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Austin-Healey BN1 Overdrive Challenges

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Gloria

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Good Afternoon All,
I've been trying to figure out an issue with my overdrive. It was working and then quit. I went through the test procedures and determined the Throttle Switch was bad. For good measure, as all of the electrical components in this circuit were over 20 years old (last time I had to replace any) I ordered in new 1. Throttle Switch 2. Both relays R1 and R2 3. The Dash Switch 4. Top gear switch 5. Solenoid (the centrifugal switch is by passed). Replaced all of the components, adjusted accordingly, changed the oil and cleaned the magnets and control valve. Out for a test ride. All works great. Went for a 200 mile club outing, overdrive performed great...until after exiting the highway and stopping for lunch. Upon continuing our trip the overdrive would not engage.

Problem: overdrive won't engage automatically
Double checked adjustments, checked and changed oil. Still will not work automatically. With cover off, can move linkage on RH side of overdrive and engage manually. Additionally, with switch on can lift up on solenoid plunger and overdrive will engage and remain engaged until slowing down as normal. Should this indicate the pull up circuit in the new solenoid has failed?

Thank you for any help,
Rob
 
I'm sure that there are a lot more knowledgeable folks that can contribute, but I just watched Matthew Randell's newest YouTube video, "Austin Healey 100/6 restoration Pt. 55", where he discusses an issue with his solenoid that might be relevant to your problem.

If you haven't watched his videos, IMHO, they're a real treat. I think Matthew is my new hero!

GL, Jim
 
It is usually the solenoid, I've just had a Lucas one failed after a few hundred miles, so I bought one from SC Parts who have theirs made in Germany.

There are two coils in the solenoid, a high current one to pull it in and a low current one to hold it in. There are change over contacts are under the plastic cover and they might be repairable, but I'd get one from SC.

https://www.scparts.co.uk/sc_en/bri...1-to-bj8-1952-1968/gearbox-and-overdrive.html
 
Hi Rob and thanks Jim
It turns out the solenoid was fitting on a slight angle causing the plunger to bind a bit and not return properly sometimes. I fixed it by fitting a thin shim under one side of the mount. Maybe this is your issue Rob.
Matthew
 
With your ignition on and OD switch on (engine not running), does the solenoid click in and out when you move the shift lever from full side to side in the neutral corridor? If it does there has to be something mechanical wrong between the solenoid and the activation lever on the RH side. If it does not you have an electrical problem. You can always just bypass everything with a 12 V jumper lead to the hot side of the solenoid to see if it works at all. Are you saying that if you run the engine with the rear wheels jacked and put it in 3rd or 4th you can manually engage the OD as witnessed by a drop in tach RPM? If you can do that then the solenoid is probably the problem and it could be rigging or electrical.
 
Update
Good Afternoon Gentlemen and Ladies,
After a little double checking of all the connections I found the problem. The last connection in the overdrive wiring loom to the solenoid was faulty. I had to change the connection previously from the round type connector to the flat spade type to accommodate the new solenoid. I'd placed heat shrink over the wires for protection however; when crimping the new connector I hadn't got as good a crimp as I'd thought. Upon double checking, when I tugged on the wires the one connection separated from the wire. So now it's sorted. The overdrive works as advertised. Now to reinstall the interior and enjoy the fall cruising.

Cheers,
Rob
 
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