123GT Gearbox/Overdrive/Reverse lights. Re-fitting help

[MrLeo]

1968 Amazon 123GT
B18 engine (D Type Laycock overdrive)
I snapped the main shaft in the overdrive (too many wheel spins).
Had the overdrive repaired - replaced clutch at the same time.
Now put everything back in place, but I forgot where the wire connect too.

So at the moment:
There's 1 short black wire & 1 long black wire hanging down from the engine bay.
There's 1 wire attached to the o/d solenoid.

Theres the 2 terminals on top of the gearbox.
Theres 1 terminal at the back end of the gearbox(towards back of car)

I have looked at various diagrams but cant work it out.
From the diagram it looks like:
1 short wire goes to the terminal on top of the gearbox.
The wire from the solenoid goes to the other terminal on top of the gearbox.
And then by elimination the long black wire would go to the terminal on the back of the gearbox.


I understand how that could power the solenoid and be able to be cut off via the switch above the gearbox, but where does the power for the reverse lights come from?

WOuld be great to see an idiot proof diagram, as in with an actual illustration of what/where the components are etc. I've searched the entire internet and can not find 1 photo of a wired up gearbox/overdrive

I found this but it doesn't explain things in detail:
http://volvoamazonpictures.se/guides...o%20Amazon.pdf

ie: it says 'remove the reverse light cable'. But doesn't mention if this is a wire or an actual cable? it also doesn't mention or show photos of where the other wires go.

Can't face wriggling about much longer under the car, so would appreciate some help!

Cheers.
LEo

[Ron Kwas]

Leo;

Welcome to this Forum!

Reference Wiring Diagram: http://www.sw-em.com/123GT%20Conside...Wiring_Diagram

Two Black wire you see are:
Reverse input (which will need to be connected to Reverse Switch (13) on Gearbox. It supplies a chassis connection to energize Reversing Lights Relay (16), when in Reverse Gear)
...and OD power (which will need to be connected to 4th gear Lockout Switch (19) on top of Gearbox. It supplies OD Solenoid (25) power from OD Relay (18) by way of this 4th gear Lockout Switch. Another wire will need to be connected between 4th Gear Lockout Switch and Sol.

With two black wires, color codes obviously wont help determining which is which...but length might...otherwise determine which black wire is which by actual function...I suggest assuring all is safe to apply Ignition Power, then applying Ignition Power (Starting not necessary!) with Key and checking for Voltage on the two wires while energizing the OD Control in the drivers position. The OD Power wire will have 12V when OD is activated, and no Voltage when OD is not activated. Find this wire first! (Reverse Relay wire will have 12V continuously, and not affected by OD control.) Once OD wire is determined, other wire is therefore, Reverse Relay input wire...confirm by connecting to chassis...Reverse Relay should clack closed at that time powering Reversing Lights.

Terms "wire" and "cable" can be used interchangeably in this case.

Additional info on OD wiring here: http://www.sw-em.com/OD_Retrofitting...ring_of_the_OD

Good Hunting!

[MrLeo]

Hi Ron
Thanks for the reply, I'm still confused though.
I just can't relate the diagram to the actual gearbox or fully understand what goes where.

I've just created a totally logical illustration showing the 3 available terminals
and the 3 wires that I see.

I've labelled each terminal and each wire.
I don't know which is the lock out switch and which is the reverse switch.

Please could you direct me with an idiot proof instruction based on my diagram.
eg
if wire A is the 12v (always on for reverse) connect to terminal 1.
if wire B is the Overdrive (12v when OD switch is on) connect to terminal 2.
Connect solenoid wire C to terminal 3.



Really appreciate your help!!

[Ron Kwas]

Leo;

Nice drawing!

The following is valid ONLY after you first have confirmed which Black wire is which, by the functional test I gave earlier, because connecting them swapped will be a short circuit and result in blowing Fuse 1, and possible damage to Reverse Contact on Gearbox!

So having stated that, presuming you have determined function of A and B wires as I suggested, I expect wire with Term A (since it's the shorter) to be OD Power, so it should be connected to 4th Gear Lockout Switch on Gearbox Cover (Term 1), and to complete circuit to Sol, other side of 4th Gear Lockout Switch, (Term 2) should get Terminal C.

I also expect longer wire with Term B to be Reverse Relay grounding wire...connect this to Term 3.

Good Hunting!