Mgb Electrical Systems

by Astley, Rick

• ISBN13: 9781845840570
• ISBN10: 1845840577
• Format: Paperback
• Copyright: 2006-10-15
• Publisher: Veloce

Summary

This book is essential reading for every MGB enthusiast. The mechanical aspects and the restoration of the vehicle have been written about in numerous publications but the so often maligned electrical system has never before been comprehensively covered. For those new to vehicle electrical systems the book provides a simple primer using mechanical analogies. Each system in the car has its own chapter, with simple and uncluttered circuit diagrams in which each wire can be seen in its real colors. More than a how-to guide, the book also explains the ""why"" of each system and procedure, aiding diagnostics when things don't go quite as they should. The many fault finding guides help pin those elusive problems down. For those wishing to improve the car for reliability and safety reasons, there are lots of tips and fun-to-do projects.

Author Biography

Rick Astley is a dual British-Canadian citizen living in the USA. An electrical engineer, he was educated in Britain. He currently works as the Automotive Applications Manager for a Silicon Valley company. This work has entailed his being embedded with the electrical architecture group of one of the Big 3 car makers where he was able to observe first hand the process behind the design of a vehicle’s electrical system. He lives with his wife Anne, a 1970 MGB roadster and a 1970 MGB-GT V8 conversion, all reside in Farmington Hill, Michigan.  He has two grown sons.

