[Healeys] Overdrive Relay

[Bob Spidell]

Yes, there are crap solenoids in the wild (side note: there's also 
rumors that bad actors were buying surplus Lucas boxes and putting 
Chinese crap in them).

Years ago, our own Michael Salter acquired some legit Lucas/quality 
solenoids and offered them for sale. For once, I was smart enough to 
grab one even though I didn't need it at the time, but did a few years 
later. Since the plunger shouldn't wear, and the windings should last a 
long time the most likely failure point is, well, the points (there are 
two in the solenoids: a momentary 'pull up' set and a 'sustain' set--why 
the circuit should have a slow blow fuse). I don't know if they have any 
internal arc protection, but you could probably rig something external, 
though given the cycles the solenoid experiences it shouldn't really be 
an issue. Same issue is in points ignition and our beloved S.U. fuel 
pumps: arcing across the points when a coil field collapses causes 
erosion of the points due to metal transfer. Capacitors ('condensers') 
and diodes can mitigate erosion but, eventually, the points will pit and 
possibly stick.


On 9/23/2024 1:48 AM, Simon Lachlan via Healeys wrote:
>
> The other day my overdrive stopped working. (For the nth time. Toyota 
> 5 speed please Santa).
>
> Anyhow, it failed what I called the “click test” so I was 99%sure that 
> the fault was electric.First off, it’s fused so the wiring was 
> unlikely to be fried and the fuse had not blownThe relay passed its 
> bench test and thethrottle switch was OK.So, I was pretty sure it was 
> the solenoid…..maybe the gearstick switch but didn’t seem likely.
>
> So, I dismantled down to the solenoid. Not too serious in a BT7and 
> much helped by having tunnel cover held down by stainless steelscrews 
> into rivnuts.
>
> Put a test lampin lieu of the solenoid. Lamp lit up when OD was “On” 
> and stick was to the right. So, the problem WAS in the solenoid and 
> final proof was its replacement by a spare which solved the problem.
>
> I took the rubber cover off the top and there was no evidence offrying 
> etc. All looked good.The solenoid was dead as a dodo….putting it 
> across a spare 12v battery didn’t induce a soundor a twitch.
>
> Now, the question(s)……are there dud ones out there? Why/howdid it fail?
>
> Just curious…….
>
> Simon
>
>
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