Electrical System Information

(Ford Tractors 1953-1962)

The following information has been complied from various Ford Tractor Service manuals and publications.  A list of this reference material may be viewed on the Sources page.



  1. Battery Maintenance
    1. Table: Battery Specific Gravity Charge
  2. Battery Removal
  3. Battery Installation
  4. Battery Charging

Generator and Charging Circuit

  1. Generator Output Test
  2. Voltage Limiter and Cutout Tests
    1. Table: Voltage Limiter Settings
  3. Generator Removal
  4. Generator Installation

Generator Regulator

  1. Generator Regulator Removal
  2. Generator Regulator Installation
  3. Polarizing the Generator

Starting Motor, Solenoid, and Starting Circuit

  1. Starting Motor Removal
  2. Starting Motor Installation

Starting Motor Relay

  1. Starting Motor Relay Removal
  2. Starting Motor Relay Installation

Troubleshooting the Electrical System

  1. Generating System
    1. Battery Low In Charge
    2. Generator Output Low
    3. High Charging Rate
  2. Starting System
    1. Engine Will Not Crank
      1. Test #1
      2. Test #2
    2. Starting Motor Spins But Does Not Crank Engine
    3. Engine Cranks Slowly

Specifications and Wiring Diagrams

  1. Electrical System Specifications
  2. Electrical System Wiring Diagrams
    1. Wiring Diagram- 6 Volt Positive Ground
    2. Wiring Diagram- 12 Volt
    3. Negative Ground


Electrical System


The electrical system on Ford tractors consists of the starting system, the charging system, and the ignition system (gasoline and LP-gas systems only).  All gasoline and LP-gas powered Ford tractors utilize a six-volt positive ground electrical system.  All diesel powered Ford tractors utilize a twelve-volt negative ground electrical system.




The storage battery converts chemical energy into electrical energy.  The battery is the source of all current in the Ford tractor electrical system.  The primary function of the battery is to provide current for the ignition and starting systems.  The generator replenishes the charge in the battery.  In addition to keeping the battery charged, the generator supplies current for ignition, lights, and electrical accessories.


Battery Maintenance


1.        Check the level of the electrolyte at regular intervals.  If the electrolyte level is low, bring to proper level by adding distilled or purified tap water.

2.        Battery terminals should be kept tight and free of corrosion.  Clean the battery terminals, battery case, and battery support with a solution of two tablespoons of baking soda mixed with one pint of water.

    1. Plug all battery vent holes to prevent the cleaning solution from entering the battery.
    2. After cleaning, rinse the cleaning solution away with clean water.
    3. Apply a small amount of petroleum jelly to the battery terminals to prevent corrosion.
    4. Remove plugs form vent holes.

Battery Specific Gravity Charge


State of Charge

Specific Gravity

Fully Charged


75% Charged


50% Charged


25% Charged





Hydrometer readings will be accurate in temperatures from 70 degrees F. to 90 degrees F.  Readings must be corrected to .004 specific gravity for each 10 degrees F. For every 10 degrees F. above 80 degrees F. add .004 specific gravity points. For every 10 degrees F. below 80 degrees F. subtract .004 specific gravity points.  Many hydrometers have a thermometer and correction scale built in so that a temperature correction can be properly made.


Battery Removal

  1. Disconnect the battery ground cable.
    1. On gasoline and LP-gas powered Ford tractors, disconnect the positive (+) cable.
    2. On diesel powered Ford tractors, disconnect the negative (-) cable.
  2. Remove the nut and washer from each hold-down clamp bar and remove the bars.
  3. Remove the battery and hold-down clamp from the battery support.  Lift the clamp from the battery.
  4. Inspect the battery support for corrosion and clean (refer to maintenance procedures outlined above) or repair as necessary.

Battery Installation


Ensure the battery electrolyte is at the proper level (refer to maintenance procedures outlined above) and that the battery is fully charged.

  1. Position the hold-down clamp on the battery.  Place the battery on the battery support.
    1. On six-volt systems, the positive post of the battery must be toward the right side of the tractor.
    2. On twelve-volt systems, the negative post of the battery must be toward the right side of the tractor.
  2. Secure the battery with the two hold-down bars, washers, and nuts.  Tighten the nuts only enough to keep the battery from shifting.
  3. Connect each battery cable to its respective cable.  Always connect the ground cable last!

