[Healeys] Overdrive wiring question

Bob Spidell bspidell at comcast.net
Mon Sep 4 22:38:50 MDT 2017

I used the ol' 2x4 braced against the pedal to get the nominal setting 
(but I thought it required too much pedal and the OD didn't always 
deactivate when I assumed it would).  I think it's a bit of personal 
preference; I adjusted mine so just a quarter of a clutch pedal and a 
quick blip--less than a downshift--would disengage the OD.  Done just 
right, it's smoother than my best downshift, so I gotta believe it's OK 
on the internals.  This OD has almost 200K miles and the only problems 
(2) I've had with it were electrical.

Anyway, glad it's in the manual; I was beginning to wonder ...

On 9/4/2017 3:15 PM, BJ8Healeys wrote:
> The manual says:
> "Connect a low-consumption test lamp (a 12 volt 2.2 watt fascia panel 
> light bulb is suitable) [I made a test lamp out of a single filament 
> turn signal bulb and a spare bulb holder I had lying around] between 
> the top terminal "A" (Fig. G.13)[of the throttle switch] and a 
> convenient earthing point.
>   The bulb should light when the overdrive and the ignition are both 
> switched on, and the gear lever is set in the third or top gear position.
>   When the overdrive is switched off, the bulb should remain alight 
> with the throttle still closed.
>   Progressively open the throttle by means of the accelerator pedal 
> until the light goes out. Check the position of the throttle opening 
> when this occurs:  it should be one-fifth open.  This position of the 
> throttle has been reached when a 3/16 in. (5 mm.) diameter rod can be 
> just passed between the throttle stop screw and the stop lever on the 
> HD type of carburetter, or when a feeler gauge of 0.048 in. (1.22 mm.) 
> thickness can be inserted between the throttle stop screw and the stop 
> on the H4 type of carburetter used on earlier engines."
> The manual procedure would account for any system slack, but it also 
> requires two people:  one to operate the pedal and another to monitor 
> the light and check the position of the throttle plates when it goes 
> out. It would also require access to the throttle plates, and an 
> estimate of what is "one fifth open".  If that is related to the 3/16" 
> rod, then why not just use the rod and adjust until the light goes out?
> I have an "overdrive warning" light just above the dash switch that I 
> installed back in the '80s when I didn't mind drilling a new hole in 
> the dash.  When the switch is adjusted properly, the light stays on 
> when the dash switch is turned off and then goes off with what seems 
> to me a reasonable movement of the pedal.  I would say it isn't 
> necessary to account for slack in the system when using the 3/16" rod.
> Steve Byers
> HBJ8L/36666
> BJ8 Registry
> AHCA Delegate at Large
> Havelock, NC
> *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of 
> *Bob Spidell
> *Sent:* Monday, September 04, 2017 1:14 PM
> *To:* healeys at autox.team.net
> *Subject:* Re: [Healeys] Overdrive wiring question
> I'm working from memory--will check the manual later--but the way I 
> interpreted the instructions were to adjust the switch with the 
> throttles a spec distance--prob. the 3/16" as Steve mentions--opened.  
> For some reason, I thought this should be achieved by pressing on the 
> accelerator pedal to achieve this setting which, of course, would pull 
> up any slack in the Rube Goldberg throttle mechanism.  So, I set it 
> this way but felt that it required too much pedal when disengaging the 
> OD.  I just fiddled with the adjustment to where the OD disengaged 
> with what I felt was appropriate pedal.  Maybe the 3/16" should be 
> measured without allowing for linkage slack, maybe not; does anyone 
> know for sure?
> Bob

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