I'm kinda new to this forum still so if I am doing anything wrong please feel free to let me know.

I have a 87' TII with a charging system Issue.

Batter will not charge. KOEO the voltage at the Batt is 12.6v - 12.8v.

KOER starts up fine and starts at 13.6v.
After a few seconds you will start to see the voltage start creeping down about
.01v every ten seconds, until its KOER at like 11.5v.

I have replaced the Battery and Alternator and that did nothing.
All that I see besides those on my wiring diagram is a alternator relay that is located in the ECU.

The only thing I can think of that could have ever gone wrong was last summer I added a dual alternator belt pull on. When removing I accidental grounded out the power wire on the alternator to the engine and popped the main fuse.
Could there be something else I cooked along the way?

I'm just lost and need pointers, Iv's searched the forms and cant really find anyone with the the exact same issue and I thought I would start here.

Thank you.

 

did you ground out the alternator before or after it was new?
..and what is KOER and KOEO?..Eieio..

 

Is the alternator an S4 alternator or an S5? If it's an S4 it would have a plug in the back that has two wires. The Black/White wire should have 12 volts w/key to on and engine off and also w/the car running as well. The White/Black wire would have very little voltage w/key to on and engine off but has battery voltage w/the engine running. The plug needs to be coonected to the alternator when checking. You can stick a paper clip into the back of the plug wires for voltage reading purposes or ***** the wire with a pin to take a voltage reading from.

An S5 alternator would have two wires on the back but the wire that is not White/Black would have constant voltage w/no key in the ignition because it would be connected to the Engine fuse box thus it would receive constant voltage as opposed to voltage w/key to on.

 

rubbish/ corroded ground somewhere ?

 

you may want to trace all the wiring to make sure none of it burned up, it is possible to happen before a fuse blows for some exposed wiring to burn up and fuse to something.

 

 

Check all of the fuses, even the trivial ones.

Pull the alternator, take to autozone/napa/whatever and have them test it. It's free.

If it checks out, then start the wire-hunting game.

 

Took some more readings today and found some odd things.
I have 12v Black/White KOEO and KOER.
I have about 1v coming off White/Black.

But the odd thing is i will start it up and it will charge fine for the first 5-10 min at 14.2v then my idle drops and its starts falling on its face again.

I'm super lost and about to rewire the whole thing.

Any other suggestions??

 

If the voltage output drops and you rev the engine to at least 4000 rpm or so does the output start to increase or does it stay low. If it starts to climb back to normal levels then the alternator is not being excited properly when it is falling. Reving the alternator self excites the alternator and causes it to output voltage to a normal level. The voltage on the W/B wire should be close to zero w/key to on but should then rise to 12 volts w/the engine running. When the W/B wire has very low voltage w/key to on and engine off it would cause the idiot lights to turn on. If the engine is running and this wire still has low voltage then it again would cause the idiot lights to illuminate.

AND is the alternator an S4 or S5 as they are to be wired differently?

 

It is a S4 alt.
The voltage output increase during increase in throttle.
I found that my idle is around 600rpm and its drops at this. But then I raise it to 800rpms and its jumps up and charges fine. Could this just be a idle issue??

 

I believe changing alternator pulleys causes the car to output more at higher rpms but at the lowest rpms it actually pulls down the voltage as this is the trade off depending on whether the pulley is an overdrive pulley or an underdrive one. You might want to bump up your idle speed to account for this or play w/the throttle when at a complete stop if the low voltage bothers you. Also, your idle should not be dropping below 750 rpm in a normal aspect as the BAC, which is used to control idle, should prevent this from occuring.

 

I looked up a few things for increasing idle speed and the BAC. Could I just clean the BAC or remove it? I do have block off plates. Idk if this would help me or harm my problem. I will fiddle with my idle tomorrow and see how she charges. Thank you for the help so far.

 

The BAC is there to prevent the idle from dropping below 750 rpm so removing it will not help you in any way shape or form. If your car has A/C then turn it on and disconnect the electrical plug to the BAC. The idle should drop noticeably. If it doesn't then the BAC is problematic for one reason or another.

 

I dont have A/C. Would it work with heat or no?

 

If you had the fan, lights and other accessories on it should be somewhat the same.