Michael,
Here's how the thing is supposed to be wired:
(there may be some bullet connectors in the paths that I am not calling
out)
Relay:
C1 - Connected to switched power so the circuit is only on when the
ignition is turned on.
C2 - Connected to the input of the solenoid.
W1 - Connected to a fused power source (typically the hot side of the
coil)
W2 - Connected to one of the switch terminals
Switch:
One terminal connected to Relay connection W2
The other terminal is connected to the input of the two gear switches
(what you call isolators).
Solenoid:
Input connected to Relay terminal C2
Other side connected to Ground
Gear selector switches:
These are connected in parallel (inputs wired together and outputs wired
together)
Input is connected to the Switch
Output is connected to ground.
Theory:
When the ignition is turned on the relay is energized if the following
conditions exist:
The switch is ON and either of the gear selector switches are closed.
The circuit is completed because the current flows from the power source
through the relay windings through the closed switch through one of the
gear selector switches to ground. The energized windings of the relay
cause the contacts to close and cause the circuit that energizes the
solenoid to be completed.
I hope this helps,
Joe
Michael Ferguson wrote:
>
> PLEASE HELP! I'm about as electrically challenged as is humanly possible and
> I'm getting ready to install an A-type OD gearbox in my TR3A. The box came
> out of a TR4 and the wiring to the relay was lamp cord (and not connected to
> anything at the other end anyway) so I can't tell where the wires are
> supposed to connect.
>
> The isolator switches are wired with what appears to be a legit harness, but
> it's not connected to anything either. The front isolator has a yellow and a
> black wire. These connect to the rear isolator. The yellow continues on to
> the other end of the harness and quits there. The black goes to ground (or
> earth) on the case.
>
> The tail end of the isolator harness (about 18" long) has the yellow wire
> and also a yellow/purple wire. Up near the switches themselves is the other
> end of that yellow/purple, also not connected.
>
> Bought a new switch and it has two gray wires.
>
> The relay has four terminals; C1, C2, W1 and W2.
>
> The OD solenoid has a single gray/purple wire.
>
> Can any of you tell me what connects to what? Please be as specific as you
> can as I'm not kidding about being challenged! I hope this doesn't involve
> using a meter of any sort. I don't own one and wouldn't know what to do with
> it if I did!
>
> Oh, and one last question...where is the relay supposed to be mounted on a
> '3A?
>
> As always, thanks very much for your sage advice.
>
> Michael Ferguson
> 1959 TR3A TS53990L (soon to be "O")
> Connecticut
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