Table of Contents

Acknowledgements & about the author	7	(1)
Foreword	8	(1)
Safety first	9	(2)
General	9	(1)
Electric shock	9	(1)
Heat burns	9	(1)
Acid burns	9	(1)
Fire	10	(1)
Toxic gas	10	(1)
Tools, wire handling & connectors	11	(6)
Tools	11	(1)
Screwdrivers	11	(1)
Safety	11	(1)
Blade drivers	11	(1)
Phillips (crosspoint)	11	(1)
Pozidrive®	11	(1)
Precision screwdrivers	11	(1)
Circuit tester	11	(1)
Multimeter	12	(1)
Wire handling	12	(1)
Automotive wire	12	(1)
Jumper wires	13	(1)
Connectors	13	(3)
Connector terminals	13	(1)
Bullet connectors	13	(1)
Soldering bullet connectors	13	(1)
Blade connectors	13	(1)
Crimping blade connectors	14	(1)
Piggyback connectors	15	(1)
Earthing connectors	15	(1)
Splicing connectors	15	(1)
IDC taps	16	(1)
Tape	16	(1)
Heat shrink tubing	16	(1)
Basic electrical theory	17	(4)
Electrical units	17	(1)
Volt	17	(1)
Amp	17	(1)
Watt	17	(1)
Ohm	17	(1)
Other electrical units	17	(1)
Some useful formulae	18	(1)
A practical exercise	18	(1)
Corrosion	18	(3)
Atmospheric corrosion	19	(1)
Galvanic corrosion	19	(2)
Emergency repairs	21	(4)
General	21	(1)
What to carry	21	(1)
Mobile phone	21	(1)
Jump start cables	21	(1)
Fan belt	21	(1)
Fuses	21	(1)
Spark plugs	21	(1)
Bulbs	21	(1)
Wire	21	(1)
PVC adhesive electrical tape	22	(1)
Torch (flashlight) and plug-in light	22	(1)
Water repellent	22	(1)
Rain-X®	22	(1)
Tools	22	(1)
Running repairs	22	(1)
Battery/generator problems	22	(1)
Ignition problems	22	(1)
High tension wires	22	(1)
Checking for a spark	23	(1)
Poor connections	23	(1)
Blade and bullet connectors	23	(1)
Switch contacts	23	(1)
Ignition switch	23	(1)
Fuel pump	24	(1)
Sealed beam units	24	(1)
Poor earths	24	(1)
Joining wires	24	(1)
Sneak currents	25	(3)
What are sneak currents?	25	(1)
Sneak example	25	(1)
MGB sneak currents	26	(2)
Stop/tail lamps	26	(1)
Stop/tail circuit	26	(1)
Engine run-on	26	(1)
Unintended engine starting	27	(1)
Engine earth/ground strap	27	(1)
Wire harness	28	(12)
Wires & components	28	(1)
Wire colours	28	(1)
Component codes	28	(1)
Major harnesses	29	(1)
MGB wire function finder	30	(7)
Component codes	37	(2)
Wire sizes	39	(1)
Fusing & fuses	40	(7)
Fuse technology	40	(1)
Fusing architecture	40	(1)
Fuse rating	40	(1)
MGB fuses	41	(2)
The fuse block	41	(1)
Fuse values	42	(1)
Line fuses	42	(1)
Blown fuses	42	(1)
Adding additional fuses	43	(1)
Selecting a fuse value and wire size	43	(1)
Fuse types	44	(1)
Fuse-holders	44	(3)
Circuit-breakers	45	(1)
PolySwitch® polymer PTCs	46	(1)
Battery	47	(9)
Battery ratings	47	(1)
Ampere hours (Ah)	47	(1)
Reserve capacity (RC)	47	(1)
Cold cranking amps (CCA)	47	(1)
Cranking amps (CA)	47	(1)
Battery size	48	(1)
Group size	48	(1)
Battery charging	48	(1)
Charging methods	48	(1)
Battery discharge	48	(1)
Battery problems	49	(1)
Temperature effects	49	(1)
Battery testing & maintenance	49	(2)
Battery connections	49	(1)
Electrolyte	49	(1)
No load voltage	50	(1)
Load testing	50	(1)
Jump starting	51	(1)
Connections for cars of like polarity	51	(1)
Connections for cars of unlike polarity	51	(1)
Starting the car	51	(1)
Dual to single battery conversion	51	(1)
Battery selection	51	(1)
Battery choice	51	(1)
Fitting the battery	52	(1)
Why batteries fail	52	(1)
Adding a battery disconnect switch	52	(2)
Why add a disconnect switch?	52	(1)
Radio memory and clock problems	52	(1)
Switch selection	53	(1)
Earth switching	53	(1)
Schematic	54	(1)
Earth connection	54	(1)
Installing the switch	54	(1)
Attaching the cables	54	(1)
Cut-off switch diagnostics	54	(1)
Adding a radio memory & clock maintainer	54	(1)
Battery system fault finding	55	(1)
Charging system	56	(20)
Motor & generators	56	(1)
Isolate the problem	57	(1)
The dynamo	58	(3)
Checking the system	58	(1)
Dynamo service	59	(1)
Disassembly	59	(1)
The armature	59	(1)
