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.
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].
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 |
| 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 |
| 507 |
Generator charge indicator circuit, right engine |
| 508 |
Generator charge indicator circuit, auxiliary engine |
| 509 |
Warning light circuit, selective warning system |
| 511 |
Battery heater feed, from engine generator to series paralleling
switch |
| 512 |
Battery heater feed, battery heaters in parallel |
| 513 |
Battery heater feed, battery heaters in series |
| 514 |
Dimmer switch to blackout upper beam (IR) |
| 515 |
Dimmer switch to blackout lower beam (IR) |
| 516 |
Power pack feed (IR) |
| 517 |
Periscope feed (IR) |
| 518 |
Flood or work lamp feed |
| 519 |
High beam indicator circuit |
| 520 |
Main light switch to IR BOD selector |
| 550 |
Power feed to pulsing relay box |
| 551 |
Traverse lead between cont. potentiometer wiper and relay
contacts |
| 552 |
Traverse center tap on cont. handle potentiometer to deat spot
res. |
| 553 |
Elevation center tap on cont. handle potentiometer to deat spot
res. |
| 554 |
Elevation lead between cont. potentiometer wiper and relay
contacts |
| 555 |
Common ground in pulsing relay system |
| 567A |
Voltmeter from ignition switch |
| 568 |
Alternator field from ignition switch |
| Wire Number |
Circuit Description |
| 600 |
Elevation tracking motor feed |
| 601 |
Tracking motor elevating circuit |
| 602 |
Tracking motor depressing circuit |
| 603 |
Elevation gyro gauge circuit |
| 604 |
Elevation gyro motor and pickoff motor feed |
| 605 |
Elevating electrodyne feed |
| 606 |
Elevating electrodyne circuit |
| 607 |
Depressing electrodyne circuit |
| 608 |
Traverse tracking motor feed |
| 609 |
Tracking motor left traversing circuit |
| 610 |
Tracking motor right traversing circuit |
| 611 |
Traverse gyro gauge circuit |
| 612 |
Traverse gyro motor and pickoff motor feed |
| 613 |
Left traversing electrodyne circuit |
| 614 |
Right traversing electrodyne circuit |
| 615 |
Traversing electrodyne feed |
| 616 |
Hydraulic valve circuit |
| 617 |
Loaders traverse safety lamp feed |
| 618 |
Delay relay coil circuit |
| 619 |
Thermo delay switch actuating circuit |
| 620 |
Delay relay holding circuit |
| 621 |
Gunners handle pickoff motor feed |
| 622 |
Commanders handle pickoff motor feed |
| 623 |
Commanders override circuit |
| 624 |
Commanders override switch feed |
| 625 |
Main positive feed to turret control box |
| 630 |
Delay circuit feed |
| 631 |
Safety lamp return |
| 632 |
Loaders safety switch and safety lamp feed |
| 633 |
Loaders safety relay coil circuit |
| 640 |
Auxiliary generator decompression circuit |
| 641 |
Booster motor control |
| 642 |
Booster motor power |
| 643 |
Inverter feed |
| 644 |
Inverter ground |
