[TR] TR4 ignition switch

Randall TR3driver at ca.rr.com
Fri Mar 20 21:08:14 MDT 2020

The number on the front (31873D) appears to be correct for TR4 (listed in my
1963 Lucas catalog).  The illustration in the catalog doesn't clearly show
the back of the switch, but from what I can see, it's pretty close.  The
wiring diagram shows 7 wires going to the switch (when overdrive fitted), so
I'd expect roughly that many terminals.

I've not found a good way to clean those old Lucar terminals; but you can
usually coax them back into service by spraying with Deoxit (or similar),
pinching the ears tighter with needle nose pliers, then sliding on and off
the terminal a couple of times to break up any oxide on the contact areas. 

The other solution is to replace them.  Here's a little slide show on how to
replace them

Lots of other things can cause that problem, so I would want to do some
checking before replacing the switch.  If you can duplicate the problem with
the switch out, use a test light between the terminals with white wires and
the brown/blue wires.  If the light lights with the switch in the 'On'
position, the switch is bad.  Otherwise, the problem is somewhere else.

-- Randall 
56 TR3 TS13571L once and future daily driver
71 Stag LE1473 - awaiting engine rebuild
71-2-3 Stag - awaiting gearbox rebuild 

> Anyone recognize this switch?

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