The field coils	59	(1)
The commutator	60	(1)
The brushes	60	(1)
Re-assembly	60	(1)
Body and end plates	60	(1)
The dynamo control box	61	(3)
Description	61	(1)
Service	62	(1)
Identification	62	(1)
Maintenance	62	(1)
Adjustment	62	(1)
Checking the ignition warning lamp	63	(1)
The dynamo charging circuit	63	(1)
Dynamo circuit fault finding	64	(1)
The alternator	64	(5)
Description	64	(2)
Checking the ignition warning lamp	66	(1)
Testing the alternator	66	(1)
Alternator service	66	(2)
Checking the rectifier	68	(1)
The regulator	69	(1)
The zener diode	69	(1)
The capacitor	69	(1)
The alternator with external regulator	69	(2)
The 5-terminal alternator	71	(1)
The 3-terminal alternator	71	(1)
Conversion from positive to negative earth	72	(1)
Preparation	72	(1)
Procedure	72	(1)
Dynamo to alternator conversion	72	(2)
Preparation	73	(1)
Procedure	73	(1)
Conversion from a 5-terminal to 3-terminal alternator	74	(1)
Why change?	74	(1)
Procedure	74	(1)
Alternator circuit fault finding	75	(1)
Starting system	76	(10)
General	76	(1)
Starter circuit 1962-1969	76	(1)
Circuit description	76	(1)
Starter circuit 1969-1970	76	(1)
Circuit description	76	(1)
Starter circuit 1971-1975	77	(2)
Circuit description	77	(2)
Starter circuit 1975-1980	79	(1)
Circuit description	79	(1)
Starter solenoid	79	(2)
Solenoid MGB 1962 - 1967	79	(1)
Solenoid MGB 1962 - 1980	80	(1)
Solenoid diagnostics	81	(1)
Starter relay (from 1968 only)	81	(1)
Original relay	81	(1)
Later relay	82	(1)
Alternative relay	82	(1)
Checking the relay	82	(1)
Starter motor	82	(2)
Schematic	82	(1)
Early motor	83	(1)
Later motor	83	(1)
Why starter motors fail	84	(1)
Adding an extra cranking switch	84	(1)
Starter circuit fault finding	85	(1)
Ignition system	86	(27)
Conventional ignition	86	(2)
Electronic ignition	88	(2)
Variable reluctance pick-ups	88	(1)
Constant energy ignition	88	(1)
Magnetic pick-up coils	88	(1)
Hall effect sensors	88	(1)
Optical ignition switching	89	(1)
Capacitive discharge ignition	89	(1)
Electronic ignition spark plug gap	89	(1)
Ignition circuit 1968-1972	90	(1)
Circuit description	90	(1)
Ignition circuit 1968-1972	91	(1)
Circuit description	91	(1)
Ignition circuit 1973-1980	92	(1)
Circuit description	92	(1)
Ignition circuit 1974-1980	93	(1)
Circuit description	93	(1)
Ignition circuit 1974 - 1980	94	(1)
Circuit description (North America)	94	(1)
Ignition components	95	(1)
Ignition relay	95	(1)
Alternative relay	95	(1)
Ignition coil	96	(1)
Why ignition coils fail	96	(1)
Ballast resistor and low resistance coil	96	(2)
Coil selection	97	(1)
Adding a ballast resistor	97	(1)
The ballast resistor	97	(1)
Diode ballast isolation	97	(1)
Schematics for diode fed ballast resistor	97	(1)
Relay ballast isolation	98	(1)
Schematics for relay fed ballast	98	(1)
The distributor	98	(2)
Description	98	(1)
Rotor arm	99	(1)
Capacitor	99	(1)
Distributor variants	100	(1)
Distributor advance mechanisms	100	(7)
Centrifugal advance	100	(1)
Vacuum advance	101	(1)
Electrical vacuum advance	101	(1)
Distributor drive orientation	102	(1)
Distributor clamp	102	(1)
Dwell angle and contact breaker gap	102	(1)
Setting the dwell angle	103	(1)
Ignition timing	104	(1)
Firing order	105	(1)
Drive gear position	105	(1)
Approximate timing	106	(1)
Static timing	106	(1)
Optimising the timing	107	(1)
Anti run-on valve	107	(1)
Spark plugs	107	(3)
Heat range	108	(1)
Standard plugs	108	(1)
Projected nose plugs	108	(1)
Fine tip plugs	108	(1)
Multiple electrode plugs	109	(1)
Exotic metals	109	(1)
Plug gap	109	(1)
Recommended plugs	109	(1)
Spark polarity	110	(1)
Ignition wires	110	(1)
Ignition system fault finding	111	(2)
Lighting	113	(23)
Filament lamps	113	(2)
Voltage effect on brightness	114	(1)
Brightness perception	114	(1)
Voltage effect on lamp life	114	(1)
Light emitting diodes	115	(1)
