[Healeys] Overdrive inhibitor switch BN1

Michael Salter michaelsalter at gmail.com
Wed Jul 28 08:14:14 MDT 2021

On the BN1 gearbox the overdrive inhibitor switch is immersed in oil and is
frequently a source of leakage.  The original switch was part # 2H2272
which changed up to 11G3062. The Lucas # for that switch is 31077 and these
are screw terminal switches.
These switches incorporate an "O" ring seal on the plunger to stop oil
leaking through the switch.  After 60 years the "O" rings tend to leak
(appalling quality) and it becomes necessary to  change the switch, as
replacing the "O" ring involves disassembling the switch and usually
doesn't work.
The original Lucas 31077 switches are of course NLA.
Lucas now supplies a Lucar terminal switch as a replacement.
In later applications the "O" ring seal in not required as the switch is no
longer immersed in oil, although on the side shift boxes it is subjected to
oil splash.
I have installed a new Lucas switch on a BN1 gearbox but during a Varsol
leak test it leaks significantly and I'm suspicious that it has no oil
I'm awaiting the delivery of a replacement but was wondering if anyone else
has had success with the currently available switch in a BN1 box.

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