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Fiat X1/9 Interactive Wiring Diagram

The 1979 Australian factory wiring sheet, fully traced. Tap any component, fuse or single wire and its whole circuit lights up in the real cable colours, back to the fuse box.

Wiring sheet 1979 Australia
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Tap a part to light its whole circuit Tap one wire to follow just that conductor Hover a number to see what it is Operate works the switches and relays

About this diagram

This is the Fiat factory wiring diagram for the 1979 Australian-market X1/9, print 503.553, a supplement to service manual 503.552. Every wire on the sheet has been traced by hand and saved, so tapping a part needs no guesswork: the whole circuit lights at once, in the cable colours from the sheet's own key.

The three grey vertical strips are the sheet's continuation numbers. A wire that stops at a number resumes at the matching number elsewhere on the page, and the viewer follows those jumps for you. Runs hidden inside the striped harness bundles are drawn as solid lines of the same colour, matched by cable colour at each end of the loom.

Circuits you can trace

29 circuits are traced, 351 wire sections in all, with 15 of them wired up as working switch models you can operate. Every numbered continuation printed on the sheet is covered.

All 29 circuits, and what each one does
  • Headlights: switch 46, dip lever 55, relays 26 and 25, both lamps 3 Switch 46 pin H sends V through loom B to the dip lever 55. Low beam: HR to fuse pin 5, bus 5-6, fuses E and F, HN and H to both lamps. High beam: L through the diode, LR through loom B to relay 26; relay 26 passes battery M from fuse pin 10 as L to fuse pin 3, bus 3-4, fuses C and D, VN and V to both lamps and to the panel for indicator 41. The lighting switch itself is fed from fuse pin 15 through relay 25's rest contact.
  • Parking, tail and plate lamps: switch 46, fuses G and H Battery from the fuse box 9/10 bus reaches switch 46 pin O by a white (B) wire via pin 2. In both lit positions the switch feeds pin I, an AR wire to the 7/8 bus. Fuse H: GR to loom 2 and to the front-top parking lamp (210/3); out of loom 2 at 359 to the bottom tail lamp 88, and on by a second GR (390/419) to the upper plate lamp. Fuse G: GN to panel connector 28 pin 3 (indicator 42 and, by GN 294/72, the front-bottom parking lamp) and GN 223/88 through loom 2 to the lower plate lamp, then on (416/432) to the top tail lamp. Plate lamps earth by NZ 418/398 to an earth star.
  • Pop-up headlamp motors 11, relays 4, limit switches 12 Each motor is fed V from its relay 4 pin 30 and VB from fuse Q; its N and H lines go to the relay coil (HN) and to fuse R (HG). The relays' 87 contacts take AB/A from fuses I and L. Both motors and both limit switches earth at the earth stars.
  • Right-hand turn signals: lamp 87 back to the fuse box From the top-right rear lamp 87: A wire 434/357 to a connector, back through loom 2 to hazard switch pin L (213/370), then pin L's other wire 369/244 through loom 1 to the turn-signal lever 56. The lever common (Z) runs through loom 1 to hazard pin H (243/368), Z 138/367 to the flasher 20, B 137/377 from the flasher + back to hazard pin D, T to D closed when the hazard is off, C 76/376 to fuse box pin A. The same A net also feeds the front lamp 1 and side marker 13 (245/2) and hazard pin L (244/369, 213/370).
  • Left-hand turn signals: lamp 87 (bottom-right) back to the fuse box From the bottom-right rear lamp 87: AN wire 386/356 to a connector, back through loom 2 to hazard switch pin I (214/372), then pin I's other wire 371/242 through loom 1 to the turn-signal lever 56 contact e. The lever common (Z) runs through loom 1 to hazard pin H, flasher 20, hazard pin D to T, C 76/376 to fuse box pin A. The AN net also feeds the front-left lamp 1 and side marker 13 (241/73) and hazard pin I (242/371, 214/372).
