[TR] TR3A Overdrive Wiring
tr3driver at ca.rr.com
Sun Dec 7 18:00:50 MST 2008
> I had to drill the dash for the switch
That's odd. The hole is supposed to be there, under the vinyl.
> and expect I will have to drill the firewall or tunnel cover for
> the wire pass through. Please advise the correct way the
> wires should go.
The original routing was through a hole in the side of the tunnel, near the
driver's right ankle (for a LHS car). That hole should also be there on a
non-OD car, with a solid rubber plug. However, I didn't like having mine
routed there, so I re-routed it through one of the existing holes in the
firewall (possibly the speedo cable hole, don't recall offhand).
The wiring diagram given in the workshop manual doesn't match what I found
on TS39781LO when I got it. The diagram in "Practical Hints" 4th ed comes
much closer, but the comments still don't quite match. But from looking
closely at several different photographs, I believe my car was correct.
I've attached the diagram from PH4.
43 is the operating switch on the dash.
44 is the relay, mounted to the back of the battery box
45 is fed from the ammeter terminal that also has the brown wire.
46 is the pair of lockout switches on the gearbox top cover (wired in
47 is the operating solenoid on the OD
48 is fed from the "starter push" terminal that also has a white wire.
I also found it advantageous to install a diode across the relay contacts,
to help suppress arcing. Don't recall the exact value I used, but it was
something like 2 amps 50 volts; just an ordinary power diode from the parts
bin. Polarity depends on your battery polarity; since my car had been
converted to negative ground, I put the diode cathode to the wire to the
ammeter and anode to solenoid.
[demime 1.01d removed an attachment of type image/jpeg which had a name of OD wiring.JPG]
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