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Freshly rebuilt alternator and tested good, new fully charged battery, no blown fuses. It refuses to charge. I have checked the ground cable resistance from terminal to body and alternator mount. Less than 1 ohm on both. Same for positive cable to fuse and fuse to alternator. All 3 terminals on the alternator plug show proper voltage when they should. I am at a loss.
It all started a few months ago when my alternator started getting weak. It would charge enough to not let the dash light come on but not enough to charge the battery. Voltage at max would be 12.1v. Also front bearing was going out. So I took it off to get it rebuilt. Got it back this week and put a new battery in at the same time because it was weak also. I have pulled the alternator off no less than 6 times. Took it to get tested just incase and it shows outputting 14.9v on average. I was thinking maybe the 3 pin plug but I tested it up to around the valve cover and all 3 wires tested fine to the plug pins. Anyone have any ideas before I go crazy?
I found a diagram that looks right. Seems as though the IG and ALT-S use 12v (battery voltage) and the L goes to the ECU for the dummy light. So for testing purposes could I not just take the IG and ALT-S wire and wire straight to the battery to see if it will charge? What about the L terminal?
Lets try dumbing it down a little and start with the basics LoL (unless you already have) I'm all about the technical like this and its fun, but need to start with mechanical. Question, hows the tension on the belt? Is it slipping? Did you swap the belt when you replaced the alternator? Is the tension too tight or too soft. Lastly and most importantly. Check ALL the grounds, its possible one or more has broken, check the ground going to the block. I wouldnt be surprised if its a ground problem.
I cant remember if our alt's are internally regulated (I don't think they are), if that's the case, worst case scenario is the voltage regulator in the ecu has gone kaput!
The belt is nearly new. Almost no wear. The tension is within spec also. The only ground I see is the main one from the battery. It has a connection on the frame rail beside the alternator and then goes to the bottom bolt of the alternator. Well those and the small one from the engine to the firewall. All test good.
As for the voltage regulator, I thought ours was internally regulated. Or is that what the wire to the ECU does? I was a mechanic at a previous point of my life but charging issues was my least favorite thing to troubleshoot. I would rather do a engine swap on a mid 90's ford Taurus SHO than deal with charging issues.
Do we know what the voltage from. The ECU wire to the alternator should be? That may be my issue.
Unfortunately I didn't have $200 for a Denso rebuilt one but my local shop rebuilt it for a little less than half. He has rebuilt my alternators for at least 15 years and is very reputable here in Mississippi. I have had the alternator tested and it passed with flying colors. I don't think it's the alternator itself but rather the plug or wiring. Maybe the terminals in the plug not making contact with the terminal in the alternator?
Unfortunately I didn't have $200 for a Denso rebuilt one but my local shop rebuilt it for a little less than half. He has rebuilt my alternators for at least 15 years and is very reputable here in Mississippi. I have had the alternator tested and it passed with flying colors. I don't think it's the alternator itself but rather the plug or wiring. Maybe the terminals in the plug not making contact with the terminal in the alternator?
I have a chepo Bluetooth code reader and the Fusion OBD app on my phone. It shows voltage straight from the ECU. If you have access to something like that I would check there to see if the vehicle ECU is getting the same power from the alternator that you are getting when it's bench tested
I have a chepo Bluetooth code reader and the Fusion OBD app on my phone. It shows voltage straight from the ECU. If you have access to something like that I would check there to see if the vehicle ECU is getting the same power from the alternator that you are getting when it's bench tested
Yeah I have an elm327 compatible adapter also and torque app (android). It has always read lower at the obd2 plug than at the battery since we have had the car (a little over a year now). But then again so does my sienna and my previous IS300. So I just chalk that up to a cheap obd2 adapter.
Maybe I'm confused why the talk of getting another alternator when you've already got yours tested as fine? This is why it leads me to believe its something simple as a ground.
Maybe I'm confused why the talk of getting another alternator when you've already got yours tested as fine? This is why it leads me to believe its something simple as a ground.
Sorry if I was confusing. I had my alternator rebuilt. It had a bad front bearing and a few bits inside was going bad. It tests 100% now. I will test a few things like running more grounds even if temporary to test stuff. I'm beginning to think it may be something with the wire to the ECU but again, I hate charging issues.
take your volt meter and set it to ohms. than disconnect the alternator connector and find the wire that goes to the ecm and which connector that is. than unplug it than do a continuity test from the alt. plug to the ecm. plug. that will atleast verify if the circuit is good. its called the voltage sense wire. you'll have to get a wiring diagram, im sure jokster would be happy to post one up here.
So after some research... The alternator is internally regulated, so I dont see any control by the ecu. I still say a ground issue... But now that I sit down and actually think about it, I completely forgot to mention fusible links. Being that it stays running at 11-12v says that its running completely off the battery. I dont think the alternator has any power coming out of it at all, well past the link that is. All the wire checking you did was only showing voltage that the battery was still linked to. I would bet that if you pulled the terminal off the battery while its running, it would shut off since nothing is coming from the alternator.
07-14-16, 02:32 PM
99 GS400 not charging
why the talk of getting another alternator when you've already got yours tested as fine? This is why it leads me to believe its something simple as a ground.
