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Re: OD Wiring

To: "Max Heim" <>, "Skye Poier" <>,
Subject: Re: OD Wiring
From: "Paul Hunt" <>
Date: Wed, 22 Mar 2000 19:23:34 -0000
Only the last three years of North American cars had o/d on 4th only, the
earlier cars (both D-type and LH-type) had it on 3rd and 4th.

Late North American cars with the TCSA switch had the o/d lockout switch
wired before the manual switch.

The o/d was always wired off the white (white/brown on ignition relay cars)
i.e. was unfused.  It is a good idea to fuse the circuit but putting it on
the green will take a lot of extra current through that already problematic
circuit.  A better bet would be to use an in-line fuse, but still 17A/35A
for commonality.


----- Original Message -----
From: Max Heim <>
To: Skye Poier <>; MG Nuts <>
Sent: Tuesday, March 21, 2000 11:57 PM
Subject: Re: OD Wiring

> I have (almost) the same conversion in my 66, so I should be qualified to
> advise you...
> I have the plain (not crooked) toggle switch on the dash (the crooked one
> cost 3X as much). It is wired in-line with the lockout switch, or, more
> precisely, I ran a wire from the ignition-on fuse to the dash switch,
> then to the lockout switch, and from there to the solenoid. This gives
> you the following switch conditions:
> Dash switch ON; Trans in 4 = OD ON
> Dash switch ON; trans in R, 1, 2, or 3 = OD OFF
> Dash switch OFF; trans in any gear = OD OFF
> I have the Blue Label OD which only operates in 4th gear -- your Black
> Label OD would work in 3rd or 4th gear. The lockout switch is very
> simple. It has a plunger on the bottom which, when contacted by the
> 3rd-4th gear transmission shift rod, is depressed, enabling current flow
> to the solenoid (ON position). Otherwise, it is OFF.
> I did a rough circuit diagram to get me started -- if you would like to
> see it I could scan it and email it to you. To tell the truth, my circuit
> is a little bit more complex because, in order to fill up a DPO-caused
> hole in the dash next to the OD switch, I wired in a lamp which glows
> when the OD switch is in the ON position (NOT just when the OD is
> operating, but whenever the switch is in the on position -- this is to
> remind me to switch it off). I found this pretty useful; I used a 69 MGB
> ignition lamp to maintain a vintage appearance. [I'm sure this level of
> electrical improvisation will cause me to be cursed as a DPO in due time.]
> One good thing about the 66 -- you can remove the transmission tunnel top
> cover to access the OD lockout switch. I ran my wire from the dash
> through a hole drilled in the tunnel that is hidden behind the speaker
> grille surround.
> Hope this helps.
> Skye Poier had this to say:
> >Ah ha! That explains a lot. See, I have a 4sync+OD conversion in my 66 B
> >and I wasn't sure how the PO wired it up.
> >
> >It appears that the soleniod is always on and they simply wired the
> >lockout switch to a rocker switch on the transmission tunnel which turns
> >the OD on and off.
> >
> >Does this sound like it would work?
> >
> >The downside being of course, don't turn the switch on in R/1/2 !!
> >I haven't done it yet, its not hard to remember to turn it off since I
> >only use it on the highway in 4th.
> >
> >How did the lockout switch originally activate?
> >
> >I would like to replace the tacky lighted rocker switch they mounted on
> >the tunnel with the proper "crooked" switch on the dash.  Would it be OK
> >to hard wire the lockout off and put the switch inline with the solenoid
> >power?  What's the "usual" way of wiring up these conversions?
> >
> >Thanks
> >Skye
> >
> >--
> >1966 MGB - GHN3L     Safety Fast!             __,__\__
> >The MGB Experience   (_o____o_)
> >
> --
> Max Heim
> '66 MGB GHN3L76149
> If you're near Mountain View, CA,
> it's the red one with the silver bootlid.

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