American M-Series military vehicles follow a common system of electrical circuit numbers. This simplifies maintenance procedures and training of military mechanics who have to work on many different vehicles. In some cases it allows common parts to be used for multiple applications.
M-3 tank engine wiring harness manufacture at Chrysler, World War II.
For a more complete listing of military standard circuit numbers than the table on this page, consult this file based on TACOM's Ordnance Drawing 7070301 [285k PDF download].
Today in WW II: 16 May 1940 US Pres. Roosevelt asks Congress for funding to build 50,000 airplanes per year, a startling undertaking at the time. More↓
Every electrical line in
the vehicle will have small metal tags crimped around the wire near every
junction or connector. The metal tag will bear a number and that number
uniquely identifies what electrical circuit the wire is carrying. All wiring is
black so the metal tags are the only ID for you to use, unlike color-coded
commercial vehicle wiring.
Electrical components, such as switches, recepticles, and lights may
also have the same identifying numbers. If they come with pigtails, there will
probably be a tag on each wire. If they just have a socket, the circuit number
may be part of the housing or painted on. If you make any changes to your
vehicle wiring, try to preserve the wire tags and to properly tag anything you
add. That will help you or the next owner when the time comes to try to
understand what you did. If you can stamp military style metal tags, great. If
not, use other wire label methods but use the correct numbers.
In order to help you when you service your vehicle or make any changes
to its wiring, here is the list of numbers. The information on this list was
compiled from PS Magazine, #38 (1955) and TM 9-8000 Principles of Automotive
Vehicles (1956). No one vehicle has all of these circuits and most wheeled
vehicles use only a small subset of them.
Note that not all numbers are used; if a number is skipped in the table,
it is unassigned. If you find any error in this table,
please contact Olive-Drab.com.
Wire Number
Circuit Description
1
Generator field circuit (main feed)
2
Generator armature circuit (main positive line)
2A
Alternator field, to 5A terminal on alternator
3
Generator ground circuit
3B
Alternator ground circuit
4
Generator regulator to ammeter or shunt
5
Ammeter or shunt to starter terminal block or battery
connection
5A
Battery positive to alternator main feed
6
Battery to starter
7
Battery ground including master switch if in this circuit
8
Shunt to ammeter positive
9
Shunt to ammeter negative
10
Ammeter or shunt feed to instrument panel circuit breakers
11
Ignition switch feed or magneto ground (LH)
12
Ignition switch to ignition coil or booster switch to booster
coil
13
Magneto ground (RH)
14
Starter switch circuit (including feed) to relay or solonoid
15
Main light switch feed
16
Light switch (HT) to service headlamp or dimmer switch
17
Dimmer switch to high beam service lamps
18
Dimmer switch to low beam service lamps
19
Light switch (BOD) to blackout driving lamp including
resistor
20
Light switch (BHT) to blackout marker lamps
21
Light switch (HT) to service tail lamp
22
Light switch (S) to service stop lamp
22-460
Turn signal switch to right rear stop lamp
22-461
Turn signal switch to left rear stop lamp
23
Light switch (BS) to blackout stop lamp
24
Light switch (BHT) to blackout tail lamp
25
Horn switch (including feed) to horn or horn relay
26
Horn relay feed and horn relay to horn
27
Instruments feed (instruments with polarity)
28
Fuel indicator to sending unit if single tank, or left upper tank
indicator to selector switch
29
Fuel selector switch to right upper tank
30
Fuel selector switch to left lower tank
31
Fuel selector switch to right lower tank
32
Oil level sending unit to indicator or selector switch
33
Water and oil temperature indicator to sending unit
34
Low engine oil pressure warning light circuit, including
feed
35
High water temperature warning light circuit, including feed
36
Oil pressure indicator to sending unit
37
Outlet socket
38
