Dan,
I am once again amazed (not surprised) at the detail in your responses
to questions like mine. I got into it a little more deeply this
morning, before reading your answer, and found out something
interesting. First, as you point out, I had the ballast resistor
wire mixed up with the seat belt wire. But I THINK the brown wire
which connects to the coil along with the white/yellow one is actually
the resistor wire. It is cloth wrapped and dirty but it does sort of
resemble a shoelace and it has a pinkish sheen to it when wiped
clean. It is no fatter than most of the wires, and I was expecting a
fat one for the ballast resistor. So if I'm right (now) the ballast
resistor wire and the white/yellow come together right at the coil.
That would be okay, right? The really interesting thing is that
the PO put in a horn relay instead of a start relay. In other words
there are two horn relays. From looking at parts catalogs, it appears
that the start relay was indeed the same as the horn relay up through
1973. It costs about $40 dollars less than the correct start
relay for my 1974! Anyway it has no C4 connector for the white/yellow
wire.
Cheapskate that I am, I am wondering if it would be possible to make
do with the horn relay as my start relay. My first thought was that
it might be okay if the white/red wire to the solenoid and the white/
yellow one to the coil are joined so that both carry voltage (connected
to brown) when the relay is energized. Would it be bad for those two
to be joined all the time when not carrying voltage?
And one question about your instructions. The white/red wire from
the ignition switch that should replace white/orange at the W1
connection; that is not the same as the white/red normally connected
to C1 is it? Because if it IS, then I think I can use the horn relay
and still keep everything separated until the relay is activated.
Just this minute I received your schematic for the '74 TR6. Thank you
a million times over!!
Tim Gaines
1980 Spitfire
1974 TR6
>In a message dated 5/13/99 5:42:47 PM Eastern Daylight Time,
>mtgaines@cs1.presby.edu writes:
>
>>
>> To Dan Masters or anyone else who can help me with a wiring problem:
>>
>> I have a question about wiring on a '74 TR6 for you. My Haynes manual,
>> which came with the car when I bought it in October, does not have
>> a wiring diagram which matches my car. The previous owner has
>> made a number of changes associated with the ignition system. First,
>> he bypassed the original ignition switch which was torn up but still
>> mounted on the steering column. I have removed the original one and
>> the replacement the DPO put on and have installed a new correct one.
>> But the DPO also bypassed the fat white/red wire from the ignition
>> switch with a shunt to the relay? under the bonnet on the left. From
>> experience with my Spit I suspect that the fat wire is the coil ballast
>> resistor. He also installed a HUGE coil which has its own ballast
>> resister alongside. Two wires connect to the ballast resistor from the
>> harness; a brown one and a white/yellow one. I suspect that normally
>> the white/yellow one would carry the reduced voltage from the resistor
>> wire during running and that the brown one would carry full voltage only
>> at startup. I have ordered a new coil and plan to use it with the
>> original ballast resistor wire in place. My problem is that the white/
>> yellow wire has been cut right next the two relays under the bonnet
>> and I can't tell where it should connect. I think I could figure it
>> out if pressed to do so, but I would feel much better if someone could
>> tell me for sure. I checked a buddy's '76 TR6 but the wires to his
>> relays are a little different and there is no white/yellow one. Thanks
>> for any help you can provide. If I'm off base here I'd sure like to
>> find out before I do something stupid!
>
>Tim,
>
>Let me see if I can help. From your description, it sounds like the PO
>bypassed the seatbelt interlock system.
>
>The '75 and '76 TR6s used a wiring scheme that is slightly different than
>your '74, so you won't get much help there.
>
>
>As equipped, your car was wired as follows:
>
>The white/yellow wire carried EITHER the full 12 volts OR the reduced ballast
>voltage, depending on the state of the starter relay. One end of this wire
>connected to the + terminal of the coil, and the other end connected to the
>C4 terminal of the starter relay.
>
>The ballast resister was a piece of pink and white wire, looking like a
>"shoelace" and was bound up in the harness. One end of the ballast wire was
>spliced to the white/yellow wire, close to the coil. The other end was
>spliced, inside the harness, to the white wires coming from the ignition
>switch. The white wires are hot when the key is in the "RUN" or "START"
>position.
>
>When the starter relay was energized, it supplied the full 12 volts to the
>white/yellow wire, bypassing the ballast resister. When the key was in the
>run position, and the starter relay was de-energized, the 12 volts was NOT
>supplied to the white/yellow wire, and the coil got its power from the white
>wires through the ballast resister, supplying the lower coil voltage.
>
>Your starter relay was wired:
>
>C1 - white/red
>C2 - 2 brown wires
>C4 - white/yellow wire
>W1 - white/orange wire
>W2 - black wire (ground)
>
>When the relay is de-energized, C1, C2, and C4 are isolated from each other.
>When the relay is energized, these three termionals are all connected
>together inside the relay. The brown wires are hot ALL THE TIME, so when the
>relay is energized, power is supplied from the brown wires to the to both the
>white/yellow and the white/red wires. The white yellow wire is the ballast
>bypass to the coil, and the white/red supplies the power to operate the
>starter solenoid.
>
>The white/orange wire came from the seat belt interlock module, and had power
>on it when the ignition key was in the "start" position AND all the seat belt
>interlock conditions were satisfied.
>
>The white/red wire from the ignition key is hot when the key is in the
>"start" position only, and went to the seat belt module. This white/red wire
>connected to the white/orange wire inside the seat belt module when all the
>seat belt interlock conditions were satisfied.
>
>So, now what? First, check to see that the relay is wired as I described
>above. If not, let me know, and I'll try to figure out what to do. If it is,
>connect the white/red wire from the ignition switch to terminal W1 of the
>relay. Connect the end of the white/yellow wire that's near the relay to
>terminal C4 of the relay. If you have the white/orange wire still connected
>to the relay, disconnect it and tie it back out of the way. Probably nothing
>would happen if you left it where it's at, but it's better to be safe and
>disconnect it.
>
>Connect the end of the white/yellow wire that now goes to the ballast
>resister to the + lead of the coil, and remove com-letely the brown wire.
>
>All of the above is assuming the ballast resistor is still intact in the
>harness. If it is not, the car will start, but it will stop as soon as you
>release the key from the start position (unless the PO has done something
>strange with it).
>
>In a seperate post, I'm sending you a copy of the '74 schematic.
>
>Hope this helps!
>
>Dan Masters,
>Alcoa, TN
>
>'71 TR6---------3000mile/year driver, fully restored
>'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
> http://members.aol.com/danmas/
>'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
>'68 MGBGT---organ donor for the '74
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