Alternator issues....

[bajananyone?]

Me and my brother have just acquired a 69 baja for his first car. The engine runs absolutely great, however we seem to be having alternator issues. Its a Bosch al28n. Whenever we turn the headlights on the car runs for about 5 seconds then dies. The battery was 6 years old so I just assumed the battery wasnt taking a charge, so I went out a bought a new battery. We put the new battery in and the volt gauge showed 12 volts but we turned the lights on and the gauge showed 10 and slowly goes down from there. Im guessing that the alternator is bad because i checked all the connections and cleaned the terminals and it wont charge the battery at all. Should i just buy a new alternator? Help! I only have 2 weeks before i go back to texas and leave my brother and the bug here.

[Chris V]

Before you go spending a couple hundred bucks on a new alternator...you should try measuring the output at the B+ terminal.

How was the original `69 generator regulator under the backseat removed?

[Marc]

I assume you mean it's an AL82N.
Since a `69 came with a generator, there are some minor wiring modifications necessary in order to run an alternator. For an externally-regulated alternator it's quite simple. Note that alternators receive their initial "field flash" from ignition power feeding through the warning light filament back to the D+ terminal, so if the warning light circuit isn't right there will be no charging.
http://www.nls.net/mp/volks/schem/gen_alt.htm

[bajananyone?]

I made sure all the wiring was correct. I have the B+ wire connected to the positive terminal on the battery. The d+ is ran to an idiot light on the dash with a power source coming in to the other side of the light. It's an internal regulated alternator if I'm correct.

[Ol'fogasaurus]

Its been a while but try this.

Voltage check:

Using a volt/OHM meter, do a voltage check at the battery and mark down the reading (it should be slightly higher than 12 volts. I the engine has been run before the battery test has been started, the reading may be as high as 12.8 volts.

Next start the car and do another check; when the engine is running you should get somewhere around 13.8 to 14+ volts. Turn on the lights and see what happens.

Amperage check:

Turing on the key, the amp needle should slightly drop below 0; when the starter is engaged and during cranking the negative draw will be more. When the engine starts and the charging starts to function, the needle should go into the positive when the engine is running and show the amount of amperage that the generator (~30 amps) or alternator (~55 amps) output is when it starts to make electricity and replace the charge removed from the battery when starting the car. This should take a couple of minutes normally before the needle comes down to just above 0 indicating that the re-charging of the battery is complete. If the charge stops too soon, you could have low battery fluid in the battery or a sulfated battery and the battery is only taking a surface charge (there are other things too like bad connections or bad cable. Check the ground connections before starting any of the tests. Ground cables are wicked, wicked things!).

On a running engine, if you turn on the lights there should be a jump in the needle, still in the positive but something less than the alt’s normal positive output (alt output minus light draw). Each time you put more draw on the electrical system the lower the amperage reading should be until you over draw the charging system then your gauge will show into the negative side.

If, when you turn on the lights the needle of the gauge slams to the bottom of the minus side of the gauge you have a full short; if it flickers from pos to neg then you have an intermittent short.

Anyway, a few of the things I remember to check.

Lee

[Marc]

If you have only one B+ wire at the alternator, it needs to be connected to two other large wires under the back seat - one going to the front of the car, the other to the battery positive terminal. The original voltage regulator is not used in any way.

It's also legit to use a second large wire from alternator B+ to the positive cable on the starter solenoid in order to get power to the battery.

There must be a complete current path for the battery to charge - I've seen problems caused by painted alternator housings and/or pedestals...

[Dale M.]

Functionally a Al 82 alternator needs to be wired this way...



And as MARC states all the large gauge red wire where regulator used to be must be connected common...

Dale

[bajananyone?]

I had everything wired correctly and I was trying multiple things to make it work but i finally gave up and took the alternator out to get it tested. It was bad. So we have a new one on the way and I hope to have it in by Friday. Thanks for all your help.