In a message dated 97-06-17 15:04:49 EDT, todd@nutria.nrlssc.navy.mil (Todd
Mullins) writes:
> I don't know conclusively for your '77, but I've never ever heard of an
> MGB of any year having a fused headlamp circuit from the factory.
Todd and Jason:
I don't know of any car, from any factory, that has a fused headlight
circuit. Believe it or not, this is a safety feature! Given your choice,
which would you prefer - standing by the roadside and watching your car burn
to the ground, or having the headlights go out all of a sudden as you are
driving on a winding back road at 65 mph on a black, moonless night?
Modern automobiles use circuit breakers in some cases for the headlight
circuit. Quite often, as wires fray, they initially make contact with ground
only under certain conditions, such as accelerating, stopping, right turn,
etc. As this happens, the lights will flicker, reminding you to get them
fixed. With a fuse, even a momentary short circuit will blow the fuse and
kill the lights. With a circuit breaker, it takes a little longer, and after
a brief cooling off period, the lights will come back on. A brief short as
described will not kill the lights. Of course, if you get a dead short, you
lose the lights no matter what. There is nothing that can protect against
this. The only line of defense is to maintain the wiring in excellent
condition.
Actually, the stock MG set-up is fully adequate, provided you keep all the
connectors clean, don't install high powered lights, and replace the wiring
if it becomes corroded. Quite often, water will wick up the wire, inside the
insulation, and cause corrosion where it is not readily apparent. As
corrosion spreads, it eats the wire, reducing the cross sectional area,
increasing the resistance. These same concerns also hold true for up-dated
wiring. The actual switch contacts inside the relays are not any larger than
the contacts in the headlight switch. Many times, relays are not used because
of their higher current carrying capacity, but because when they do fail,
they are so much easier to replace than a dash mounted (or especially
steering column mounted) switch.
> Factory Workshop Manual. Don't fly without it.
Absolutly! Before you even begin to do electrical repairs, study the manual
carefully. Without a wiring diagram, you will be hopelessly lost.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
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