Keys to the 1986/1990 wiring diagram:
 
Cable colour codes. You may want to study this
 L/  light (in case of light green: stabilised power)   
 B  black (ground)  G  green (hot with ignition on, fused)
 K  pink (ballast terminal to ignition distributor)  N  brown (hot all the time, unfused)
 P  purple (hot all the time, fused)  R  red (accessories fed by sidelights switch)
 S  slate (=gray)(window motors)  U  blue (from main light switch via hand/dip switches)
 W  white (hot from ignition switch or starter solenoid, eventually ending on some ballast resistor)  Y  yellow (overdrive, injection, door locks,...)
  
Relays: W1-W2 is the switching current
C1-C2 is the power (switched) current; normally open; closes by energizing W1-W2
C3-C2 is the power (switched) current; normally closed; opens by energizing W1-W2
The drawing says C1/C2 even where C3/C2-type relays
are in use. Use the proper parts numbers!

As an aid in finding the various objects in the drawing, I have added coordinate values for each one. The coordinate system has its origin in the lower left corner of the drawing, and the values are Hor/Vert percentages. E.g. 50/50 is the centre of the drawing, and 100/75 is on the right side, ¾ up from the bottom.

#Hor%/Vert% Description
1:2/86   Battery Indicator
2:9/89   Alternator
3:22/91   Steering Lock Ignition Switch
4:24/94   Connector
5:21/87   Connector
6:17/84   Connector
7:24/84   Connector
8:41/92   Red Ident
9:43/92   Ignition Switch Relay
10:10/69   Starter Motor & Solenoid Switch
11:18/69   Terminal Post
12:22/69   12 Volt Battery
13:13/62   Transmission Light-In Gear Selector
14:26/62   4 Position Lighting Switch
15:4/58   Dim/Dip Relay (UK only)
15a:4/58   Relay ??
16:13/61   Dim/Dip Fuse (UK only)
17:18/45   Power Resistor (Dim/Dip UK only)
18:11/60   Pektron Diode (Dim/Dip UK only)
19:13/55   Main Beam Warning Light
20:13/51   R.H. Headlamp Main Beam
21:13/48   R.H. Headlamp Main Beam
22:13/44   L.H. Headlamp Main Beam
23:13/41   L.H. Headlamp Main Beam
24:13/37   R.H. Headlamp Dip Beam
25:13/34   L.H. Headlamp Dip Beam
26:21/43   Fuse Unit no. 1
27:24/38   Headlamp Relay
28:26/42   Headlamp Main Beam Flash Switch (Incorporate with Indication Stick)
29:21/35   Fuse Unit no. 2
30:29/35   Fuse Unit no. 6
31:13/30   R.H. Side Lamp
32:13/26   L.H. Side Lamp
33:13/23   R.H. Tail Lamp
34:13/19   L.H. Tail Lamp
35:13/16   Number Plate Lamp
36:13/12   Panel Edge Light
37:13/8   Panel Edge Light
38:13/5   Panel Edge Light
39:13/2   Panel Light
40:21/13   Panel Light Switch
41:27/9   Panel Light
42:27/5   Panel Light
43:27/2   Panel Light
44:39/23   Sidelamp Warning Light (Italian Models only)
45:39/20   R.H. Fog Lamp (Optional)
46:39/16   L.H. Fog Lamp (Optional)
47:39/14   Heater Control Button Lights
48:39/10   Panel Light
49:39/7   Panel Light
50:39/5   Panel Light
51:39/2   Panel Light
52:44/85   Fuse Unit no. 7
53:47/85   Fuse Unit no. 5
54:33/80   Clock
55:40/80   Cigar Lighter & Switch
56:50/78   Horns
57:53/76   Horn Relay
58:56/77   Horn Push
59:56/75   Horn Slip Ring Lower Steering Column
60:33/69   Fuse
61:36/69   Fascia Radio (Optional)
62:36/64   Front Interior Light Switch
63:36/62   Front Interior Lamp
64:36/59   L.H. Front Door Switch
65:41/59   R.H. Front Door Switch
66:34/55   L.H. Rear Interior Lamp
67:41/55   R.H. Rear Interior Lamp
68:37/53   L.H. 2 Way Switch in rear arm rest
69:41/53   R.H. 2 Way Switch in rear arm rest
70:34/50   L.H. Rear Door Switch
71:39/50   R.H. Rear Door Switch
72:36/48   L.H. Courtesy Light
73:39/48   R.H. Courtesy Light
74:42/46   Rear Radio Feed
75:35/44   L.H. Cigar Lighter
76:40/44   R.H. Cigar Lighter
77:41/40   Relay (Isolation Windows)
78:36/40   Otter Switch (Thermal)
79:38/36   R.H. Front Window Lift Switch (L.H. on L.H.D.)
80:41/36   R.H. Front Window Lift Motor (L.H. on L.H.D.)
81:38/33   L.H. Front Window Lift Switch (R.H. on L.H.D.)
82:41/33   L.H. Front Window Lift Motor (R.H. on L.H.D.)
83:47/68   Otter Switch (Thermal)
84:53/68   Relay (Window Isolation)
85:57/69   To Item 100 (when have Division & no Elec Windows)
86:50/62   L.H. Front Window Lift Switch (R.H. on L.H.D.)
87:55/62   L.H. Front Window Lift Motor (R.H. on L.H.D.)
88:51/59   R.H. Rear Window Lift Switch
89:55/58   R.H. Rear Window Lift Motor
90:50/52   Front Elec. Division Window Lift Switch
91:49/42   L.H. Rear Elec. Division Window Lift Switch
92:53/42   Elec. Division Window Lift Motor
93:51/32   R.H. Rear Elec. Division Window Lift Switch
94:53/25   Division Isolation Relay
95:49/25   Otter Switch (Thermal)
96:51/18   Front Switch
97:55/18   Electric Division Motor
98:51/13   L.H. Rear Switch
99:51/8   R.H. Rear Switch
100:46/28   Electric Division Only
101:61/90   Ignition Warning Light
102:63/86   Wiper Switch - Lucas No. 39944A
103:68/86   Wiper Motor 14W
104:74/85   Fuse Unit no. 8
105:75/85   Fuse Unit no. 3
106:63/77   Screen Jet Motor
107:68/76   Screen Jet Switch
108:63/73   R.H. Fuel Pump
109:63/69   L.H. Fuel Pump
110:63/66   L.H. Fuel Tank Unit
111:63/62   R.H. Fuel Tank Unit
112:70/65   Fuel Tank Changeover Switch
113:67/59   Fuel Gauge
114:64/55   Water Temperature Unit
115:67/55   Water Temperature Gauge
116:65/52   Oil Pressure Unit
117:71/52   Oil Pressure Gauge
118:64/48   L.H. Stop Lamp
119:63/45   R.H. Stop Lamp
120:73/45   Stop Lamp Switch - Hydraulic Switch in Brake Line
121:64/41   Kick Down On Gearbox
122:72/41   Kick Down Switch
123:83/93   Fuse Unit no. 4
124:85/89   Ignition Coil
125:90/84   Distributor
126:84/80   Handbrake Warning Light
127:84/76   Handbrake Warning Light Switch
128:90/76   Brake Fluid Level Switch
129:81/73   In-Line Fuse
130:82/72   Green Ident
131:82/68   Green Ident
132:83/68   Rear Window Switch
133:88/65   Relay Incorporating Resistance
134:82/65   Warning Light
135:93/73   Rear Window Heater
136:91/62   Choke Warning Light
137:93/62   Manual Choke Switch
138:97/60   Gearbox Transducer (GM400)
139:81/60   Elec. Speedometer
140:83/53   Low Coolant Warning Light
141:89/53   Low Coolant Unit
142:94/53   Coolant Sensor
143:84/48   R.H. Reverse Light
144:84/45   L.H. Reverse Light
145:84/38   Tachometer
146:71/31   Automatic Transmission and Reverse Light Switches
147:95/32   Starter Inhibit Relay
148:64/23   R.H. Heater Motor
149:64/20   L.H. Heater Motor
150:75/22   Heater Motor Switch
151:97/9   Hazard Warning System (Optional Extra)
152:84/23   In-Line Fuse
153:87/22   Hazard Flasher
154:95/22   Hazard Pilot Bulb
155:87/14   Hazard Switch
156:77/14   Flasher Unit
157:73/12   R.H. Flasher Warning Light
158:64/12   R.H. Front Flasher
159:64/9   R.H. Rear Flasher
160:64/5   L.H. Rear Flasher
161:64/2   L.H. Front Flasher
162:75/7   Flasher Switch
163:73/2   L.H. Flasher Warning Light
 