Dome light circuit, including breaker and switch
39
Map light circuit
40
Instrument light circuit
41
Interphone #1
42
Interphone #2
43
Interphone #3
44
Interphone #4
45
Interphone #5
46
12 Volt radio circuit, including radio master switch
47
Slip ring feed
48
24 volt radio feed
49
Receptacle, aux power outlet, positive lead
50
Receptacle, aux power outlet, negative lead
51
Interphone #7
52
6 volt tap on tail light dropping resistor to tail light
53
Electric brake control circuit
54
Fuel cut-off circuit
55
Flame primer low tension circuit
56
Flame primer high tension circuit
57
Instrument panel ground
58
Compass light circuit
58E
Voltmeter ground
59
Hull ventilating fan circuit
60
Interphone #6 (extra)
61
Auxiliary generator field
62
Auxiliary generator armature (positive line)
63
Auxiliary generator ground
64
Auxiliary generator regulator to battery, including heater
transfer switch
65
Auxiliary generator starter relay circuit, including switch and
feed
66
Auxiliary generator starter to transfer switch, including starter
or relay
67
Emergency stop switch ground
68
Battery interconnecting cables
69
Resistor to ground terminal on trailer coupling
70
Regulator ground (LH)
71
Windshield wiper circuit
72
Low transmission oil pressure indicator circuit, with feed
(LH)
73
Radio terminal box to ground
74
Starter solonoid circuit (actuating) including switch or
relay
75
Stop switch circuit (SW to SS on main light switch)
76
Fuel pump control feed
77
Fuel pump switch to fuel pump left
77B
Fuel pump safety cut-out switch (??)
78
Fuel pump switch to fuel pump right
79
Fuel tank ground
80
Ignition coil to distributor
81
Battery positive feed to starting motor terminal block, including
master switch
82
Starter motor terminal block to starter motor, left
83
Main light switch (TT) to tail light connection on trailer
receptacle
84
Main light switch (SS) to stop light connection on trailer
receptacle
85
Low air pressure indicator light
86
Ground on series parallel switch, to ammeter, including circuit
breaker
87
Spotlight circuit for trucks and wreckers
88
Winch torque limited control
89
Automatic choke
90
Trailer receptacle to ground
91
Headlamp to ground
92
Parking lamp to ground
93
Starter relay grounding circuit
94
Starter relay auxiliary grounding circuit
95
Tail lamp to ground
96
Speedometer sending unit feed
97
Tachometer sending unit feed
98
Interphone #8
99
Interphone #9
Wire Number
Circuit Description
100
Turret feed
101
Impulse relay feed (L terminal on impulse relay)
102
Large cal. gun firing solenoid to impulse relay (S terminal)
103
Small cal. gun firing solenoid to firing switch
104
Traverse motor feed
105
Recoil circuit on gyro control, through recoil switch
106
Gyro control (#3 on an connector) to motor stabilizer control,
yellow post
107
Gyro control (#1 on an connector) to motor stabilizer control,
green post
108
Stiffness circuit including disengage switch
109
Gyro stab. switch feed including circuit breaker and switch to
gyro motor or anti-backlash switch
110
Gun firing and lights, circuit breaker feed
111
Gun firing switch, feed from circuit breaker including safety
switch
112
Gun firing safety switch indicator light
113
Firing switch to large gun firing solenoid or impulse relay (F
terminal)
114
Gyro control resistors feed
115
Firing relay feed
116
Gyro indicator light feed
117
Positive lead to gun firing switches
119
Normally open side of anti-backlash switch, to circuit #107
120
Normally closed side of anti-backlash switch to gyro control
resistors feed
121
Junction of circuits #114 and 120 to gyro motor feed
122
Firing switch to loaders safety relay
123
Loaders safety relay to shell primer
124
Firing switches to selector switch
125
Feed to loaders trip button
126
Loaders trip button to feed on test relay
127
Test relay to loaders safety relay coil
128
Loaders trip button through loaders setting button to controlled
side of test relay
129
Loaders ready to fire indicator circuit
130
6.5 inch selector light
132
Ammunition hoist circuit
133
Parallel disconnect circuit
137
Outlet socket
138
Dome lamp, spot light and reel circuit
141
Interphone #1
142
Interphone #2
143
Interphone #3
144
Interphone #4
145
