In a message dated 98-05-19 22:48:47 EDT, mmbent@email.msn.com writes:
> Seriously though I am at
> the pre production, feasibility stage of this project and need some input
> from the collective wisdom to help me figure out what really should be
fused
> and what gauge of wire I really need. (Dan Masters are you listening??)
Craig,
Yeah, I'm listening! I don't know if you are crazy or not, but if wanting to
build a harness from scratch with improvements makes you crazy, then there's
two of us. If I weren't going to sell my stock TR6 when the V8 conversion is
done, it would have a new harness, made to suit my ideas of what a wiring
scheme should be. I did make a new harness for the V8 conversion, using 9
fuses, 4 fusible links, 5 relays, and a custom fuse/relay panel mounted inside
the cockpit. I really had to struggle to get by with 9 fuses!
Go for it!
A few observations/comments:
1) size the wire to the load. If a device draws 5 amps, the wire feeding it
must be rated for 5 amps.
2) size the fuse to the wire. If the wire feeding a device is rated at 5
amps, the fuse MUST NOT be rated for more than 5 amps. With very few
exceptions, the ONLY purpose of a fuse is to protect the WIRE, not the device!
3) if a fuse feeds more than one wire, the fuse MUST BE sized no greater than
the SMALLEST wire being fed by the fuse. For example, you run a 10 amp wire
to a connector and run two wires rated at 5 amps from the connector to each of
a pair of running lights. The fuse must be no larger than 5 amps.
4) to state # 3 in another way, the smallest wire in any circuit must be able
to carry a current AT LEAST as high as the fuse protecting the wire. If you
put six 5 amp loads on one 30 amp fuse, EVERY wire in the circuit (other than
the ground wires) must be rated to carry 30 amps. Ground wires need to be
sized only to carry the current of the device being grounded -- if you short a
ground wire to ground, so what?
5) DO NOT use fuses in the headlight circuit. If you want to protect the
lighting circuit, use a circuit breaker instead. If you insist on using
fuses, use one fuse for highs and one fuse for lows per side (4 fuses), and
check your headlights on a regular basis and immediately replace any that is
burned out.
6) re-read numbers 3, 4, and 5.
7) DO fuse all other circuits, including all other lighting circuits. Use
fusible links where it is not practical to use fuses.
8) there are two advantages to using relays to switch high current loads: a)
it is hard to find a good switch to handle high current loads and still look
half way decent in an automobile, and b) if you place all the relays under the
hood, you can significantly reduce the size of the wires that have to run
inside the cockpit, making it much easier to route the harness. Or, do as I
did and place the fuse panel under the dash, close to the firewall, so that
all the heavy wires exit the cockpit immediately at the panel so that only one
major bend is required in the harness.
9) review the two articles on the VTR web site dealing with making wiring
harnesses and swapping a GM alternator for the Lucas unit in a TR6.
10) I'm sure I'll think of more later. If you have any questions, call on me.
If you would like to send me copies of the wiring diagrams you come up with, I
would be happy to review them and make comments/suggestions. You might want
to go to the web site below and check out the wiring panel on my car.
Dan Masters,
1051 Vera Drive
Alcoa, TN 37701
'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 - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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