Chevy G20 1985 wiring (charging problem)

Low battery, faulty alternator or voltage regulator, loose ground wire, loose wires going to alternator, belt slipping on alternator pulley.

Does the battery light work when you switch the ignition on? This provides a live feed to the alternator via the ignition bulb, the rotor needs a live feed to start the charge process, if the bulb has blown it won't charge (thin wire connected to the IND on the alternator). To check for a power drain, disconnect the negative battery lead put a AMP meter in series, (DON'T TRY TO START, YOU WILL BLOW THE METER). If you get a reading above 0.05amps (clock) you have a drain, pull the fuses one at a time and watch for a drop in the meter reading. Hope this helps.

Is the battery ignition light coming on when you turn the key on. Wiring for an alternator is quite simple, the 60amp cable (thick wire) is a direct feed to the battery. The thin wire (normally blue) connected to the 'ing' terminal gets a live feed via the battery ignition light. if the bulb has blown or this wire is not connected, the alternator will not charge. If you can, use a 12v 5watt test light connected to the battery, start the engine and touch the 'ing' terminal. this should prove and energies the alternator to start charging.

Only needs two wires, run a 40 amp cable from the large terminal on the alternator marked +, direct to the positive terminal on the battery or to the battery supply feed to the starter (which ever is easier). Then run a wire from the terminal marked 'ind' to a 5watt bulb, other side of the bulb needs to be wired to an ignition live feed. That's makes it the charge indication light. You need to fit this light, without it the alternator will not charge!!!! Light will come on when you switch the ignition on, and go out when the engine is started. Put a volt meter across the battery, should get a reading of 13.5 to 14.5 volts with engine running. Good Luck.

Have you checked for battery power at the large alternator post, and power at the small wire with the key switch on ?

the thiree wires usually are, one large heavy dity main wire that takes the charge current, one charge indicator wire and an exiter wire, when a car starts discharging it is usually one of the diodes in the alternator failed, there are usually 6 of these(at least) andthey should be dead short one way and open the other way when they fail they can be lowish resistance both ways and this discharges the battery, it will still show about 14 volts and give out 5/6ths of its rated amps but will drain, the ignition light(or charge light) is just a bulb from live to one diode and unless it is that diode that failed the lamp will work fine.The way to check is to measure the current through the alternator when the car is switched off, it should be very nearly zero

Check the 'Bat' / 'Charge'/ 'Alt' indicator on the dash panel lights when the vehicle ignition is switched on prior to starting the engine.
This indicator should extinguish within approx 1 second of starting engine.

If the indicator is not operating the alternator cannot provide charge current - check:-
1) the wiring connections to the new alternator,
2) the indicator lamp is not blown,
3) the alternator is properly grounded.

If the indicator light works normally, check the output voltage of the alternator is approx 14.5v when the motor is running.
If its about 14.5v, the battery should be charging.

you need to put a chevy alternator with a built in regulator on it.
You need a 3 wire alternator. Two wires go to the battery and one wire goes to anything connected to the ignition switch.

the wire that tells it to excite is the battery wire to the alternator through the light bulb
not charging is a problem voltage regulator
while the alternator may be new if it requires an external regulator or internal regular is a problem

Q1. Engine will not start or is hard to start (Cranks OK) A1 -Ignition lock switch faulty -Ignition coil faulty -Power transistor faulty -Spark plugs faulty -Ignition wiring disconnected or broken -Spark plugs faulty Q2, Engine will not crank A2. Battery discharged Battery cables loose, corroded or worn out Transaxle range switch faulty (Vehicle with automatic transaxle only) Fusible link blown Starter motor faulty Ignition switch faulty Ignition lock switch faulty REMEDY Charge or replace battery Repair or replace cables Adjust or replace switch Replace fusible link Repair starter motor Replace ignition switch Replace ignition lock switch