Regulator For Generators

The Voltage regulator is a critical part of your charging system. There are so many different types of regulators out there. It can be confusing trying to determine if yours is working or not. And if not what kind of regulator do you need. This article will cover basic operation and testing procedure for voltage regulators used with model 58,61, 65, 65A and 65B Harley Davidson generators. They where used from 1958 to 1984. These are two brush, exited field, commutated DC generators.

There are three things these voltage regulators need to do. As the name would suggest a voltage regulator should control voltage, but that is not its only function. A good regulator should limit current to protect the generator from over heating. It also needs to prevent the battery from discharging throw the generator when the generator is not spinning.

The regulator monitors the main power output from the generators “A” terminal. Then it controls the output by varying field current from the generators “F” terminal. If the generator output is low the regulator turns on the field. When the field is on the generator produces full power. When the voltage or amperage reaches the point the regulator is set at the regulator will shut the field off. The Generator output will go low. This cycle repeats its self over and over several times each second. The generator will ether be putting out maximum allowable current or maintaining voltage.

Mechanical Regulators

From 1958 to 1976 all Harley Davidson’s with a generator came stock with a mechanical regulator. These regulators fall into one of two categories. They are commonly referred to as the Bosch style or the Delco style. Back when Bosch and Delco where making mechanical regulators they used quality materials. These regulators worked well and they where dependable. The Delco Corporation is not in existence any more. I do not know if Bosh is still making mechanical regulators. Most if not all of the mechanical regulators made today are copies that come from Asia. That is why we refer to them as the Delco style or the Bosh style. Unfortunately many of the copies use inferior materials and seem to be less durable and somewhat undependable. It seems the art of the mechanical regulator has been lost.

Mechanical regulators use electro mechanical relays to control the generator output.
 The Bosch style are two-poll regulators. One poll controls voltage and the other poll is a cutout relay. The cut out relay opens when the generator is not spinning to prevent battery discharge. 
The Delco regulators are three-poll regulators. One poll controls voltage, the second poll is used to limit current and the third poll is a cutout relay. 
The main difference between these two regulators is the Delco can limit current and the Bosch cannot. 

Most 1964 and earlier 6-volt motorcycles came stock with a Bosch two-poll regulator. These bikes did not use enough electrical current to overheat the generator. Polices bikes came with a three-poll Delco regulator. This was necessary because the extra load from the lights, sirens and radio could draw enough power to overheat the generator.

1965 and later 12-volt electric start models all came with the Delco three poll regulator. Kick-start models with a small battery still came with a two-poll Bosh. The main difference is the size of the battery. The larger battery required for electric start could draw 20 amps for long enough to burn up a generator. I recommend always using a current limiting regulator.

 Electronic Regulators

In 1977 some Sportster started using an electronic regulator. All 1978 to 1984 Sportster came stock with electronic regulators. I am not sure when the first electronic regulators for generators where made. I do know in the beginning they where not as dependable as the mechanical regulators of that time. Electronics have come a long way over the last 30 years. At this time the average electronic regulator is more dependable than its mechanical counter part made today. But it is important to note that all electronic regulators are not created equal. There are still many cheep poorly designed regulators being made.

The best way to test a regulator is to hook it to a kwon-working generator. So the first thing to do is test the generator. I covered that last month. After determining the generator is working be sure the regulator is installed and wired properly.
Voltage test

Measuring system voltage is simple. Connect a voltage meter across the battery terminals and rev the engine to about 1500 RPM. Determining what the reading means is a little more complicated. Harley Davidson specifications for voltage on 12 volt models of that era is 13.8 to 15.8 this is a very wide rang. At Cycle Electric Inc. we believe one size dose not fit all. On electric start generator bikes we like to see 14.2 to 14.7volts. On kick start bikes, which typically have smaller batteries we like to see 13.7 to 14.00 volts. On 6-volt models you should get between 7 and 8 volts. Preferably 7.2 to 7.6. If your voltage reaches and maintains an acceptable level the voltage portion of the regulator is working.

On generator models the voltage at the battery may not come up to the normal operating level right away. In fact after using the electric starter it may take up to 20 minuets of ridding before the battery reaches normal operating voltage. Their are other factors that can keep the voltage from coming up. I wrote an article covering this subject. See testing charging voltage in my article in the may/June issue.

Current limitation

I cannot over state the importance of current limitation. The model 65A is rated at 10 amps and the model 61 at 15 amps. They are both capable of producing 20-30 amps. For this reason it is very important to have a properly working current limiting regulator to restrict amperage draw on the generator to (10 amps on the model 65 and 65A, 15 amps on the model 58 and 61).

Connect a voltmeter across the battery. Connect an ammeter in series with regulator output (measure amperage in the wire from the regulator to battery). Start the motor and bring the RPM’s up to about 2500. Connect a load dump across battery. (Add light bulbs, resistors or whatever you are using for a load dump) Continue to add load until the voltmeter reads below 13 volts. Read the ammeter. 6-volt models should not exceed 16 amps. 12-volt models should not exceed 11 amps.

Draw test
The regulator should not draw more than .002 amps or 2 milliamps from the battery when the motor is off. Use an ammeter to check for a draw between the regulator B+ terminal and the battery

If a regulator fails in a full-fielded state the generator will overheat and burn up. Due to the lack of quality mechanical regulators being made today, I recommend using a good quality electronic regulator. If you are doing a restoration on a bike that wont see a lot of miles, try to find an old stock regulator. If you plan to ride it, use a high quality electronic regulator and hide it. You can take the guts out of a mechanical regulator, month it in the stock position and use it as a junction block for your wire connections.

Let the road you chose to ride bring you happiness
Karl S Fahringer
President Cycle Electric Inc.