Charging the Battery

  1. Wash all dirt from the battery and clean the battery terminals before placing the battery on charge.  Open the individual battery cell caps, ensuring that dirt does not enter the battery cells.  Bring the electrolyte level in each cell up to the proper level (to the fill ring).  If the battery is cold, allow the battery to warm before adding distilled or purified water to the battery cells, as the electrolyte level will rise as the battery warms up.
  2. Slow charging at a rate of 3 to 4 amperes is the only method that will fully charge the battery.  The battery is fully charged when the cells are all out gassing (releasing tiny bubbles into the electrolyte, visible through the battery cell filler holes) and the specific gravity remains at the same level for three successive readings taken at hourly intervals.  Do not stop charging short of the fully charged state, as this may develop a "shallow" charging cycle.  A battery which is badly sulphated may not take a charge or will require more charging time than a normal battery.  A badly sulphated battery should be replaced.
  3. A "fast charger" may quickly "boost" a battery without removing the battery from the tractor.  A high rate charger may also be used to "boost" a battery.  A high rate charge must always be followed by slow charging for the length of time necessary to bring the battery to full charge.  Warning: charging the battery at a high rate will cause the temperature of the electrolyte to rise and may cause violent out gassing of the electrolyte.

Generator and Charging Circuit

The charging circuit consists of the battery, generator, generator regulator, charge indicator light (if so equipped) and the necessary wiring.  A shunt wound two pole type generator provides the electrical energy necessary to keep the battery fully charged.  The generator output is controlled by a two unit regulator consisting of the cutout relay and a voltage current regulator.

Before attempting any repairs on the charging circuit, ensure that the fan belt tension is properly adjusted and that the terminal connections are tight and free of corrosion.  Perform the following tests to determine which unit is faulty:


Generator Output Test

  1. Disconnect the armature (red) wire from the terminal on the generator.  Connect a jumper wire across the armature and field terminals.  The field terminal is located on the side of the generator case.
  2. On six-volt systems, connect the negative lead of an 0-75 ammeter to the generator armature terminal.
  3. On twelve-volt systems, connect the positive lead of an 0-75 ammeter to the generator armature terminal.
  4. Connect the other ammeter lead to the terminal of the armature (red) wire.
  5. Start the engine and gradually increase the engine speed to approximately 1500 RPM while observing the ammeter.  The generator output should reach or exceed 20 amperes.
  6. Stop the engine and disconnect the jumper wire from the field and armature terminals as soon as the generator output is observed to prevent overheating of the generator.
  7. If the generator output is below 20 amperes or ammeter readings are observed to be erratic, check the generator belt tension and adjust as necessary.
    1. To adjust the generator belt tension, loosen the two generator pivot bolts located at the base of the generator.  Loosen the belt tension adjusting bolt nut.  Move the generator away from the engine until a 1/2" belt deflection is attained.  Proper adjustment is important.  An over tightened belt may cause premature wear of the generator armature shaft bearings.  A loose belt may result in belt slippage, poor generator performance, and an overheated engine. 
  8. If adjusting the belt does not increase the output of the generator to 20 amperes or more, remove and repair or replace the generator.

