79 battery STIIL not getting charge

[bmwbeemer7]

I am having the hardest time with this 79 928 not charging the battery. Can I just run a wire right off the alternator straight to the battery for charge. I am just so sick of working on that car trying to figure out the problem. I have a brand new alternator. I have tried everything. I am just to the point of running a wire directly to the battery from the alternator. All I need to know is CAN I DO THAT??? Thanks!!

[neil30076]

Before you do that -
With the ignition off - use a digital voltmeter - put the black wire from the voltmeter on the - post at the battery -NOT to the frame of the car, and the other ( red) wire ( you will need to extend it) on the V+ post of the alternator itself.
If you get a reading of around 12 volts then you have a connection between the alternator and the battery. Compare this to the voltage directly across the battery, what is the difference?
Start the car, what do these voltages read now?

[bmwbeemer7]

Ok. I'll try that right now and let you know.

[bmwbeemer7]

The voltage with the car off was 12.53v. Then when I cranked it, it went to 12.09v. Weird. Any suggestions. i just don't get it.

[bmwbeemer7]

At the battery when the car is running, it read 12.31. And 12.53 when the car is off.

[neil30076]

Originally Posted by bmwbeemer7

The voltage with the car off was 12.53v. Then when I cranked it, it went to 12.09v. Weird. Any suggestions. i just don't get it.

That is not unusual - the voltage drop is due to the high current draw on the battery by the starter.

[neil30076]

Originally Posted by bmwbeemer7

At the battery when the car is running, it read 12.31. And 12.53 when the car is off.

The battery voltage will creep up aftert starting, but this does tell me your alternator is probably not putting out anything ! I did not follow your previous posts, what is the story with the infamous blue wire!
Also, what is the voltage from the D+ ( blue wire) to frame when the car is running?
Per teh factory -
Regulating voltage
Connect voltmeter to D+ and ground (earth).
Switch on ignition: = 1.4 - 2.0 Volt
Start engine. = 13.2 - 14.2 Volt

[bmwbeemer7]

I was having problems before with the blue wire. It was charging the alternator for a few weeks but I put an alarm on the car yesterday and now I'm having this problem. I just checked the blue wire and it is dead. Even with the ignition turn on but not cranked. It still read 0. I just put that alternator on the car about 2 months ago. I bought it from Autozone.

[neil30076]

Originally Posted by bmwbeemer7

I was having problems before with the blue wire. It was charging the alternator for a few weeks but I put an alarm on the car yesterday and now I'm having this problem. I just checked the blue wire and it is dead. Even with the ignition turn on but not cranked. It still read 0. I just put that alternator on the car about 2 months ago. I bought it from Autozone.

The blue wire gets its voltage from a circuit that comprises the charge indicator lamp, and a resistor in parallel.
If the lamp is out, or the resistor is missing you would still get some voltage , but not enough to excite the alternator. So, to get no volts, the circuit is open. This circuit goes through many connectors to get to the alternator. One way to prove the alternator is good is to bypass all these connectors, The lamp circuit is between 2R (BLUE) and 1R (BLACK) on the right console connector. If you pull that connector ( no need to pull the console, only the plug on the right connector) you should see ( with ignition on ) +12 volts at the loose plug end on 1. With ignition off, If you check the continuity from 2 to D+ you should see a continous circuit.
Let me know what you find.

Neil

PM me and i'll send you my phone number, easier than multiple messages!

[JhwShark]

Try undoing the alarm and see if the problem persists??

Put some load (lights, fan, AC) on the Alt when started and give us a v reading.

If so, then maybe bad diodes in Alt. IS the AZn a rebuilt or new and what make??

Or, wires in the harness from the 14 Pin or the 14 pin...I am not sure if you are the poster who had elect issues lately??? Please let us know what else you have been adding into the beast...

[Mrmerlin]

we need to know where your measuring the blue wire from??
It also goes through the 14 pin connector above the hot post in the engine compartment ,
since your car is older there is a possibility that you have shedding insulation or corroded pins.
Try measuring the 12v feed at the 14 pin connector.
It should be pin #1,
with the key on if you have voltage there then there is a good chance the blue wire has been damaged between the 14 pin and the alternator,
usually from hanging the alternator from the wires,
the wire will usually shear about 4 inches up the harness from the alternator.

With the engine running you want to see 13.5v or higher at the hot post.
Also make sure the starter wires are clean and the grounds are all good ,
To include cleaning the battery terminals and the ground wire connection to the chassis ,
and the ground wire at the block to chassis under the right exhaust manifold. clean the hot post connections and the 14 pin connector as well

[neil30076]

Here is your circuit for a 79.

[bmwbeemer7]

I checked pin 1 at the hotpost and it read nothing. I unhooked the alarm and still no difference. Pin 1 read 0 not matter what I do.

[JhwShark]

I am sure you are frustrated...please be very clear with the details.

Give a summary list of voltage readings: OFF, ACC/ON, Running:

Hot/jump post
14 Pin connector @ Pin #1
ALT D+
ALT B+

[neil30076]

Originally Posted by neil30076

Here is your circuit for a 79.

In this diagram, the pin 1 that Stan refers to is T14/1, just above the D+. As you can see, if you go to the CEL you can follow that path through O8, Z1, Z6, H8, to the console.
So, start at H8, with ignition ON, do you have 12v, then follow it all the way back up this path asnd see where it is missing.

[Landseer]

Exactly. Trace it back. Nice diagram.

[bmwbeemer7]

Ok. here is what I got so far.

Ignition off
Pin 1 o.5v
Hotpost 12.88v
D+ .5v
B+ 12.69

Key on
Pin 1 1v
Hotpost 12.22v
D+ 1.2v
B +12.25v

I am still testing so I'll post more results today. Also, do you think maybe the circuit on the battery gauge may be blown causing my problem? I did notice one thing when I first started to install the alarm. When I went to remove the glove box at first the light worked and then it blew when it touched metal(my accident). The wires leading up to it are red and brown/white. Now the red wire read nothing. The brown/white is a ground and it is good. But the red did obviously go dead when it hit that metal. Also, is it hard to remove the instument panel to get to the circuit behind it? Thanks sooo much guys for all the help too!! James

[Landseer]

The glove box light shorted and blew a fuse. It won't affect the charging circuit.

Does the snippet of wiring diagram clarify for you how to trace the circuit?

Can you say more about this statement: "when I first started to install the alarm" ?

What other wiring diagrams do you have for this car?

Where are you located?

[Mrmerlin]

I hope that your measuring the car side of the harness not the engine side at the 14 pin connector.
Since your having problems with elex system take a close look at the connectors along the bottom of the CE panel look carefully to see if any of the individual female connectors are pushed out of the plastic connector housings.
Take a picture of the CE panel and post it.
.
With the Battery removed drop the CE panel and inspect the rear side for melted wires.


Take the alarm you bought,
remove from the car and give it away. it will do you no good for the 928

[bmwbeemer7]

I am in Columbia SC. I unhooked the alarm yesterday as soon as I saw I was having a problem. Where is the car side of the harness? I was measuring at the 14pin on the passenger side of the car just above the hot post. Should I be somewhere else? I'll go through the wiring diagram today and let you know what I come up with.