Tractor Alternator Supply for most makes

Tractor & Combine Alternators * Agricultural & Industrial Engine Alternators

Supplier of 12v or 24v Tractor alternators brand new outright with a full 12 month warranty*
or factory service exchange alternators rebuilt to manufacturers specification carrying manufacturer standard warranty*
Please contact us or use the enquiry form below for replacement alternator prices.
If you require alternator repair component parts visit Alternator Parts page

Local breakdown callout for Tractor Alternator fitting & autoelectrics

Alternator supply & fitting service (on site where possible) available in local Shrewsbury Shropshire & Welshpool Mid Wales areas.

On Site Fitting

We find that many agricultural businesses have personnel with engineering skills or know of a local Agricultural engineer capable of alternator fitting.
Many tractor alternators can be removed and replacement fitting undertaken on site.

Alternator and Battery charging system diagnostic testing available for troubleshooting of alternator charging circuit problems
Auto electrical diagnostics  wiring faultfinding and repair.

Alternator Wiring Terminal Letter Guide

B+ , 30, Battery Positive
S, M, 2, Battery Voltage Sense
B- , 31, D-,GRD Battery Negative
F, DF , 67 , FLD , EXC, Field/Rotor
D+, 61 , L , IND, Charge Warning Lamp
IG, 15 , R , Ignition
N, C, Central Point
W, P, STA, Tachograph rev counter (stator single phase tap AC output)
Please Check the manufacturers instructions for specific application of wiring terminal designation.

Tractor Alternator Basics

Tractor Alternator Function :

The tractor's engine driven alternator generates electricity providing power to recharge starter battery and supply electrical power for tractor & machinery electrical and electronic systems such as lighting, wipers, heater motor, radio, camera system, gps radar, electromechanical systems etc whilst the vehicle engine is running.

Tractor alternators generate AC (alternating current ) rectified to DC (direct current) by diode pack (rectifier)

Alternator pulley is rotated via auxilliary belt rotation
Insecure missing or damaged mounting brackets can mean loss of drive belt tension (slips & causes a squealing sound!) and reduction of alternator performance.

Alternator excitation

A small electrical Current is supplied to the tractor alternator to excite the rotor windings enabling a magnetic field. Without excitation there will be no magnetic field and the alternator will not charge.
Some alternators are self excited, this means after the rotor is initially excited by a wire connected to the stator which taps some of the power generated to maintain rotor excitation and power generation whilst the alternator rotor spins.
Excitation power is connected to the rotor via carbon brushes which contact the copper slip rings of the spinning rotor creating a magnetic field.
Worn out brushes or excessive slip ring wear may cause loss of alternator charging output.

Tractor alternator voltage regulation

Excitation current control to the rotor proportionally controls magnetic field strength and alternator output.
The voltage regulator switches excitation current on / off to control generator voltage output.

Modern tractors may be fitted with high output alternators having dynamic electronic control of the voltage regulator. Alternator output may be affected by the embedded software in a powertrain control computer. These high output types of alternator may have a terminal marked BSS, Com, or LIN, etc. Dedicated specialist diagnostic test equipment may be required to check and verify.

Stator output Current - Rectification from AC to DC

Direct current is required to allow battery recharging. Alternating (AC) Current is rectified to Direct Current (DC) by the Diode pack.
Tractor alternators are 3 Phase AC generators with rectification to DC.
when the ignition key is off, the diode pack has a second function to block battery discharge via power drain through alternator windings.

Tractor Alternator Fault Diagnosis:

Symptoms

Battery charge warning light illuminated or flashing whilst the engine is running.
Gradual loss of battery electrical power until the fuel pump solenoid closes fuel supply may cause the engine to stop.
Electrically controlled implements may cease to function normally due to low battery voltage.
Discharged battery prevents starter motor operation.

Basic Alternator Checks

With the engine stopped visual checks may be carried out to ensure the alternator is secure and drive belt correctly tensioned.
Check for oil ,fuel or coolant leaks which may have caused the alternator failure.
Beware of short circuiting metal tools to ground if checking tightness of electrical connections.
Check wiring insulation is in good condition.
All heat shields should be intact.

Use a multimeter to check voltages at battery and alternator.

Batteries should be tested using a proper battery tester eg Bosch BAT121.

A quick check for a failed alternator is to measure battery voltage with the engine off using a voltmeter.
Start the tractor engine and run at around 2000rpm whilst monitoring battery voltage which should have increased slightly as the alternator charges the battery.
Check voltage at B+ terminal of the alternator reads close to battery voltage

Incorrect alternator output voltage ( alternator overcharging or undercharging ) can affect sensitive tractor and farm machinery computers and related systems.

Typical battery voltage for a 12 volt system:
Engine off: 12.5 volts
Engine running at 2000 rpm : 13.2 to 14.6 volts at battery(regulated voltage)
Alternator overcharging: A battery voltage above 15 volts with the engine running on a standard 12v charging system often indicates an alternator voltage regulation fault causing overcharging of batteries and premature failure. OE manufacturers specification should be checked to verify.

Excessively Noisy Alternator : possible causes:
V drive belt tension incorrect
Bearing failure
Alternator Stator winding fault causing phase imbalance

How long should my tractor alternator last ? Tractor Alternator Failure : Common causes

Normal lifespan of a tractor alternator is dependant on environmental and operational conditions.
Tractors have hard working engines which means hotter engine temperatures.
Inadequate ventilation : Farm machines often operate in dusty conditions where during operation the cooling fan of the alternator causes chaff and dust to be drawn in, a build up of foreign matter or chaff may cause the alternator to overheat and fail.
Engine oil leaks onto the alternator will cause premature failure the unit.
Water, coolant leaks, or high pressure jetwashing may cause the alternator to fail prematurely.
Corrosive substances found in agriculture may cause the alternator to fail prematurely.

Wiring connections - cable breaks - Poor electrical connection causing high circuit resistance and leading to overheating.
Wear and tear ; Worn out brushes ,sliprings, bearing failure, diode pack failure.
Excessive drive belt tension causing premature bearing failure.
Drive belt too loose
Alternator is bracket mounted to engine : Cracked brackets, or missing or insecure mounting bolts / bracket may cause insufficient drive belt tension.
Electrical overload due to a defective battery, auxilliary loads, fitment of non standard accessories, or vehicle wiring faults.
Voltage surge caused by boost starting using jump leads without surge protection can cause voltage spikes and damage to alternator diodes.
Chemical, oil, fuel or coolant leaks onto the alternator.
Battery cell shorted / Incorrect battery specification may cause problems.

Alternators for Tractor Makes
ALLIS CHALMERS
BELARUS
CASE
CATERPILLAR
CLAAS
DAVID BROWN
DEUTZ FAHR
FENDT
FERGUSON
FORD
FORDSON
FIAT
IMT
INTERNATIONAL HARVESTER
IVECO
JCB
JOHN DEERE
KRAMER
KUBOTA
LAMBORGHINI
LANDINI
LAVERDA
LEYLAND
MANITOU
MARSHALL
MASSEY FERGUSON
MATBRO
MERCEDES ENGINE
MERCEDES MBTRAC
MERCEDES UNIMOG
MUIRHILL
PERKINS
MITSUBISHI
NEW HOLLAND
SAME
SANDERSON
VALMET
VALTRA
VOLVO
ZETOR