Gearbox switches?

[Mark Serj]

Hi all,

On the upper LHS of my manual box (with O/D), there is a switch, of the same format as one on the upper face adjacent to it. Am I correct in thinking the LHS switch is the reversing light, and the one on top some kind of O/D related inhibitor switch please?

Minor confession here in that I have lost the record I made of the wiring for these two when I took the motor out.

I can't find any reference to anything other than the reversing light switch in the Haynes wiring diagram.

Thanks in advance for help

Regards


Mark

[Lingen]

Mark.
That is correct. Reverse light switch on the side, and the one on the top is to ensure that the overdrive only works on third and top gears.
Mike.

[Mark Serj]

Cheers Mike - strange that I can't see any reference to this switch in the Haynes wiring diagram. Either that or I'm being thick!

Thanks again

Mark

[DJT]

Taken from ROM, which is the same diagram as Haynes uses. Switch is item 86:




Screen Shot 2017-02-02 at 15.46.34.jpg

[Mark Serj]

Aah, sussed it now - thank you

[DJT]

You're welcome

[Tim Proctor]

On the subject of the reverse light switch, our switch does not work, and the problem seems to be the plate that is supposed to push the switch in. It jiggles a little when reverse is selected, but it doesn't actually move, and I've a feeling it should slide along and depress the light switch. Reverse selects OK, although the gear lever has taken to revolving around.

[mole42]

IIRC the reverse lamp switch is operated by a detent in the reverse gear selector rod. There are three gear selector rods in the remote gearchange assembly on top of the gearbox, 1st/2nd, 3rd/4th and reverse, they have sprung interlocks to stop more than one gear being selected at any one time. On the 3rd/4th rod are the detents to allow overdrive to operate in those gears.
If your gear-lever is rotating, I suspect you may have a wear problem with the remote control and possibly the reverse selector shaft is not moving enough to allow the reverse lamp switch to operate.
You can get to the gear-lever by removing the wooden cover, there is a spring-loaded cap secured by two screws holding the lever in place. It might be worth taking it apart to see where the problem is.

[davidf]

On the subject of the reverse light switch, our switch does not work, and the problem seems to be the plate that is supposed to push the switch in. It jiggles a little when reverse is selected, but it doesn't actually move, and I've a feeling it should slide along and depress the light switch. Reverse selects OK, although the gear lever has taken to revolving around.

This doesn't sound like a manual box. mole42's post describes the function on a manual box - doesn't involve any plate. Could you clarify?

[Tim Proctor]

I'm very confused here. Beneath the gear lever console is a switch, barely accessible. It has what are clearly new wires running to it, a twin-core red and black, and these are connected, somewhere unknown in the loom, to the reversing lights. So it is reasonable to suppose that this switch is the reversing light switch.

But the switch comes on in third and fourth gears, and not in reverse.

Is is out of adjustment, or is a multi-functional switch, because I keep seeing references to "reversing light / overdrive inhibition switch", and reason that the inhibition switch would act on third and fourth gear, as this one does.

Can anyone advise?

[mole42]

It would seem that your 3rd/4th overdrive inhibitor switch has been incorrectly wired to the reversing lights.
There are two switches of identical apprearance. The one you can see is to stop the overdrive activating in first and second gear. The other switch, on the side of the gearshift remote housing, is the reverse light switch.

[Tim Proctor]

This doesn't sound like a manual box. mole42's post describes the function on a manual box - doesn't involve any plate. Could you clarify?

1973 (mk 2) manual with J type overdrive

[Tim Proctor]

It would seem that your 3rd/4th overdrive inhibitor switch has been incorrectly wired to the reversing lights.
There are two switches of identical apprearance. The one you can see is to stop the overdrive activating in first and second gear. The other switch, on the side of the gearshift remote housing, is the reverse light switch.

I suspected as much!

So, two issues, the first to pick up the overdrive wiring to get back to this switch, the second to find the damn reversing switch and pop the red and black onto it.

Does anyone know where the wiring for the OD inhibitor comes from and goes to? I can see the yellow and yellow / purple from the gear stick going into the loom and heading up into the bowels of the dashboard. I think i need to pick u the other end of the yellow / purple and bring it back through the tunnel to the switch.

Would the reversing light switch be under that big plug cover just in front and to the right of the gear lever?

[Tim Proctor]

Reversing light switch found, completely out of sight and reach along the transmission tunnel. It has no wires attached, so it looks like we'll have to at least take the gearbox cross bar off, if not drop the gearbox.

Overdrive inhibitor switch wiring found, the switch had been taken out of the circuit and the two leads simply connected, so no inhibition.

[mole42]

Bad luck, lets hope that you'll be able to fix it easily. ROM 37.27.01 applies.
IIRC you should be able to reconnect the reverse light switch without dropping the gearbox, it's a long time since I've had to do that though. Sliding the hand up the side of the gearbox from underneath isn't an easy job but it might be easier than lowering the gearbox.

Richard