Charging systume in a 90 Tona Shelby VNT...

[shelbyplaya]

ok so i got NO charge whats so ever coming from the alt. BUT i got it checked out and it's opering at 100%.

i've checked and re-checked the grounds and they all seem fine.

i'm gonna go swap in a new sub harness and see if that changes anything.
i've also swapped in a differnt VNT sbec and got the exsact same thing from it.


i dont know if it helps any but it's also giving me the code for the fan circuit


12 Memory Standby power recently lost
35 Problem in Fan Control Relay driver circuit
61 Baro Read Circuit Failure
64 VNT Solenoid # 1 Failure
41 Charging System excess or no alternator field current
65 VNT Solenoid # 2 Failure
25 Problem in AIS (Automatic Idle Speed) driver circuit
55 Indicates End of diagnostic codes


thank god for copy/paste




UPDATE:

Changed the alt. sub harness and no change.

the codes i'm getting from the car are:

[charger R/T]

well you got lots of codes but only asked about charging system. Thats probibly good because charging system issues can cause other codes. First we need to see what voltage it is not just its not charging. If the battery is 12.5v with engine off and drops from there when running yes it isn't charging. It its at 12.8 it not really charging correct but it is doing something.

With the engine off take a volt meter and check the voltage on the battery post on the back of the alternator (big stud near field wires) it should be the same as the battery. If its not you have an issue from there back to the battery. There usually a fuse link near the battery in that wire. If its burned you will get 0 volts at the alternator. If there is voltage just low high resistance in the line.

Also with the volt meter hook the ground terminal of the volt meter to the alternator case and the positive terminal to the positive battery cable to check the case ground. Again it should be the same as battery voltage.

If that is all good it on to the 2 field wires. These 2 wires basicly tell the alternator how much to charge. One of these wires gets a 12v+ when the engine is running. It usually won't read anything with the engine off because I think it gets it power from the fuel pump relay on some cars. So not run no voltage. I also believe this wire is the DG/OR wire.

The last wire is a DG wire. It goes to the computer and the computer gives it a ground to make it charge. Think of it this was the computer reads output voltage and if it is low the computer gives this wire a big ground. As the voltage comes up the computer will lower the ground. To sum it up big ground lots of charge little ground little charge. This is the hardest wire to tell people how to check it. There are a few ways to do it. I like to tell people I'm helping to remove this harness off the alternator. (disconnect the battery first because the battery feed needs to be removed too if the factory connector is still there) tape up the battery wire so it doesn't short out later with the battery hooked up. Hook up the battery and put your volt meter on the 2 field wires and start the car. The volt reading should be close to battery voltage because the alternator is not hooked up to charge and the computer will command it to charge alot. If the voltage is close to battery voltage you have an alternator issue. If it is not and the DG/OR wire did have the correct voltage when you checked it you either have an open wire (DG) from the alternator to the computer or the computer has an internal problem.

Hope this gets you started to fix this. If you need more info just post.
Tim

[shelbyplaya]

that battery dosent get any charge whats so ever, when the battery dies from the jump start the car does to.


but i'll have to buy a new volt meter today and test everything out.

[charger R/T]

If your jump starting it and removing the cables and it dies you need to start by charging the battery or getting one in there that will start the car on its own first before digging into the charging system. With a battery that low you are asking the charging system for too much and can't properly check things.
Tim

[shelbyplaya]

ok here's my findings

on a good test car EVERYTING read 13.85 +/- .1v
^i used it as a referince)

on the VNT...

battery WAS 12.00

big black wire = 12.00

2 smaller wires .16v ('lower') and .12v ('upper')
and the alt casing was 12.00

[charger R/T]

was the engine running when you tested the 2 small wires. One of those should have read 12 volt and the car has to be running to have the voltage there. It will not be there with just the key on. If the car was running it looks like you are missing the 12v+ feed to the field. It will not charge without it. I don't have a 90 FSM to see where that wire goes. But my 92 shows it comes from the ASD on a 92 but there are many wiring diferances between 90 and 92. You might do a search NAJ may have posted charging diagnois for a 90 for someone else.
Tim

[shelbyplaya]

i did it with the car running

[NAJ]

Charging and Speed control diagnostics are a totally seperate manual,I have 1 for a 92,have not been able to locate a 90 so i go back and fourth to be sure the wiring is the same.
90 and 92 AG body 2.2/2.5L are the same.Not sure about ASD relay control (DB/YL) at SBEC.(Term #51 on 1990)
Chrysler Fault Code #41 is open or shorted condition detected in alternator field circuit.
At Alternator ;
BK/GY wire is the 12 volt battery feed.(Unswitched voltage)
BK is an engine ground and is also the ground for the radiator fan motor.
DB is Switched ignition voltage thru fuse #16(15 amp).
Comes out of fuse box as DB/WT,runs to a splice where DB/WT runs to Rad Fan Relay, the diagnostic connector and is power for all underhood solenoids.
At the splice the DB/YL wire runs to an underhood connector where it becomes DB to the alternator.
The DB/YL is also the ASD relay control at SBEC cavity #51.
DG is the alternator field control to SBEC cavity #20
Do you own or have access to a scan tool so you can activate the field control circuit.

[shelbyplaya]

Quote:

Originally Posted by NAJ Charging and Speed control diagnostics are a totally seperate manual,I have 1 for a 92,have not been able to locate a 90 so i go back and fourth to be sure the wiring is the same. 90 and 92 AG body 2.2/2.5L are the same.Not sure about ASD relay control (DB/YL) at SBEC.(Term #51 on 1990) Chrysler Fault Code #41 is open or shorted condition detected in alternator field circuit. At Alternator ; BK/GY wire is the 12 volt battery feed.(Unswitched voltage) BK is an engine ground and is also the ground for the radiator fan motor. DB is Switched ignition voltage thru fuse #16(15 amp). Comes out of fuse box as DB/WT,runs to a splice where DB/WT runs to Rad Fan Relay, the diagnostic connector and is power for all underhood solenoids. At the splice the DB/YL wire runs to an underhood connector where it becomes DB to the alternator. The DB/YL is also the ASD relay control at SBEC cavity #51. DG is the alternator field control to SBEC cavity #20 Do you own or have access to a scan tool so you can activate the field control circuit.

thanks.

no i do not have access to a scan tool

[NAJ]

Start by checking the 2 power wires and the BK ground wire to eliminate those as a problem If you have unswitched power,switched power and external ground all that is left is the field control circuit and we can focus on that.