Voltage regulator

Hi and thanks for using 2CarPros. Com.

There is a fuse under the hood (left front fender) fuse number 31 and G. Take a look at the attached wiring schematic and let me know if it helps.

I will watch for your reply.

Take care,
Joe

I am here to save the day! First of all, it is good that you are using a test light instead of a voltmeter. For this type of tests, a voltmeter can give misleading results.

You already found 12 volts on the large output wire on the generator. Check for that on the smaller red wire in the plug too. It should be there all the time. That 12 volts comes through the 7.5 amp fuse, so if that is missing, look for a corroded connector terminal or a break in that wire.

Next, the yellow wire is the turn-on signal that tells the voltage regulator when to turn on and do its thing. That current comes through the warning light in the instrument cluster, so check if that bulb is working. If that bulb never lights up, check fuse 8, a 10-amp in the inside fuse box. Do not worry about the bulb itself. They almost always have a resistor in parallel with them to insure the regulator gets its start-up signal if the bulb has burned out.

The best way to test on the yellow wire is to back-probe it with the connector plugged in, but that is not always possible. If you were to use a voltmeter, expect to see around 2.0 volts with the ignition switch on. Ten volts is being dropped across the dash light so it is lit up, and that leaves that 2.0 volts you see at the plug. If you unplug the connector, and then measure on the yellow wire, you will find full battery voltage of 12.6 volts, and the bulb will be off.

If you do this with a test light with the connector unplugged, half of the battery voltage will be dropped across the dash light, and the other half will be dropped across the test light's bulb, so both will be dim.

If all these voltages are right, inspect the connector terminals to see if one is spread and not making good contact. With the engine running, often you will hear the engine load down a little and you will hear the generator start to labor if it starts working while you are wiggling the plug. You can also watch the brightness of the head lights change or you can use your voltmeter to measure battery voltage. When the system is working, battery voltage must be between 13.75 and 14.75 volts.

It is also part of the regulator's job to place full charging voltage back on the yellow wire when it sees the system is working properly. With, ... Lets say 14.2 volts on the yellow wire, and 14.2 volts at the battery, and therefore on the other side of the dash light, it has the same voltage on both sides so the dash bulb turns off.

I know you said you checked the ground, but to cover all the bases, some generators are mounted on rubber bushing to insulate them from engine vibration. Those need to have a large ground cable or braided ground strap connected between them and the engine. The cables often get removed for some other service, and then forgotten, and the braided cables often corrode and break.

Hold on. You said the red wire has 12 volts all the time. Is that what you really mean or did you mean it is supposed to have 12 volts all the time, but it does not? It should have 12 volts all the time. If that red wire is shorted to ground, the 7.5-amp fuse would be blowing. Please be sure I'm clear as to what you have.

The yellow wire gets 12 volts put on it by the voltage regulator when the generator is working. The easiest way to tell if that wire is okay is the "Battery" warning light on the dash will light up when you turn on the ignition switch.