Interphone #5
146
12 Volt radio circuit
147
Light for periscope and sighting devices
148
24 Volt radio feed
149
Commanders master control circuit
151
Interphone #7
152
Commanders master control circuit feed
154
Rammer motor control circuit, including switch and indicator
155
Elevating motor feed through circuit breaker and main switch and
indicator ligh
156
Brake solenoid feed through brake relay
157
Elevating lead from reversing relay to elevating depressing
motor
158
Depressing lead from reversing relay to delevating depressing
motor
159
Turret vent fan
160
Interphone #6 (extra when used)
161
Feed for elevating and depressing control mechanism through
circuit breaker
162
Elevating relay control through control switch and limit
switch
163
Depressing relay control through control switch and limit
switch
164
Brake relay control through brake switch and ground
165
Elevating and depressing relay mechanism to ground
166
Automatic elevation control through resistor and limit
switch
167
Automatic depressing control through resistor and limit
switch
168
Equilibrator motor feed including switch and indicator light
169
Gun, How. firing area control circuit
173
Radio terminal box to ground
174
Rammer control circuit
198
Interphone #8
199
Interphone #9
Wire Number
Circuit Description
201
Generator field circuit
202
Generator armature circuit
203
Generator ground circuit
204
Generator regulator to ammeter or shunt
211
Right hand ignition switch feed
212
Right hand ignition switch RH coil
214
Starter switch or relay feed circuit
233
Temperature gauge to sending unit
234
Oil pressure pilot light
235
Water temperature pilot light
236
Oil pressure gauge to sending unit
255
Flame primer low tension circuit
256
Flame primer high tension circuit
267
Emergency stop switch
270
Regulator ground right hand
272
Transmission oil pressure pilot circuit light
274
Starter solenoid circuit right
280
Ignition coil to distributor
282
Starter motor feed right hand
293
Starter relay grounding circuit
294
Starter relay auxiliary grounding circuit
Wire Number
Circuit Description
300
Air pressure gauge to sending unit
301
Ignition switch to throttle solenoid through feed terminal in
terminal box
302
Throttle solenoid to throttle out switch (H)
303
Throttle out switch to brake throttle switch (A)
304
Feed terminal in terminal box to feed on clutch switch (D) and
normal range switch (E)
305
Normal range switch to low range (F) and high switches (G)
306
High range switch on low/high range shift to switch on
high/normal range shift switch (K)
307
Switch on high/normal range feeding direct solenoid and converter
solenoid
311
Brake governor switch (C) joining 312 to low side of
governor
312
Convertor solenoid to brake governor switch (C)
313
Common lead on brake governor switches to high side of
governor
314
Brake governor switch (B) to direct solenoid
315
Low range switch (F) on low/high range shift to high range
solenoid
316
High range solenoid ground
317
Clutch switch (D) to clutch solenoid
318
Clutch solenoid to clutch solenoid ground switch (J) on converter
direct shift
319
Common side of throttle cutoff switch and clutch grounding switch
to grounding terminal on terminal box
320
Brake throttle switch to grounding terminal on terminal box
321
Transmission lube pressure gauge circuit
324
Transmission temperature gauge circuit
325
Red flasher light with switch indicator and flasher
326
Differential low oil pressure warning light
327
Transmission high oil temperature warning light
329
Feed to transmission and steering control
330
Transmission high range control
331
Transmission low range control
332
Transmission reverse range control
333
Transmission clutch lockup control
334
Steer control right
335
Steer control left
336
Converter low oil pressure
337
Pilot control indicator circuit
338
Co-pilot control indicator circuit
339
Converter low lubricating oil pressure
340
Speed selector switches feed, pilot
341
Steer selector switches feed, pilot
342
Speed selector switches feed, co-pilot
343
Steer selector switches feed, co-pilot
344
Inlet fan, right
345
Inlet fan, left
346
Circulating fan, right
347
Circulating fan, left
