Why won't my car charge??? -- AKA: My Alt light never comes on!

[jluetjen]

OK, I've read a bunch of the old threads and maybe I'm missing something.

1. I've had the alternator checked and it checks out OK.
2. I've replaced the voltage regulator with a brand new one.
3. I've swapped the "alt bulb" with the high beam bulb. I also ohm'd it out and it was good and works great in the highbeam role. The highbeam bulb hasn't changed the charging problem.

The only other electrical problem is that the front right directional doesn't work. I've swapped/ohmed that bulb and it wasn't the problem. I took the bucket out to clean up the grounds. In the past I've already cleaned up the rear directional buckets which helped at that time -- about 18 months ago.

I guess I'll go out and clean the transmission ground and confirm the contacts of the battary ground cable.

Any other ideas?

[Rot 911]

Need more info. What is the voltage at the battery with the engine off? Should be around 12.5 volts. What is the voltage with the car running at 1000 rpms? Should be between 13.5-14.5 volts.

[jluetjen]

Hi Kurt, the voltage at the brand new battary is 13V, and the same or slightly less then then that when running at 3000 RPM. Based on a troubleshooting suggestion in my Chilton's manual (2nd source after my factory manuals) I tried measuring the voltage on the blue (Amp light) wire off of the voltage regulator with the ignition on and I didn't get any voltage. So now I'm in the process of getting to the alternator connection to the voltage regulator to ohm out that wire.

[IROC]

One thing to consider is that you need to check the voltage at the battery when there is a load on the system. My alternator was eating batteries about every 1.5 years, but checked out "normal" by most tests. It would put out about 14.5 volts at idle (seems OK, right?), but at 2000 rpm and with everything turned on I could muster (not much, really), it only put out about 13 volts. I replaced the alternator and it has been fine ever since.

HTH.

[Early_S_Man]

John,

There are two leads leaving the alternator warning lamp holder ... the Blue D+/61 lead, which goes to ground thru the slip rings and field winding, and the other side that goes to switched +12 Volts.

The +12 Volt side is fairly easy to verify with the ignition switch on.

The end-to-end continuity of the Blue D+/61 lead to ground with about 10 - 20 Ohms resistance can also be checked. If the Blue lead is open or has a high resistance connection, then it will take a bit of investigating to isolate the fault.

[jluetjen]

I figured out. To make a long story short, somewhere back in history someone connected the wrong two wires together. I figured this out after taking the idea from the Chilton's manual, and drawing out the circuit in question.



I then started ohming out the wires and checking voltages. First from the alternator to the Voltage regulator, and then from blue-yellow wires behind the dash back through the bulb. Then I took a 6 foot long stretch of known good wire to jumper my ohm-meter from bulb socket back to the voltage regulator.

Hmmm -- that's open. After searching around the electrical panal in the back left of the car, I found a blue wire that was orphaned. So I disconnected the blue wire out of the voltage regulator from what it was connected to, and hooked it up to the orphan. Voila! The alternator light lit right up. After confirming that the extra wire had no voltage when the engine was running, I taped it off and put it out of the way.

I no longer have to worry about the car not starting!

Thanks everyone for your input or just being here. Sometimes I find it builds my confidence to know there are a bunch of folks here to use as a sounding board. It's kind of like knowing the safety net is there, even though I may never use it!

[Early_S_Man]

Congrats, John!

You just saved yourself about $500 at a shop ... and who knows what other circuits would have gotten messed up in the process!