> Two questions for you guys and gals. First my car has been rewired and
> I am not sure if there is supposed to be a junction box mounted inside
> the firewall behind the master cylinders on a TR3A. My wirintg
> schematic does not indicate one but the schematic is in a TR2 manual.
> Does anyone else have one of these on their TR3A?
Nope, in fact TR2/3 never had a factory fuse in the headlight circuit. Some
PO has grown tired of having the smoke come out, and added a few things to
your car. I've attached the schematic that originally matched TS39781LO,
from Practical Hints 4th Ed. Later cars are fairly similar, except they
have the rheostat for the panel lamps (in the position where my car has the
wiper switch). However, this diagram shows all the fuses the factory ever
> Second question: Does anyone know what the proper level of resistance
> is for a headlight and or tail light circuit should be?
They are both too low for a measurement to mean much. The problem is that
the resistance of the lamp filaments goes down greatly when they are cold
(which is why bulbs almost always fail when you first turn them on, there is
a big surge of current until they warm up).
Scrounge an old headlight bulb and use it to bridge the fuse terminals.
(It's almost always only the low beam filament that fails, so use the high
beam filament. I save old bulbs for just this sort of thing.) Turn the
switch on to just the taillight position. If you have a short, the bulb
bridging the fuse will light (or at least glow brightly) and indicate a
problem. If that's OK, I would suggest next disconnecting the headlights at
the connectors behind the horns, and pulling the switch out to the headlight
position. If that still doesn't show a problem, you know it's between the
connectors and the headlights themselves, so just physically inspect those
lengths of wire.
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