Extract from MGA Newsletter in Safety Fast!
MGA Wiring Loom
Do you have trouble reading circuit diagrams or do you find it difficult tracing electrical problems when working on your car with the workshop manual perched precariously somewhere and about to fall off? If so, then John Barrett has come up with the answer by producing for the register a simple guide to cable colours and what is connected to each end which I reproduce below.
1 Blue - light switch "S2" to dipper switch.
2 Blue with red - dipper switch to LHS & RHS dipped headlamps.
4 Blue with white - dipper switch to LHS & RHS headlights, full beam.
9 White (via ignition, not fused)
- ignition switch to petrol pump via fuse unit terminal "A3".
- ignition switch to coil "SW" via fuse unit terminal "A3".
- ignition switch to ignition warning light.
14 White with purple - LHS rear indicator lamp to terminal "7" on
direction indicator relay box.
15 White with brown - RHS rear indicator lamp to terminal "3" on the
direction indicator relay box.
16 White with black - coil "CB" to distributor.
17 Green (via ignition, fused)
- fuse unit "A4" to direction indicator flasher unit.
- fuse unit "A4" to stop lamp switch.
- fuse unit "A4" to windscreen wiper motor.
- fuse unit "A4" to terminal "B" on fuel gauge.
- "B" terminal on fuel gauge to heater fan switch.
- "B" terminal on fuel gauge to direction indicator switch.
18 Green with red - LHS front indicator to indicator flasher unit
terminal "6".
19 Green with yellow - direction indicator switch to indicator relay
unit terminal "4".
20 Green with blue - direction indicator switch to indicator relay
unit terminal "8".
21 Green with white - RHS front indicator to indicator flasher unit
terminal "2".
22 Green with purple - hydraulic stop lamp switch to indicator relay
unit terminal "5".
23 Green with brown
- heater fan switch to fan motor.
- direction indicator flasher unit terminal "L" to direction indicator relay
unit terminal "1".
24 Green with black - petrol gauge terminal "T" to petrol tank.
25 Yellow
- control box terminal "D" to dynamo terminal "D".
- control box terminal "D" to ignition warning light.
29 Yellow with green - control box terminal "F" to dynamo terminal
"F".
33 Brown (always live, not fused)
- control box terminal "A" to fuse unit terminal "A1".
- starter switch to control box terminal "A".
36 Brown with blue
- ignition switch to control box terminal "A1".
- ignition switch to lightning switch terminal "A".
38 Brown with green
- fuse unit terminal "A2" to horn.
- RHS horn to LHS horn.
40 Brown with black
- RHS horn to LHS horn.
- RHS horn to horn push.
41 Red
- lightning switch terminal "S1" to map light switch.
- lightning switch terminal "S1" to panel light rheostat.
- lightning switch terminal "S1" to LHS & RHS front side lamps.
- lightning switch terminal "S1" to LHS & RHS rear tail lamps.
- lightning switch terminal "S1" to fog lamp switch.
- map light switch to map light.
42 Red with yellow - fog lamp switch to fog lamp.
44 Red with white
- rheostat to panel light.
- rheostat to speedometer.
- rheostat to dual gauge.
- rheostat to fuel gauge.
57 Black
- number plate light and all rear lamps to chassis by RHS shock absorber.
- all front lights to chassis by bonnet release mechanism cross member.
- heater fan to chassis by RH inside engine bay/wheel arch.
- control box terminal "E" to chassis by RH inside engine bay/wheel arch.
- dual gauge to chassis by RH engine bay/wheel arch.
- petrol gauge to petrol gauge.
- petrol gauge to windscreen wiper switch.
- petrol gauge to horn push.
- dual gauge to rev counter.
- rev counter to speedometer.
62 Black with green - windscreen wiper switch to wiper motor.
66 Light green - direction indicator flasher unit terminal "P" to
direction indicator warning light.
U Blue - light switch "S2" to dipper switch.
UR Blue with red - dipper switch to KHS & RHS dipped headlamps.
UW Blue with white
- dipper switch to LHS & RHS headlamps, full beam.
- dipper switch to main beam warning light.
- LH headlamp main beam connector to headlamp flick relay terminal "C2", if
fitted.
W White (via ignition switch, not fused)
- ignition switch to fuse unit terminal "A3".
- fuse unit terminal "A3" to coil "SW".
- fuse unit terminal "A3" to ignition warning light.
WB White with black - coil "CB" to distributor.
G Green (via ignition, fused)
- fuse unit "A4" to direction indicator flasher unit terminal "B".
- fuse unit "A4" to stop lamp switch.
- fuse unit "A4" to windscreen wiper motor terminal "2".
- fuse unit "A4" to terminal "B" on fuel gauge.
- terminal "B" on fuel gauge to heater fan switch.
GR Green with red - LHS front and rear indicator to flasher unit.
GW Green with white - RHS front and rear indicator to flasher unit.
GP Green with purple - hydraulic stop lamp switch to LH & RH stop
lamps.
GN Green with brown
- heater fan switch to fan motor.
- flasher unit terminal "L" to flasher switch.
GB Green with black - petrol gauge terminal "T" to petrol tank unit.
Y Yellow
- control box terminal "D" to dynamo terminal "D".
- control box terminal "D" to ignition warning light.
YG Yellow and green - control box terminal "F" to dynamo terminal
"F".
N Brown (always live, not fused)
- starter switch to control box terminal "A".
- control box terminal "A" to fuse unit terminal "B".
NU Brown with blue
- ignition switch to control box terminal "A1".
- ignition switch to lighting switch terminal "A".
NG Brown with green
- fuse unit terminal "A2" to horn.
- RHS horn to LHS horn.
NB Brown with black
- RHS horn to LHS horn.
- RHS horn to horn push.
R Red
- lightning switch terminal "S1" to map light switch.
- lightning switch terminal "S1" to panel light rheostat.
- lightning switch terminal "S1" to LHS & RHS front sidelamps.
- lightning switch terminal "S1" to LHS & RHS rear tail lamps.
- lightning switch terminal "S1" to number plate light.
- lightning switch terminal "S1" flog lamp switch.
- map light switch to map light.
RY Red with yellow
- fog lamp switch to fog lamp.
- LHS fog lamp to RHS fog lamp, it fitted.
RW Red with white
- rheostat to rev counter panel lamp.
- rheostat to speedometer panel lamp.
- rheostat to dual gauge panel lamp.
- rheostat to fuel gauge panel lamp.
B Black
- number plate & all rear lamps to chassis by RH rear shock absorber.
- all front lights to chassis by bonnet release mechanism cross member.
- heater fan to chassis by RH inside engine bay/wheel arch.
- control box terminal "E" to chassis by RH inside engine bay/wheel arch.
- dual gauge to chassis by RH inside engine bay/wheel arch.
- control box terminal "E" to to windscreen wiper motor.
- dual gauge to petrol gauge.
- petrol gauge to windscreen wiper switch.
- petrol gauge to horn push.
- dual gauge to rev counter.
- rev counter to speedometer.
BG Black with green
- windscreen wiper switch to wiper motor.
LG Light green
- direction indicator flasher unit terminal "P" to direction indicator
warning light.
Note: when a cable has two code letters, the first denotes the main colour and the second denotes the tracer colour.