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Discussion Forum
Show Parts for Model:

Farmall Generator & Regulator Tests - 6 & 12 Volt

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SadFarmall

04-25-2011 07:16:02
124.181.79.85



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There are many questions placed on this forum about generator and regulator issues. The following may help for both 6 and 12 volt systems set up with generator and regulator charging systems.

1). Always check that wiring and instruments (ammeter / voltmeter) are in good order and operate correctly.

2). Ensure that all connections are good, tight and clean.

3). Ensure that the battery is in a satisfactory condition and that the connections to it are tight and clean, especially the connection to Earth.

There are basic tests to check generator and voltage regulator operation:

Test 1): Disconnect leads from generator. Connect one lead of a Voltmeter to the Main (or D) terminal and the other lead to Earth. Start the engine. Run the generator up to approx. 3,000 rpm.

Result:

a).Voltmeter reads 2-4 Volts = armature and brush connections OK (6 and 12 volt systems)

b). Voltmeter reads 0 Volts = Check brushes are in good condition and make good contact with commutator. If brushes are good and reading remains at zero, the armature is defective.

c). Voltmeter reading rises with engine speed = short circuit between Main (or D) and Field (or F) terminals. Field coils defective.

Test 2): Disconnect leads from generator. Connect Main (or D) and Field (or F) terminals to each other. You can use an ammeter to do this. (The ammeter should read no more than two 2 amps. Connect one lead of a Voltmeter to the Main (or D) terminal and the other lead to Earth. Start the engine. Gradually increase engine to a fast idle speed.

Result:

a). Rising volts with rising speed and full scale reading at fast idle = generator is in good order.

b). 2-4 volts as engine speed increases = open circuit in field coils. Field coils defective. (6 and 12 volt systems)

c). 0 volts = grounded field coils or field connection. Repair connection and/or replace field coils.

Test 3): Check leads are correctly connected to generator terminals. Disconnect Main (or D) and Field (or F) leads from voltage regulator. Connect one lead of a Voltmeter to the end of the Main (or D) lead and the other to Earth. Start engine and run generator at approx. 3,000 rpm.

Result:

a). 2-4 volts = lead from Main (or D) terminal on regulator to Main (or D) terminal on generator is in good order. (6 and 12 volt systems)

b). 0 volts = lead from Main (or D) is open circuited or Earthed. Rewire this lead.

c). Rising volts with rising speed = short circuit between Main (or D) and F leads. Find short circuit and rectify.

Test 4): Check leads are correctly connected to generator terminals. Disconnect Main (or D) and Field (or F) leads from voltage regulator and connect them together. Connect one lead of a Voltmeter to the end of the Main (or D) lead and the other to Earth. Start engine and run up to fast idle speed.

Result:

a). Rising volts with rising speed = leads from generator to regulator are in good order.

b). 0 volts = field lead is Earthed. Find where it is Earthed and rectify.

c). 2-4 volts (6 and 12 volt systems) = open circuit in field lead between generator and regulator. Find damaged section of lead and rectify.

Test 5): Ensure all connections to generator and regulator are clean and tight. Connect one lead of a Voltmeter to the Ammeter (or A) terminal of the regulator. Connect the other lead of the Voltmeter to the Earth (or E) terminal of the regulator. Do not start the engine.

Result:

a). Voltage same as battery voltage = regulator ground connection is in good order.

b). Voltage less than battery or zero reading = regulator ground connection is poor or non-existent. Check connection and Earth wire if fitted.

Do NOT carry out the following test with the battery in circuit!

Test 6): Remove the regulator cover. Place a piece of dry card between the cut-out contacts to isolate the battery. Connect one lead of a voltmeter to the Main (or D) terminal and the other lead to Earth. Run generator at approx. 3,000 rpm:

Result:

a). For 6 Volt Systems:

ambient temp of 50-70F reading is 8-8.5 volts

ambient temp of 85 - 105F reading is 8.0 volts

= regulator is in order

b). For 12 Volt Systems:

ambient temp of 50-70F reading is 16-16.5 volts

ambient temp of 85 - 105F reading is 15.5-16 volts

=regulator is in order

c). Voltage remains constant, but outside limits given in a) and b) = regulator (NOT cut-out) requires adjustment.

d). Rising volts with rising generator speed up to 3,000 rpm and beyond = short circuit between Main and Field leads or broken shunt winding in regulator bobbin. To check regulator bobbin, place a screwdriver above it. If there is no magnetic pull, regulator is defective. Replace it.

e). Reading approx. half what it should be = regulator contacts corroded or burnt. To test, bridge regulator contacts. This will close the circuit between the Main and Field terminals. If you see rising volts with rising engine speed now, this proves the regulator contacts are defective.

f). Voltage does not rise with engine speed or is erratic = air gap settings on bobbin and regulator contacts are incorrect. Recitfy by setting to manufacturers specifications.

Test 7): Do not run engine for this test.

Remove card from cut-out contacts. Connect one lead of a voltmeter to the Ammeter (or A) terminal on the regulator and the other lead to Earth (not the Earth or E terminal on the regulator).

Result:

a). Voltmeter shows battery voltage = connection between the battery and ammeter terminal on regulator is good

b). Voltmeter shows zero voltage = connection between battery and ammeter terminal on regulator is open circuited

c). Voltmeter shows less than battery voltage = connection between battery and ammeter terminal on regulator is poor.

Test 8: Same as Test 7, but with engine running.

Result:

a). As the cut-out closes the reading increases by 0.5 to 1 Volt above battery voltage and increases to the correct regulator voltages in Test 6 = cut-out is in order

b). zero voltage or very low voltage shown when cut-out closes = dirty or poorly adjusted cut-out contacts. Clean and adjust.

Test 9): Connect one lead of a voltmeter to the Main (or D) terminal on the regulator and other lead to a good Earth. With Engine running:

Result:

a). For 6 Volt Systems

Cut-out points close at 6.3-6.7 Volts = Cut-out in good order

b). For 12 Volt Systems

Cut-out points close at 12.7-13.3 Vots = Cut-out in good order

c). Cut-out points close outside limits in a) and b) = cut-out out of adjustment. Adjust cut-out and test from zero voltage.

d). Cut-out does not close = defective cut-out. Replace cut-out.
This post was edited by SadFarmall at 07:16:42 04/25/11.

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SadFarmall

04-28-2011 00:02:28
121.214.172.55



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 Re: Farmall Generator Regulator Tests - 6 12 ... in reply to SadFarmall, 04-25-2011 07:16:02  
Happy to put up the information. Sorry to anyone who objects to Earth instead of chassis or common or frame. Must be my evil Lucas electrics background.



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Picklesmith

04-25-2011 10:56:17
24.35.163.46



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 Re: Farmall Generator Regulator Tests - 6 12 ... in reply to SadFarmall, 04-25-2011 07:16:02  
SadFarmall-

Just a short note to thank you for posting a concise, systematic method for determining problems with generators/regulators on Farmall tractors.



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55 50 Ron

04-25-2011 08:19:57
206.9.215.61



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 Re: Farmall Generator Regulator Tests - 6 12 Volt in reply to SadFarmall, 04-25-2011 07:16:02  
Earth???
On a vehicle there is no earth, it's known as chassis or frame or common.



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