[Fot] A type OD

[Gary Schneider]

A waterproof switch and insulated terminals are a good plan for reliability but won't fix the problem. The switch body needs to be grounded by a separate wire back to the trans or chassis. The lack of a ground means your body becomes the ground path and that is what causes the shock. The moisture provides a leakage path from the switch terminals to your wet hand. The shift lever is not a good ground, as the grease around its base is an insulator.

When the OD switch opens, the solenoid generates a large negative voltage as its magnetic field collapses, same principle as your ignition coil. 12V won't give you a shock but that will. The best solution is a power diode from the solenoid terminal to ground to suppress the kickback voltage entirely. That's standard practice in electronic circuits since the kickback is destructive of electronic controls and switch contacts. The striped cathode side goes to the solenoid terminal, other side to ground. The diode conducts when the negative voltage occurs and harmlessly shunts out the kickback. It could be mounted right on your switch after the ground wire is added.

Example Radio Shack part http://www.radioshack.com/product/index.jsp?productId=2062579

Regards,
Gary Schneider

----- Original Message ----
From: Rob <19to1tr6 at comcast.net>
To: Friends of Triumph <fot at autox.team.net>
Sent: Saturday, March 8, 2008 2:33:31 PM
Subject: [Fot] A type OD

With all the rain in Boston today it reminds me of a problem I need to correct

My OD switch is mounted to a welded tab  on the gear shift lever In a rain
race with soaking wet gloves,suit and shoes I was getting a pretty good shock
each time i activated the OD

The switch  has open poles and is not water proof

Will a water proof switch and insulated mounting correct this Or will i have
other wiring considerations. thanks    rob
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