Numbers 164-185 are on the separate Airco drawing:
164:    Rear Air Conditioning
165:    To Ignition Switch
166:    Rear Air Con Fan Relay
167:    35A Fuse (50A when Refrigerated Cool Box Fitted)
168:    To Socket for Refrigerated Cool Box
169:    Air Con Relay
170:    Speed Resistor
171:    Radio Suppressors (1 micro F.)
172:    Fan Motor
173:    Fan Motor
174:    N.S. Arm Rest
175:    On/Off and 3 Speed Fan Blower Switch
176:    Thermal Switch
177:    Front Air Conditioning
178:    To Compressor Clutch/Fan Relay
179:    Compressor Clutch
180:    'Pektron' Diode
181:    Solenoid Valve Assembly
182:    30 Amp In Line Fuse
183:    Air Conditioning Unit
184:    Thermostat Switch
185:    Fan Motor Switch
 
Numbers 186-197 are on the separate Cooling drawing:
186:    Cooling Circuit
187:    Alternator Feed
188:    85A Fuse
189:    85A Fuse
190:    O.S. Cooling Fan Relay
191:    O.S. Cooling Fan
192:    Link to 178
193:    N.S. Cooling Fan Relay
194:    N.S. Cooling Fan
195:    Radiator Sensor
196:    'Pektron' Diode & Radiator Sensor Relay
197:    To Horn Relay Ignition Feed