When i replace a new alternator and voltage regulator do i need to polarizing it?

If you can use a new wire and they charge the battery then most likely you have a broken wire in the harness that runs between the alternator and the regulator.

How old is the battery?

1979 CB300 or B300? It's been many years so I really don't remember but, it sounds like the voltage regulator has stopped working. Like I said, I can't remember but the voltage regulator is either built into the alternator or it's mounted on either the fender near the battery or on the firewall. This is a simplified schematic but you should understand. Also once you find the voltage regulator see if you can remove the cover and clean the contacts before you go and buy a new one. Hope this helps.

Due to the nature of the battery technology used with vehicles the alternator is mostly incapable of charging the battery. The car alternator is designed to keep a fully charged battery fully charged and to provide all the power for the car equipment.

The alternator charge rate is regulated by a voltage regulator. Because the alternator output is connected to the battery, the alternator and battery voltage will be the same and the voltage regulator monitors that voltage.

The lower the battery voltage the more output the alternator will produce in order to correct the situation but because a lead acid battery has a high internal resistance to accepting a charge the terminal voltage will quickly rise to the alternator regulated voltage and fool the alternator into thinking the battery is fully charged when the output will drop to the order of just a couple of amps.

Switch on the headlights or a similar load that will lower the battery voltage and the alternator will increase it's output again - but only by the amount of current the headlamps or other load is consuming.
It matters not what the alternator rated maximum output is, it is designed to provide only the necessary current and no more.

The only time an alternator should ever need to produce maximum output is when on a dedicated testbed and then only for a short duration to avoid damaging the unit. Testing the current output on a modern vehicle is not recommended except for the regulated voltage testing and a rule-of-thumb output test where all equipment is switched on and the engine speed raised while the battery voltage is monitored.

Most modern alternators use an internal voltage regulator but a few systems use a separate voltage regulator. No alternator rebuild would be complete without a regulator test and probably a new or replacement regulator, which is where the majority of charging system problems are, or the brush gear.
Assuming the wiring is ok, no alternator should suffer any harm if the voltage regulator and auxilliary diodes (if fitted) are in good order though fitting a defective or a discharged battery can cause it to overheat and be damaged.

The alternator usually just about stops producing an output when the battery voltage is in the region of 14.5/14.8 volts.
Your description indicates the voltage regulator is not working correctly - unless 40 amps was being consumed by the car equipment the alternator should not have been producing 40 amps.. I suggest you also have your battery tested

ALTERNATOR PRECAUTIONS

To prevent damage to the alternator and regulator, the following precautionary measures must be taken when working with the electrical system.

1. NEVER reverse the battery connections. Always check the battery polarity visually. This is to be done before any connections are made to ensure that all of the connections correspond to the battery ground polarity of the car.
2. Booster batteries must be connected properly. Make sure the positive cable of the booster battery is connected to the positive terminal of the battery which is getting the boost.
3. Disconnect the battery cables before using a fast charger; the charger has a tendency to force current through the diodes in the opposite direction for which they were designed.
4. NEVER use a fast charger as a booster for starting the car.
5. NEVER disconnect the voltage regulator while the engine is running, unless as noted for testing purposes.
6. Do NOT ground the alternator output terminal.
7. Do NOT operate the alternator on an open circuit with the field energized.
8. Do NOT attempt to polarize the alternator.
9. Disconnect the battery cables and remove the alternator before using an electric arc welder on the car.
10. Protect the alternator from excessive moisture. If the engine is to be steam cleaned, cover or remove the alternator.

TESTINGThere are several checks that can be done with inexpensive equipment. The first thing to do is to see if the discharge warning light on the dashboard lights when the ignition switch is turned on. If it is not lit, check for blown fuses, a blown out bulb itself (The system will not charge with a bad bulb) or bad connections.
If the warning light does light with the ignition switch on, but stays on with the engine running, check for a loose (or missing) belt, a loose or faulty battery cable, corrosion, a blown fuse or fusible link or a shorted or open wire.

If everything seems to be good (including the battery), but the charge light is always on, then the alternator itself probably is to blame. This does not mean the whole alternator needs to be replaced. Many times, the IC regulator can become faulty and cause the no-charge condition. There is a way to determine whether just the IC regulator or the whole alternator should be replaced.

The alternator can be "full-fielded;" that is, the F terminal can be shorted to ground, making the alternator think there is a heavy load on the electrical system. If the alternator starts putting out when the F terminal is shorted to ground, then the IC regulator is probably faulty. If the alternator still does not put out when the F terminal is grounded, then the whole alternator should probably be replaced. It can be concluded that the alternator is "putting out" by observing the voltage of the battery. The system is charging when the battery voltage is approximately 14-15 volts. If it is only 12-12.5 volts, something is wrong. If the charging voltage is too high (more than 15 volts, the battery smells like sulfur or frequently runs out of water or the bulbs in the vehicle burn out too frequently, then the IC regulator is probably faulty (See Regulator).

Check the alternator and IC regulator by performing the following:

1. Ground the F terminal on the alternator.
2. Start the engine.
3. Analyze the voltage, using the information above.
   

Fig. 1 Checking the alternator and IC regulator 2S-E, 3S-FE and 3S-GE engines shown



Fig. 2 Checking the alternator and IC regulator 4A-FE, 5S-FE and 3S-GTE engines shown




Hope this help (remember rated this).

You dont. Alternators DO NOT require polarisation as they can only be fitted to vehicles that are wired as NEGATIVE EARTH. If you have replaced the Alt, reconnect the wiring, reconnect the battery - Positive lead first then the negative lead, then start the motor !! Using multimeter, check the charge rate at the battery. It should be around 13.8 volts. The charge rate SHOULD NOT go above 14.7 volts and if it does, turn the motor off immediately and recheck the connections, especially any battery voltage sensing wires. if nothing appears to be wrong, contact an auto electrician and have them check things out. I have known faulty regulators, even in new Alternators..

The issue could due to the voltage regulator not working properly.

If the wires have been replaced correctly to the alternator, look for a metallic box near the alternator, probably on the fender wall.

The price for the voltage regulator should be around $20.00.

It is a good idea to replace the voltage regulator when you replace the alternator, since both are probably the same age.

Hope this helps!

try this add an extra braided ground strap
i assuming you have all ready tested the out put of new alternator?? NEW doesn't mean it works .
assuming you done filed and diide continuity
checked and the polarity of alt,bat and regulator are all the same you added extra ground strap from block to fire wall. battery checks out. still no charge.get a new battery with more cold cranking amps.

Are the connections really dirty at the voltage regulator? These tend to get corrosion on them and cause weird charging system issues. Also make sure the ground is good on the regulator.

Check your Belt and see how tight it is. It may be Tight just not tight Enough to Fully Charge the Battery with the Alternator.