Alternator wiring diagram?

Disconnect the alternator wiring harness and check for power at the light green and red wire do you have it? Below is your charging system wiring diagram.

Disconnect the one with the light green and red wire-you check at the harness end.

Possible alternator ready to fry up and bomb out on you.
If you have Advance Auto Parts near you. Have them check your alternator. They will check it at no cost.
Good Luck;
Rick

Hi sjpd1959,

Thank you for the donation.

You need to perform a test on the charging system to verify if it is a fault with the alternator.

A faulty ignition switch or power interruption can also cause the symptoms described.

Most likely the cluster or the dimmer for the cluster. Remove the dimmer and use a test light to see if the feed wire changes when you dim or brighten it, if nothing the dimmer may be bad, if it works but dash stays dim th ecluster may need to be repaired or replaced

We can't tell you what alternator you have on your car but I can tell you as far as the first 2 go, you should be able to just swap pulleys to correct any problem there.

Hi towny. Welcome to the forum. I think I can help you but I have to search for a service manual. Electrical is my specialty, and my sub-specialty is charging systems. Until I find a book, can you describe the generator? Does it have a rectangular plug on the side with two very fat black wires with orange stripes? Or does it have the voltage regulator bolted to the back with a white, yellow, and green / red wire?

Caradiodoc

Well, I found a book but the diagrams are really confusing. Can you tell me if your generator has an external fan on the front that you can push on with your thumb? Next, I think you have the 65 amp generator with the regulator bolted to the back. There's a three-wire plug on the regulator, with yellow / white, white / black, and light green / red wires.

If you have only a total of three wires, (black / orange, white / black, and orange / light blue), you have the 100 amp generator with an external voltage regulator. Since you have the more common dual black / orange wires, I'm using the 65 amp diagram.

Start by checking for voltage on the two black / orange wires. They should both have full battery voltage all the time. By the way. Those wires are never supposed to be unplugged because that will degrade the solid mechanical connection, and that will lead to overheating of the terminals and rapid failure. Replacement units come with a new plug already installed, and you are supposed to splice and solder the wires to the vehicle's harness. Weird, huh?

Next, the yellow / white wire in the regulator plug must also have battery voltage all the time. If it is missing, there is a fusible link attached to the starter relay. The wire has nothing in common with the starter circuit. It is just used as a convenient tie point. Of the six wires shown on that terminal, the fuse link is a gray 16 gauge wire. That is the weak link in the chain. The wire is smaller diameter than the main yellow / white wire so that's where it will burn open. The insulation is designed to not melt or burn. Test it by tugging on it. If it acts like a wire, it's ok. If it acts like a rubber band, it's burned open. You can buy replacement fuse link wire from the auto parts stores according to color. You can usually use less than half of the piece they give you so you'll have enough for another repair later.

Next, measure the voltage on the green / red wire. There should be 0 volts with the ignition switch off, less than about 1.5 volts with the switch on, (that terminal is grounding the dash light), and it should pop up to near battery voltage when the system is working. Battery voltage on both sides of the dash light turns it off.

Also, when the system is charging, there will be around 5 - 7 volts on the white / black wire. That voltage is tapped off the output and is what tells the voltage regulator to raise the voltage on the green / red wire to turn off the warning light.

Let me know what you find on those wires.

Caradiodoc

Check all the fusible links in picture one or all of them can be blown they will be on starter relay or where positive battery cable hooks up for check engine light, scan for codes. Get code get back to us with code. Connector is under hood.

Look for a blown blue 15 amp fuse. Next, measure the voltages on all of the wires while the engine is running, then holler back with those numbers.

Do you have wire colors to go with the voltages?

12.1 at the battery wire is correct. If there's 0 volts at the stator (white or white / black), that means there's no output. That tells the regulator to turn on the battery warning light. "A" is system voltage sensing and should be 12.1 volts. The field should be higher. The higher the voltage, the higher the current flow through the brushes and field winding. The higher the current flow, the bigger electromagnet it makes. The bigger the magnet, the more output current you'll get. With 0 volts on the field, there won't be any output generated.

When you measure these voltages, measure at the generator and at the regulator to be sure you have the same voltage on each end of each wire. If one has different voltages, look for a corroded wire or a loose terminal in a connector.