  • Stop lamps: switch 19 to both lamps 89 Fuse box pin A → C 76/376 → hazard switch pin T → C 135/375 → stop-light switch 19. Pressing the pedal sends R 134/212 through loom 2 to 358/388 and the bottom cluster's stop lamp 89, with a second R wire (387/433) on to the top cluster's stop lamp. The switch's supply terminal also feeds C 136/206 up to the instrument panel.
  • Back-up lamps: switch 53 to both lamps 90 Orange (C) supply from a connector pin via 349/329 to the 2-pin connector at switch 53 (a branch 330/430 also feeds electrovalve 69). Switch output B via 331/392 to the bottom-right lamp 90, chained by 391/431 to the top-right lamp 90. Each lamp earths through an N loop to the earth symbol in its cluster.
  • Horn: button 57, relay 7, both horns 5 Fused Z supply (96/41) to relay 7 pins 85 and 30. The button 57 earths the coil through pin 86 (HN 42/238 via loom 1). When the coil pulls in, 30 to 87 closes and A 40/54 feeds the lower horn, with a second A wire (53/23) on to the upper horn. Each horn earths at its own symbol.
  • Wipers and washer: lever 47, interrupter 15, motor 22, pump 21 The lever's wires drop through the reroute block to a connector row and into loom T, which exits at strip 2 rows 253-261 for the motor and the interrupter. The supply is an orange (C) wire from strip 2 row 300/240 through loom 1 to a connector pin and along a bar to the lever. Wash: VN from the lever runs right to a pin beside the horn button's, down through loom 1 to row 239 and the pump. The motor earths at the top earth star (151/308), the pump at the lower star (145/33).
  • Heater fan: switch 60, motor 61 The C net from the stop-light switch's supply terminal (136/206) climbs the panel wire column to switch 60. The switch feeds the motor's AN or R connection; the motor earths at its own symbol. The same C pin also feeds switch 65 (205/198) and, from 65's pin, the ideogram lamp 63.
  • Rear window demister: switch 65, relay 17, element 73 Switch 65 joins the C net to CB 197/126, relay 17's coil. The coil returns through the relay N chain. Contacts: fuse M (R 93/123) to pin 87, M 233/127 through loom 2 to the ring block and strip 3 row 338 = 409, up to the element 73, which earths at its own symbol. A second M (270/128) goes to the panel for indicator 35.
  • Radiator fan: thermostatic switch 6, relay 8, motor 10 Relay 8's coil is fed from fuse box pin 1 (AN 168/47) and earthed by the thermostatic switch 6 (BN 24/45, N 32/25). Its contacts pass fuse N (Z 95/48) to the motor 10 (A 51/44), which earths at the lower star (N 35/52). Pin 85 also carries S 229 through loom 2 to strip 3 row 342 = 407 (not followed).
  • Carburettor fan: switch 74, relay 75, motor 86 Fuse A's A 79/231 runs through loom 2 to strip 3 340/394 and relay 75's 30/85. The thermostatic switch 74 earths the coil (HR, NZ 399/395); the contacts pass R to the motor 86.
  • Fast idle: electrovalve 69, switches 52, 70, 72 The valve is fed C from the back-up switch's net (330/430) and earthed via the 3rd/4th gear switch 72 and clutch switch 52 in series (BN 424/429, 423/327, NZ 397/328) or via the control switch 70 (NZ 396/428) to earth star 3.
  • Ignition, starter and charging: switch 45, starter 81, alternator 78, regulator 84, coil 82 Battery M reaches the ignition switch pin 30 through the instrument-panel loom (111/266). On: 15/54 sends AN through the loom to fuse box pin 1 (264/167) and the panel (265/281). Start: 50 sends R through the panel loom, loom 2 and the ring block to strip 3 341/412 and the starter solenoid; RV (262/121) energises relay 16 for the brake-fluid lamp test. The starter's main terminal 30 carries the battery cable (108/411) and the alternator's B+ cable (405/410). The alternator's D+ (NZ) runs into loom 2 for the charge indicator; R, V and N go to the regulator 84. The coil 82 is fed by B+ (battery symbol) and feeds the idle-stop solenoid 85 (408/393).