Voltage Limiter and Cutout Tests

  1. Before checking the generator regulator, the following electrical system components must be checked:
    1. The wiring harness must be carefully inspected and all connections must be checked for cleanliness and tightness.  Corroded and/or dirty terminals cause high circuit resistance which degrades the overall performance of the system.  Bare wiring must be repaired or replaced.
    2. The generator output test, outlined above, must be performed to ensure the proper performance of the generator.
    3. The specific gravity of the battery must be checked to determine the state of battery charge.  If the specific gravity of the battery is below 1.250 (adjusted for temperature), the battery must be fully charged or replaced with a fully charged battery.  Procedures for checking the specific gravity of the battery are outlined above.
  2. With the ammeter wires connected to the generator in the same fashion as in the generator output test (with the exception of the jumper wire across the armature and field terminals), connect the voltmeter negative lead to the ammeter positive lead.  If working on a twelve-volt system, connect the voltmeter positive lead to the ammeter negative lead.  Connect the other voltmeter lead to ground.
  3. Start the engine and allow the engine to idle until the regulator reaches normal operating temperature.  Normal operating temperature of the regulator may be obtained by a 30 minute run at a 4.5 to 5.0 amp charge rate.
  4. When normal regulator temperature is attained, slowly increase the engine RPM to approximately 1500-2000 RPM while closely observing the ammeter and voltmeter.  Cutout closing will be indicated by a "flick" or momentary drop of the  voltmeter pointer and a rise of the ammeter pointer.  The voltage indicated at the time the voltmeter "flicks" or momentarily drops back is the cutout closing voltage.  The cutout closing voltage should be 6.0-6.6 volts on a six-volt system with the regulator at 80 degrees F. or 12.2-13.0 volts on a twelve-volt system under the same temperature conditions.  It may be necessary to repeat this test several times to note the "flicking" of the voltmeter pointer.
  5. Replace the voltage regulator if the cutout closing voltage is not within specifications.
  6. Read the regulated voltage on the voltmeter which is connected from the regulator "arm" terminal to ground.   When the generator regulator test is completed, disconnect the test leads and connect the armature wire to the armature terminal on the generator.  
  7. Refer to the following table to determine the correct setting of the voltage limiter for various temperatures (indicated in degrees Fahrenheit) when tested with a current of 4.5 to 5.5 amperes:


Voltage (six-volt system)

Voltage (twelve-volt system)


7.65 - 8.05

15.15 - 15.95


7.60 - 8.00

15.1 - 15.9


7.55 - 7.95

15.05 - 15.85


7.50 - 7.90

15.0 - 15.80


7.45 - 7.85

14.95 - 15.7


7.40 - 7.80

14.9 - 15.7


7.35 - 7.75

14.85 - 15.65


7.30 - 7.70

14.8 - 15.6


7.25 - 7.65

14.75 - 15.55


7.20 - 7.60

14.7 - 15.5


7.15 - 7.55

14.65 - 15.45


7.10 - 7.50

14.6 - 15.4


7.05 - 7.45

14.55 - 15.35


7.00 - 7.40

14.47 - 15.27


6.94 - 7.35

14.4 - 15.2


6.90 - 7.30

14.33 - 15.13


6.85 - 7.25

14.25 - 15.05


Generator Removal

  1. Disconnect the armature, field, and ground wires at the generator terminals.
  2. Remove the adjustment arm to generator bolt, the generator belt, and the two pivot bolts from the mounting bracket.  Remove the generator.

Generator Installation

  1. Clean the mating surfaces of the generator and mounting bracket.  Install the generator in the bracket with two pivot bolts and lock washers.  Install the generator belt and the adjustment arm-to-generator bolt.
  2. Adjust the belt tension as discussed previously and tighten all bolts securely.  Install the armature, field, and ground leads on their respective terminals.

Generator Regulator


Generator regulator used on all series tractors consist of two main control units, the voltage limiter relay and the cutout relay, mounted as an assembly inside a sealed case.  Current control is obtained by winding three turns of the series winding around the voltage limiter coil.  This arrangement restricts the generator current output to a maximum of 20 amperes.

The voltage limiter holds the generator output voltage at a pre-determined value.  The voltage limiter and cutout relay are temperature compensated.  This causes the regulator voltage to vary with changes in temperature. 

The cutout relay serves as an automatic switch which connects the generator to the battery when the generator regulator reaches the value for which the output is calibrated (refer to the table above).


Generator Regulator Removal

  1. Disconnect the battery ground cable.
  2. Working through the hood top center panel, disconnect the battery wire (heavy yellow wire), the field wire (light yellow wire), and the armature wire (double red wire) from the posts on the regulator.
  3. Remove the three regulator attaching screws and the generator ground wire (black wire).
  4. Remove the generator regulator.

Generator Regulator Installation

  1. Hold the generator regulator in position on the steering gear and install the three attaching screws and ground wire (black wire).
  2. Connect the battery wire (heavy yellow wire) to the top terminal.  Connect the field wire (light yellow wire) to the center terminal.  Connect the armature wire (double red wire) to the lower terminal.
  3. Connect the battery ground cable.

