[Healeys] Odd Overdrive Electrics

[Roger Grace]

I would be suspicious of your OD switch staying closed. Exercise it  and
give it a squirt of contact cleaner.
Alternatively the OD relay could be sticking and not releasing freely. Same
story connect 12v directly and cycle and listen to it.
Just for interest see my simplified OD cct sketch
rg

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On Sun, Aug 24, 2025 at 6:00 AM Bob Haskell via Healeys <
healeys at autox.team.net> wrote:

> Patrick,
>
> Thinking out loud here.  The hydraulic pump in the overdrive is always
> supplying pressure.  When you turn the OD switch to Overdrive the solenoid
> moves a linkage in the overdrive to open the hydraulic valve.  When you
> flip the OD switch to Normal, the throttle switch keeps the solenoid
> energized so the hydraulic valve is still open.  When you press on the
> accelerator pedal, the solenoid de-energizes, the hydraulic valve closes
> and the OD goes to direct.
>
> It seems like the hydraulic valve is moving since the OD goes to direct
> when you press on the throttle.  So, the solenoid would have to be
> energized to move the valve again.
>
> When you first start out, with the OD in Normal, it doesn't attempt to go
> into Overdrive, right?
>
> When I am coming to a stop with the car in Overdrive, I flip the switch to
> Normal, put the gearbox in neutral, and blip the throttle. I then move the
> gear shift lever left and right.  If I hear the solenoid engaging when I'm
> next to 3rd/4th and disengaging next to 1st/2nd, I know the OD solenoid
> circuit is still energized and blip the throttle again.
>
> If you put the gearbox in neutral, do you hear the solenoid when you move
> the gear shift lever left/right?
>
> Cheers,
>
> Bob Haskell
> Austin-Healey 3000 roadster registrar
>
> On 8/24/25 05:27, Patrick and Caroline Quinn wrote:
>
> G’day
>
>
>
> Thank you to those who responded concerning how best to adjust the
> overdrive throttle switch.
>
>
>
> Well I did what was suggested and have the overdrive cutting out when the
> accelerator is pressed about a fifth of the throttle opening.
>
>
>
> I wish that was as simple as that, because what’s happening next is
> confusing.
>
>
>
> What’s happening is that I could be driving along in top overdrive. Flick
> the switch to “Normal” and it behaves as it should, staying in overdrive.
> Press down on the accelerator and it changes down to direct top. So far so
> good.
>
> Ease up on the accelerator and does it stay in direct top? No, it goes
> back into overdrive even though the dash switch is still on “Normal”.
>
>
>
> Any ideas?
>
>
>
> Hoo Roo
>
>
>
> Patrick Quinn
>
> Blue Mountains, Australia
>
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