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Dave (and others who may be concerned),<br><br>
Okay, surprised no one has jumped on this yet, so I'll give it a
shot. The referenced color wiring diagram is not my doing, but is
posted with permission of the developer. My own wiring diagrams are
broken down into smaller and simpler sub-sets. This will be a
collated summary of details found on multiple pages of wiring diagrams,
harness routing and snap connector info. Some day I should post
another web page with a full car layout showing general routing of the
harness and locations of all of the snap connectors (harness
junctions). The factory was not concerned with this, because they
gave you a complete car with the harness already installed. Very
few people realize how many of these tube connectors there are in one
car. Parts suppliers often do not include enough of them in
connector kits. The complete list of snap connectors for MGA is
here:
<a href="http://mgaguru.com/mgtech/electric/circ_snap.htm" eudora="autourl">
http://MGAguru.com/mgtech/electric/circ_snap.htm<br><br>
</a>The main harness runs through a rubber grommet at center of the
bulkhead (behind the heater box). There are minor branches for the
wiper motor (3 wires), heater blower, (<b>2 snap connectors
there</b>) and control box (multiple wires including two Black ground
wires), and for the turn signal relay (8 wires) for the 1500 model
only. Other branches go to the fuse block, flasher unit, and Black
wire break-outs for chassis ground on the front side of the bulkhead near
the fuse block.<br><br>
Otherwise the main harness continues to the right side inner wing where
there is a bundle of <b>snap connectors located near the starter
switch</b>. This is the junction (interconnection point) where the
side harness (sometimes called chassis harness) connects to the main
harness. There will be many snap connector circuits here:<br><br>
Red (parking lights) 3-way (twin tube)<br>
White (fuel pump)<br>
Green (input to stop lamp switch)<br>
Green/Purple (output from stop lamp switch, 1500 only)<br>
Green/Black (fuel sender unit)<br>
(White/Purple (left rear turn signal 1500 only)<br>
(White/Brown (right rear turn signal 1500 only)<br>
Green/Red (left turn signals 1600 only, 3-way twin tube)<br>
Green/White (right turn signals 1600 only, 3-way twin
tube)<br><br>
From there the main harness continues forward along the right inner
fender, breaking out wires for the dynamo and ignition coil, to a point
in the <b>RF corner of the main body nose</b>, just above the air
pan. Here you should have 2 large ring connectors with 2 Black
wires each (grounding wires) attached to the inboard end of an extra
length wing bolt with a hex nut (2nd bolt up above the air pan).
That has nothing to do with snap connectors, but is a general point that
many people get wrong.<br><br>
In the same location, just inside the right front corner of the body
nose, there should be a group of snap connectors for the right hand front
lights:<br>
Blue/White headlight high beams (3-way twin tube)<br>
Blue/Red headlight low beams (3-way twin tube)<br>
Red parking lights (3-way twin tube)<br>
Green/White (RF turn signal).<br>
Black ground (4-way twin tube) for RF headlight, RF side light, local
grounding wire, and one more black wire continuing to opposite side of
the car.<br><br>
From there the main harness continues across to left side, following
under the bonnet latch brace with a couple of P-clips, to a point just
inside the <b>LF corner of the main body nose</b> above the air pan
(similar to the right side arrangement) for the LH front lights You
have a few less snap connectors here: <br><br>
Blue/White headlight high beams<br>
Blue/Red headlight low beams<br>
Red parking lights<br>
Green/Red (LF turn signal).<br>
Black ground (3 or 4-way twin tube) for LF headlight, LF side light
(maybe 2 lack for 1600 type side lights), and the black wire coming from
opposite side of the car.<br><br>
Additionally, at the RF corner there are 2 wires for the horn(s) and one
wire for the fog lamp(s) wrapped together. These wires drop down
through rubber grommet in the air pan and cross below the air pan.
When you have the <b>optional second hor</b>n there will be a 3-way (twin
tube) snap connector for horn power, and another 3-way (twin tube) snap
connector for horn switch return. If you have one fog lamp
installed, there should be a snap connector to connect that lamp.