Polarizing the Generator


A generator that has been repaired or tested must be polarized in respect to the battery it is to charge.  Failure to polarize the generator in respect to the battery it is to charge may result in generator regulator failure.

The generator is polarized by disconnecting the field wire and the battery wire from their respective terminals at the regulator and momentarily touching the two wires together (the engine is not running during this procedure).  This quick surge of current correctly polarizes the generator.  Reconnect the field wire and the battery wire to their respective terminals on the regulator.


Starting Motor, Solenoid, and Starting Circuit


The starting system includes the starting motor and drive assembly, the starter switch (safety control switch with Select-O-Speed equipped tractors), starting motor relay, battery, and the necessary wiring and cables.


Starting Motor Removal

  1. Diesel engine: remove the air cleaner tube and air cleaner.
  2. Remove the oil filter from the cylinder block.
  3. Disconnect the starting motor cable from the terminal on the starting motor.
  4. Remove the three bolts and lock washers that attach the starting motor to the engine.
  5. Lift the starting motor from the engine.

Starting Motor Installation

  1. Position the starting motor on the cylinder block and install the three bolts and lock washers.
  2. Connect the starting motor cable to the terminal on the armature frame.
  3. Install the oil filter.
  4. Diesel engine: install the air cleaner and air cleaner tube.

Starting Motor Relay

Starting Motor Relay Removal

  1. Disconnect the battery ground cable from the right side of the tractor.
  2. Remove the air cleaner tube.
  3. Disconnect the cables and attaching wires from the starting motor relay.
  4. Remove the nuts and washers that attach the starting motor relay to the tractor and remove the relay.

Starting Motor Relay Installation

  1. Secure the starting motor relay to the tractor with two nuts and lock washers.
  2. Connect the two cables and wires to their respective terminals on the starting motor relay.
  3. Connect the battery ground cable to the right side of the tractor.


Many of the following specifications may also be found on the Model Comparisons Page.


Model or Series















All models except diesel- 6 volt positive ground.  Diesel- 12 volt negative ground

Firing order

All models- firing order 1-2-4-3

Initial Timing














Degrees Dwell

Please refer to the notation below this table

Point Spacing

Front mounted distributor- .015     Side mounted distributor-.024-.026

Spark Plug Type

All models except LP and diesel- H-10  LP- H-8  Diesel- n/a

Spark Plug Size

All models except diesel- 14MM.  Diesel- n/a

Spark Plug Gap

All models except LP and diesel- .025-.028  LP- .028-.031  Diesel- n/a

Spark Plug Torque

All models except diesel- 24-30 ft.lbs. Diesel- n/a



Primary Ohms resistance- 1.06 to 1.17



Secondary Ohms resistance- 3800 to 4300



Capacity- 21 to 25 MFD



Minimum insulation resistance- 5 megaohms



Power factor- 0.6% @ 60 cycles


three brush

two brush shunt wound

Generator Drive

All models- V belt

Generator Capacity

All models except NAA and diesel- 20 amps., 140 watts.  NAA- 20 amps., 160 watts

Generator Test RPM


Engine RPM to test voltage, all models except diesel- 1200. Diesel- 1500 RPM

Generator Field Resist.


Field resistance @ 70º- all models except diesel- 3.2 Ohms. Diesel- 7.2 Ohms

Generator Regulator


 Cutout voltage- all models except diesel- opens @ 5.5v to 5.1v  closes @ 6v to 6.6v.  Diesel- opens @ 13v to 11v  closes @ 12.2v to 13v

Generator Regulator


Voltage limiter- all models except diesel- 7.1v to 7.5v. Diesel-15v+

Generator Regulator


Reverse current- all models except diesel- 6 amps. Diesel- 9.5 to 6 amps.

Starter Cranking Speed

All models except diesel- 100rpm.  Diesel- 180rpm

Starter Amps, no load


All models - 100 amps.

Starter amps, cranking


All models except diesel- 100-150 amps.  Diesel- 190-225 amps.


Dwell - Ford service literature is confusing, placing the dwell value @ 27º to 31º and 58º to 63º without explaining the differences in the values.  Perhaps the dwell measured at the distributor is  27º to 31º and the dwell measured at the crankshaft is 58º to 63º.