alternator pain in my !!!
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!!!!!! |
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 |
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. |
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.
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Originally Posted by osv
(Post 52336426)
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.
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. |
Sounds to me like a shorted diode not to be confused with a open diode
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Originally Posted by wyoming9
(Post 52336437)
Sounds to me like a shorted diode not to be confused with a open diode
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. |
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. |
Originally Posted by atcfixer
(Post 52336443)
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. |
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. |
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 |
Originally Posted by Flash319
(Post 52336447)
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. Sounds like a junk battery to me. |
Originally Posted by atcfixer
(Post 52336449)
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 Thanks again fellas. |
Looks like the Red wire is you ignition switch wire that prob runs to the AM1.
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Originally Posted by Flash319
(Post 52336454)
Looks like the Red wire is you ignition switch wire that prob runs to the AM1.
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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. |
Originally Posted by Flash319
(Post 52336461)
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. |
Originally Posted by yotajakes
(Post 52336428)
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.
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. |
Originally Posted by osv
(Post 52336466)
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. 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. |
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 |
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