[TR] TR3A OD Wiring Harness Install

Randall tr3driver at ca.rr.com
Mon Jul 23 06:41:37 MDT 2018

> I am
> going by the wiring diagram in the TR3 owners handbook manual 
> and want to
> confirm the setup listed there.

IIRC there are some small differences between various editions, but all of
them should work.

> Wires currently installed to relay by PO which look incorrect based on
> diagram:
> C1 - Nothing
> C2 - one wire to solenoid on tranny OD
> C4 - 1 wire from OD switch on dash
> W1 - one wire to body ground
> W2 - 1 wire from OD switch on dash and 1 wire from starter 
> push button (hot
> when ignition on)

Yup, that's mostly wrong.  One way that does work (from PH 6th ed) is:

C1 - Constant power from before the ammeter.  Connect either to supply side
of ammeter, or fuse block terminal with the brown wire.  I recommend adding
an in-line fuse holder to this wire, with an AGC 5 fuse.
C2 - to solenoid
C4 - open (not present on original relay)
W1 - from OD switch on dash
W2 - to isolator switches on gearbox top cover.  Both switches are wired in
parallel, meaning this wire goes to both switches; and the other side of
each switch is grounded.

In addition, you'll need a wire from the ignition switch load terminal
(white wire) to the OD control switch on the dash.

I also found that it improved relay life to add a solid-state diode (eg
1N4001) from C2 to ground.  Orientation will depend on battery polarity.

-- Randall  

More information about the Triumphs mailing list