Wire Number
Circuit Description
400
Heater feed
401
Heater starting switch to coil and indicator light
402
Heater starting switch to pump and solenoid valve
403
Running switch to thermal switch
404
Thermal switch to heater starting switch
405
Heater starting switch to motor and indicator light if used
406
Heater ignition circuit and indicator light if used
407
Heater in operating position indicator circuit
408
Oil heater circuit including indicator
409
Compartment heater circuit, including control unit
410
Safety valve reset circuit
411
Ventilation fan lead
412
Auxiliary generator transfer switch to battery heater and
indicator
413
Heater relay control circuit
414
Auxiliary generator voltage control reostat to voltage
regulator
415
Feed to special ventilating fan or rotoclone
416
Ground lead for special ventilating fan or rotoclone
417
Auxiliary shunt to auxiliary ammeter positive
418
Auxiliary shunt to auxiliary ammeter negative
419
Main feed to auxiliary control box
420
Auxiliary engine oil pressure gauge circuit
421
Auxiliary engine fuel cut off valve
422
Auxiliary engine magneto ground
423
Signal lamp auxiliary interphone
424
Field telephone auxiliary interphone
425
Field telephone auxiliary interphone
426
Ground auxiliary interphone
427
Tachometer, electric, "A" terminal, send to receive
428
Tachometer, electric, "B" terminal, send to receive
429
Tachometer, electric, "C" terminal, send to receive
430
Tachometer, electric, "D" terminal, send to receive
431
Speedometer, electric, "A" terminal, send to receive
432
Speedometer, electric, "B" terminal, send to receive
433
Speedometer, electric, "C" terminal, send to receive
434
Speedometer, electric, "D" terminal, send to receive
435
Rear door emergency warning light
436
Comp. feed including relay
437
Comp. relay control circuit including switch
450
Bilge pump switches feed and jumper between switches
451
Bilge pump switch to rear bilge pump
452
Bilge pump switch to front bilge pump
453
Ignition retard circuit, starter to solenoid through normally
closed switch
454
Ignition retard circuit, battery to normally open side of
switch
455
Two speed generator control circuit
456
Auxiliary generator disconnect control circuit including the
switch
457
Interphone #10
458
Engine fan clutch circuit
459
Control circuit for master relay and indicator light
459B
Master relay feed
460
Turn indicator circuit, right, front signal/marker lights
461
Turn indicator circuit, left, front signal/marker lights
462
Generator equalizer circuit, shunt type
463
Interphone #11
464
Interphone #12
465
Range finder feed
466
Range finder ground lead
467
Light switch to turn indicator switch feed
468
Bulldozer actuator armature feed
469
Bulldozer actuator field and clutch feed
470
Bulldozer control solenoid valve circuit
471
Winch control switch feed
472
Winch reverse solenoid circuit
473
Winch forward solenoid circuit
474
Front end fuel tank solenoid
475
Rear end fuel tank solenoid
476
Transmission fan clutch circuit
477
Differential filter pressure circuit
478
Generator equalizer circuit, interpole type
478A
Auxiliary generator equalizer circuit
478M
Main generator equalizer circuit
479
Battery heater control circuit
480
Wrecker solenoid valve control circuit
481
Magneto switch feed
482
Feed to auxiliary engine magneto grounding relay
483
Turn indicator, right blackout light
484
Turn indicator, left blackout light
485
Cab feed
486
Manifold heater, main engine
487
Manifold heater, auxiliary engine
488
Rectifier control to master relay circuit
489
Clearance lamp service feed
490
Clearance lamp blackout feed
491
Parking lights to light switch
492
Ignition ground, ground mag. switch
493
Auxiliary generator temperature indicator circuit
494
Engine decompression control circuit
495
Transmission oil level gauge circuit
496
Flood or spot lamp ground
497
Red flasher ground
Wire Number
Circuit Description
500
Three phase circuit lead "A"
501
Three phase circuit lead "B"
502
Three phase circuit lead "C"
503
Motor generator/alternator feed
504
Motor generator/alternator ground
505
Motor generator/alternator control box feed
506
Generator charge indicator circuit, left or main engine
