it can introduce other problems.

yotajakes

That introduces a whole bunch of looking for me to do. Never thought about checking for hack jobs under the dash. The engine bay harness is good order. I'll inspect the rest.

Also the only reason I cut the wires was to facilitate changing some bad sections out, but figured I may as well see what each wire cut did. Each cut connection was soldered back together with new wire and marine shrink wrap.

osv

turning the key to the "lock" position is a pretty simple troubleshooting step.

good job on the repair... now wrap the shrink with some of that self-fusing electrical tape.

here is more troubleshooting steps, i think that it did end up being a bad alternator in his case: https://www.yotatech.com/forums/f131...77/index2.html