With no fog lamp there should be one snap connector to cover the wire end
to prevent shorting the power wire to ground. With two fog lamps
you may have one 3-way twin tube connector for fog lamp power. The
fog lamps commonly have a local grounding point on the bumper at the lamp
mounting bracket for the Black ground wire from the lamp. Some
people prefer to us an additional 3-way twin tube snap connector to run
these Black ground wires back to body ground at the RF corner of main
body shell.<br><br>
If you have <b>more than one fog lamp or driving ligh</b>t, it is also
recommended to run a separate power wire and use a relay to remove this
larger electrical load from the fog lamp switch, or more importantly to
remove the larger power load from the lighting switch (parking lamp red
wire circuit). Also notice that the original fog lamp harness wire
is only 18-gauge wire, not intended to carry enough power for two lamps
(especially not two high power driving lights). You will see that
headlight wires and horn wires are heavier wires. This stuff about
multiple fog or driving lights is variable at the owner's discretion, as
these parts were dealer (or owner) installed options with variable style
installations. Just keep in mind that multiple lamps (and multiple
horns) will involve more 3-way 2-barrel snap connectors for
splitters.<br><br>
As to the exact location of snap connectors at the front corners of main
body, original factory issue placed these connectors above the air pan
for environmental protection, while all of the wires for front wing lamps
ran down through a rubber grommet in the air pan. This is nice and
neat, but significantly inconvenient for service, as these locations are
difficult to reach, perhaps requiring removal of the grille and 4-inch
air hoses to gain access to the snap connectors. For my car I have
relocated all of these snap connectors to be below the air pan for easier
access from below. This leaves the connectors more exposed to road
splash, but once you learn how to deal with this issue it may become a
non-issue.<br><br>
Warning, no new snap connectors in this next paragraph. Getting
back to the bundle of snap connectors near the starter switch, this is
the front end of the side harness running below the frame on right side
of the chassis. Just aft of the RH seat there is a White wire
break-out for the fuel pump (no snap connector), while the fuel pump has
a single Black wire to ground locally on a floor board bolt with a hex
nut (no snap connector). Farther back, aft of the wheel arch of the
frame, there is a Green/Black wire break-out for the fuel level sender
unit (no snap connector). The sender unit grounds to the fuel tank,
which was originally grounded through the steel fuel pipe to the fuel
pump, which in turn had the Black ground wire to the frame. If the
steel fuel pipes have been cut, and the fuel pump is connected with
rubber hoses, then you should add a black grounding wire from one of the
sender screws to a tab on the frame nearby.<br><br>
Continuing aft of the fuel fuel sender along the right side frame, there
will be another bundle of <b>snap connectors aft of the rear wheel</b>,
just behind the rear splash panel. This is the junction point
between side harness and rear harness. Circuit wires here will
be:<br>
Red parking lamps, 4-way twin tube connector, Power in, RH tail light,
Tag lamp, LH tail light.<br>
Black grounding, 4-way twin tube for 1500 cars, or 6-way triple tube for
1600 type.<br>
White/Brown, RR brake and turn signal, 1500 only<br>
White/Purple, LR brake and turn signal, 1500 only<br>
Green/Purple, brake lights, 1600 only<br>
Green/White, RR turn signal, 1600 only<br>
Green/Red, LR turn signal, 1600 only<br><br>
For ground returns of the rear harness, all of the Black wires come
together at RR corner bundle of snap connectors (4 or 6 black
wires). One of these wires will be for the local grounding point on
the frame. My diagrams show this grounding point to be on a frame
tab hear the fuel sender unit, which means there is a Black wire in the
side harness. This is original factory design (at least for the
1500 cars). Some recent issue replacement wiring harnesses make
this rear grounding point on one of the large bolts securing the forged
bumper mounting bracket to the frame. This set-up has no black wire
in the side harness (but still the same number of snap
connectors).<br><br>
There are three additional snap connectors under the dash. Two of these
connect the switch for the heater blower. One connects the
Brown/Black wire between main harness and dash harness for the horn
switch wire. This last one is the only interconnection between main
harness and dash harness.<br><br>
Hope this helps. Anyone is welcome to wave and whistle if I missed
anything.<br><br>
Barney Gaylord<br>
1958 MGA with an attitude<br>
<a href="http://mgaguru.com/" eudora="autourl">http://MGAguru.com<br><br>
<br>
</a>At 09:59 AM 2/6/2020, dave via Mgs wrote:<br>
<blockquote type=cite class=cite cite="">....<br>
I really wasn’t clear the first time. I’m trying to figure out
where exactly on the car these snap connectors are located, or if I
should just put them where it makes sense to me. Maybe take
into account where they go through holes in the sheet metal.<br>
<br>
In Barney’s wiring diagram
<a href="http://mgaguru.com/mgtech/electric/circ_wiring.htm">
http://mgaguru.com/mgtech/electric/circ_wiring.htm</a><br>
<br>
There are several places where he has a nice line of snap
connectors. Two up front (I assume) close to the headlights, one
off to the side, maybe in the engine compartment??? And a fourth set
maybe in the tail????<br>
<br>
Can anyone share where these connectors are on the car? Are they in
fact together? <br>
<br>
My car was wired by a guy that loved red, blue, and black wires. I
just tore it out because it was so wrong so I’m planning on building the
wiring harness myself. It won’t be the first car I’ve wired from
scratch without a harness. Any help on where to put these snap
connectors would be appreciated.<br>
....</blockquote></body>
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