So i just got my car back together and something is up with my charging system. The battery was dead so i jumped it but the alternator didnt charge and keep it running, it died. So I checked with my multi meter and I get the same voltage readings from across the battery, alt cable post to chasis, and alt field plug to chasis. They all read the same dropping voltage as the battery dies, and if you remove the neg battery terminal the car dies. I figured it was the alt so i had it tested and the auto parts store said it was good, and output 14.7 volts on their machine. So what else can I check, I cleaned the terminals and the cable to the alternator, the only blown fuse i can find is the ac which I dont have. Does anyone have any ideas why a good alternator wouldn't be working properly? Are there any fuses im not seeing somewhere?

 

Ok, another question. On the field connector the blue wire rings out to positive, but the black wire does not ring out when grounding the multi meter to the chasis. Should this wire be grounded all the time or does a relay need to complete the circuit or something? Sorry im a bit un experienced at electrical.

 

Well, the next day the alternator started working again and now a couple weeks later its doing the same thing. Does anyone have any ideas?

 

you should not run your car with the battery disconnected.
14.7v off the alternator terminal is correct.
I'll say its most likely a bad battery or bad connection.
Does the car crank at all?
Read the voltage on the battery with the car not running.
Read the voltage on the battery with the car not running and lights on.

 

The car cranks and starts when the battery has power, then it runs untill the battery gets too low and dies. Multi-meter shows the same dropping voltage across the battery, alternator post, and from the alternator field connector to chasis, it never comes on. It did the exact same thing a couple weeks ago and then for no reason the alt started working perfectly again untill today when the same problem is back.

 

what your volts from the batt when the cars running? How old is the battery

 

11.4 or so and keeps dropping, its a pc680 so it drains real fast.

 

I think I finally found the problem. I decided to remove the whole starter/alternator harness and test all the wires and I found that the black wire from the alternator field connector wasn't ringing out to any of the connectors on the other end. I stripped off all the old brittle tape and wire looming and repaired the broken wire (it goes to the light grey connector with only 3 wires going to it next to the main fuse box) and re-wrapped the harness with some fresh stuff and it seems to be good now. I would guess that the initial problem fixing itself was due to the harness being twisted in just the right way to allow the broken wire to still make contact.

 

I was wondering if you re-wiring your altenator fixed your charging issues permanately. I have a fc and replaced the alt, battery, and starter. I found I had a grounded wire from the battery to the amp so i replaced it and that fixed my charging problem(the problem was it would drain the battery when turned off, and not supply enough power to the car to power the amp when turned on) Now after rewiring everything it worked fine until yesterday i went to the liquor store and within 1 min my battery was completely dead. Im thinkin it is my alternator b/c if i disconnect my battery it holds a charge fine. also when i stopped at a light just before going to the liqour store my cd player and amp cut out, and continued to do so everytime i came to a complete stop.

just curious if my situation sounds similar to yours. thanks in advance for any feedback