  • Gauges and senders: 76, 79, 80, fuel sender 51 The three engine senders feed VB/HN/HG wires to strip 3, the ring block and loom 2, out at strip 2 rows 220/232/218 to the panel connectors 28. The fuel sender's RN and AG take the same path to the 8-pin connector; its NZ earths at star 3.
  • Tachometer signal: coil 82 to connector 28 The coil's MB terminal runs to strip 3 (406/353), through loom 2, out at strip 2 row 217 and by 217/291 to the 8-pin panel connector for the tachometer 40.
  • Panel lamps: switch 59, ballasts 58, lamp 62 The two M columns from strip 2 feed switch 59; BR goes through the ballast resistors 58 and AB directly to the AB bus (panel lamps 29 beyond, not drawn). Lamp 62 is fed from the C net through an inline connector and earths on the panel N column.
  • Cigar lighter 64 and clock connector 27 ZB 201/195 feeds the element; Z joins the clock connector pin 4 (200/296); the housing lamp GN joins the parking illumination net inside loom 2 (199/222); N 203/312 earths at the top star, together with the relay N chain.
  • Courtesy light 68 and jamb switches 49 ZB 336 feeds the lamp (the feed's far end is not drawn). The lamp's switch earths through NZ 400 to star 3 directly, or through N 362/343, loom 2, 228/380 to the bottom jamb switch; the top jamb switch is linked by N 321/381.
  • Handbrake warning: switch 54, flasher 18 Switch 54 earths BN 337 through loom 2 to the flasher 18's + terminal; the flasher is fed C from fuse B (78/131) and drives AB 129/273 to the panel connector for lamp 32.
  • Brake fluid warning: float switch 9, relay 16 Relay 16 (coil RV 121/262 from the ignition switch's start position) pulls pin 30 to N as a lamp test; BN 283/122 reaches the tilted panel connector. The float switch 9 earths the same connector pin through AB 49/282 and an inline connector; its N 50/313 goes to the top earth star.
  • Radio harness 48 and speaker harness 50 Battery RV 109/316 and five other wires rise to strip 3 rows 315-320; AR and BR continue through loom 2 (227/226 → 344/345) to the speaker harness 50.
  • Aerial motor: switch harness 66 to motor harness 71 (LR) LR from the switch harness 66 pin T runs along the bottom to strip 2 row 196, jumps to strip 3 row 363, passes through the ring block and loom 2 to row 364 and then 364/425 to the motor harness 71.
  • Inline fuse 23: battery M from fuse pin 14, Z out Battery M reaches fuse box pin 14 and, by the 156/101 pair, the inline fuse 23; its Z output runs to strip 2 and jumps 152/236 into the looms. The key lists fuse 23 as protecting the clock, radio, hazard and courtesy circuits.
  • Relay earth chain The coil returns of relays 26, 17, 16, 25 and both relays 4 are daisy-chained by N wires (177/125, 124/117, 120/171, 170/18, 21/57, 60/202) ending at a connector ring beside the cigar lighter.
  • Battery M feed and block branches Brown (M) lead from battery positive to the small block, then four branches: 109/316, 110/158, 111/266, 112/157.
  • Battery to starter cable 108/411 Battery positive to starter motor terminal 30. One cable, two drawn outlines.
  • Aerial harness wire 366 (AB) Component 66 terminal U to component 71 via 194/366 and 365/426.

Cable colour codes

A light blue, B white, C orange, G yellow, H grey, L blue, M brown, N black, R red, S pink, V green, Z violet. A two-letter code is the first colour with a tracer of the second.

What is read from the sheet, and what is not

Everything here is read from the printed sheet. Fiat did not draw the fuse box internals, so the links from a fuse position to its pin are shown as stated assumptions, and switch behaviour is inferred from the drawn contacts and the component key rather than from factory contact tables. Check against your own car before relying on it for repairs.

Source: original 1979 Australian Fiat X1/9 wiring diagram, page 3, 4657 × 3109 px. Component names from the page 2 key. Looking for the scanned originals or another model year? They are in the Technical Library.