In a message dated 10/30/2000 9:21:51 PM Eastern Standard Time, James Fowler
wrote:
> What is the wiring scheme for my 1960 TR3A overdrive? What is the test to
> see if the relay is working? If the relay is not working what is a
suitable
> replacement from my local auto supplier?
James,
The wiring for your OD is as follows (I don't have a TR3A to look at, so the
wiring information is derived from shop manuals - Dave Massey or Randall
Young can correct me if I'm wrong):
>From terminal A3 of the fuse box, a white wire goes to the W1 terminal (coil
hot) of the relay.
>From the W2 terminal (coil ground), a yellow/green wire goes through a
connector to the yellow/green wire of the OD switch.
>From the OD switch, a black wire goes to a connector, which connects to a
yellow wire.
The yellow wire from the connector goes to one of the transmission interlock
switches, and another yellow wire goes from the first switch to the other
switch.
The other side of the transmission switches are grounded by black wires.
A brown wire from terminal C1 (contact) of the relay goes to terminal A of
the generator control box.
>From terminal C2 (contact) of the relay, a yellow/purple wire goes to the OD
solenoid.
When the ignition switch is on, power is applied to the relay coil (W1).
When the OD switch is on, AND the transmission is in the proper gear, the
other side of the relay coil (W2) is grounded through one of the transmission
switches (depending on which gear you are in), and the relay operates.
When the relay operates, terminal C1 is connected to terminal C2 inside the
relay. Power from fuse box terminal A3 is thus connected to the solenoid,
activating the OD.
To test your relay:
1) Verify that you have power on terminal C1 (you should have power here with
the key on or off).
2) With the ignition key on, verify that you have power on terminal W1.
If you don't have power as above, you have some bad wiring in the white
wiring or the brown wiring.
If you have power, turn on the ignition, place the transmission in the proper
gear, operate the OD switch, and check if you have power on relay terminal
C2. If you do, the relay is operating.
If the relay is operating, but the OD solenoid is not, the relay contacts are
not making good contact, there is a break or bad connection in the wiring
from the relay to the solenoid, or the solenoid is bad.
To determine if the solenoid is operating, jumper directly from the battery
to the solenoid.
If you had power on W1 and C1 as above, but the relay didn't operate, either
the relay is bad or the wiring from W2 to the OD switch, the wiring from the
OD switch to the transmission switch, the OD switch, or the transmission
switches are bad.
To determine if it is the relay or the rest of the circuit that is the
problem:
With the key on, use a short piece of wire to connect terminal W2 to ground
(no need to remove the yellow/green wire for this test). If the relay is
good, it will operate.
If the relay is good, you will need to check the switches and/or switch
wiring.
If the relay is bad, you can use a generic (about $5) relay from the local
auto parts store with no problem, but it will not have the correct appearance
- it will be a small cube, about one inch per side. Just buy a relay rated at
30 amps or more, 40 amp is available. To convert from the Triumph relay to
the generic relay, terminal W1 becomes terminal 85, W2 becomes 86, C1 becomes
30, and C2 becomes 87 (when you get the generic relay, these numbers will be
stamped on it)
Note: terminals W1 and W2 are interchangable, as are terminals C1 and C2. It
is possible that someone in the past has reversed the wiring to these
terminals. That is, the white wire may go to W2 and the yellow/green wire to
W1, or the Brown wire may go to C2 and the yellow/purple wire to C1, instead
of as above. The black and the yellow/green wires from the OD switch may be
reversed as well, with no problem.
If all the tests above are satisfactory, but the OD still doesn't work, the
problem is an internal mechanical problem, not an electrical problem.
Dan Masters
Alcoa, Tennessee
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