MGB lighting circuits	116	(2)
Early car lighting circuit	116	(1)
Late car lighting circuit	117	(1)
Lighting switches	118	(1)
Dip switch	118	(1)
Parking lamps	118	(1)
Instrument lamps	118	(1)
Side marker lamps	119	(1)
Halogen bulbs	119	(1)
Fitting halogen headlamps	119	(1)
Beam alignment	119	(1)
Headlamp relays	120	(1)
Installing headlamp relays	120	(1)
Daytime running lamps	121	(2)
Installing DRLs	121	(2)
Linking lighting relays	123	(1)
Turn signals and hazard flashers	123	(2)
Flasher module	123	(2)
Electronic flasher modules	125	(1)
Early car turn signal circuit	125	(1)
Late car turn signal circuit	125	(2)
Using an electronic flasher module	126	(1)
Making turn signals more audible	127	(1)
Brake lamps	128	(2)
Early brake circuit	128	(1)
Later brake circuit	128	(1)
Brake lamp circuit with handbrake warning lamp	129	(1)
Improving lamp earthing	130	(1)
Improving stop and turn signals	131	(1)
Courtesy lamps	132	(1)
Reversing lamps	133	(1)
Light bulb chart	134	(1)
Lighting fault finding	135	(1)
Overdrive & gearbox	136	(6)
Overdrive	136	(1)
Pre-1968 overdrive circuit	137	(1)
Post 1968 overdrive circuit	137	(1)
Post 1977 North American overdrive circuit	138	(1)
Overdrive problems	138	(2)
The gear and reversing switch	139	(1)
The inhibitor switch	140	(2)
Making a start-while-in-gear prevention circuit	140	(1)
Using the inhibitor switch to initiate DRLs	141	(1)
Instrumentation	142	(14)
Instrumentation	142	(1)
Gauges	142	(2)
Moving iron gauge	142	(1)
Thermal gauges	143	(1)
Voltage regulator	144	(1)
Making a semiconductor regulator	144	(1)
Senders	145	(2)
Fuel sender	145	(1)
Temperature sender	146	(1)
Oil pressure sender	146	(1)
Adding an oil pressure warning lamp	147	(1)
Instrumentation circuit	147	(1)
Instrumentation fault finding	148	(1)
Tachometer	149	(4)
Principle of operation	149	(1)
Current driven tachometers	149	(1)
RV1 1419/00 tachometer	150	(1)
RV1 1433/00 tachometer	151	(1)
RVC tachometers	152	(1)
Tachometer calibration	153	(1)
Comparison calibration	153	(1)
Road testing	153	(1)
Calibrating with a battery charger	153	(1)
Calibrating with a signal generator	153	(1)
Tachometer fault finding	154	(1)
Clock	154	(1)
Adding an ammeter	155	(1)
Adding a voltmeter	155	(1)
Wipers & washers	156	(9)
1962 to 1967 wiper circuit	156	(1)
Auto-park operation	156	(1)
The early wiper motor	156	(5)
Auto-park mechanism	158	(1)
Regenerative braking	158	(1)
Adding regenerative braking	159	(1)
1968 and later wiper circuit	159	(1)
The later auto-park mechanism	160	(1)
The later wiper motor	161	(1)
Windscreen washer	162	(1)
Wiper and washer fault finding	163	(2)
Fuel pump	165	(7)
Location	165	(1)
Fuel pump electrical circuit	166	(1)
Fuel pump identification	166	(1)
Fuel pump operation	166	(4)
Capacitor snubbed pump	167	(1)
TVS diode snubbed pumps	167	(1)
Fuel pump service	168	(1)
Fuel pump polarity reversal	169	(1)
Breather pipes	170	(1)
Installing an aftermarket fuel pump	170	(1)
Fuel pump fault finding	171	(1)
Horn	172	(5)
Horn construction	172	(1)
Horn identification	172	(1)
Horn circuit - pre-1975	173	(1)
Horn circuit from 1975	173	(1)
Horn volume	173	(1)
Improving the horn circuit	174	(2)
Using a relay in the early horn circuit	174	(1)
Using a relay in the late horn circuit	175	(1)
Horn fault finding	176	(1)
Cooling & heating fans	177	(3)
Electric cooling fan	177	(1)
Radiator fan circuit	178	(1)
Aftermarket cooling fans	179	(1)
The heater fan	179	(1)
Miscellaneous systems	180	(2)
The sequential seatbelt system	180	(1)
Heated backlight	180	(1)
Fitting a radio	180	(1)
Trailer tow	181	(1)
Appendix 1. Relays	182	(2)
Relay operation	182	(1)
Automotive relays	182	(2)
Appendix 2. Diodes	184	(7)
Rectifier diodes	184	(1)
Over-voltage diodes	185	(1)
Selecting and using diodes	185	(6)
Index	191