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MG TD TF 1500 - TF Reversing Light Switch

This thread responds to inquiries made within my previous thread regarding a different style of TF Reversing Light:

http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=thread&access=&subject=8&source=T&thread=201612022019422896

I do have a complete "How To" installation procedure. Unfortunately, it is currently out of arm's reach...too well hidden away somewhere on a HD disc. In the meantime, the following should provide the basic necessary information regarding TF reversing light switch installation. I imagine the TD's is the same.

LOCATION:
Notice the two bump-outs residing on the Transmission Cover driver's side. The reversing light switch is installed into the Transmission Housing underneath the rearmost bump-out.

If your cover is currently off...BONUS !, much of your grunt work is already done & now is the prime time to consider installing the switch.




T.A. Sirp

THE SWITCH:
The optimal switch for this application is the LUCAS 31849A or whatever its modern equivalent may be. The p/n stamped on my switch housing is 31849A 2170.

Also be aware that this switch may be referred to as an "Overdrive Inhibitor Switch".

There are several similar switches out there, however the distinguishing & determining feature of this switch is its contact blade configuration. The 31849A blades extend perpendicularly from the switch outer end, easily eluding any interference contact with the reinstalled Transmission Cover once "wired up".



T.A. Sirp

Are T series gearboxes predrilled to take this switch?
John Quilter

INSTALLATION:
A slotted plug must be removed from the bunghole in which the switch will be installed. Utilize a robust tool that fills & takes advantage of that length of slot so as to not bugger it up (...that hole has been the plug's residence for decades & the plug may not be accommodating for removal).

I made short work of the plug using a rugged slotted driver on a 1/2" drive breaker bar/ratchet.

Install the switch after the plug is removed (the plug can be seen resting on the floorboard directly below the switch in the accompanying picture). Consider using a bit of anti-seize on its threads.

WIRING:
Check the applicable wiring diagram to confirm, however I believe the circuit's wiring code is Green & Green/Yellow. I always make a habit of insulating electrical connections (especially on positive earth to ground British cars).

Run your wires along the existing wiring harness leading toward the rear bumper or other designated Reversing Light location. I inserted both my wires into a protective black electrical harness cover. This cover protects the wires & looks good by making them disappear alongside the existing rearward electrical harness.

Don't be in a hurry to cut your wires to final length before testing your pathway, circuit connections & light. Underneath the vehicle, your perspective regarding certain details may change from your original plan.

TESTING:
After making all your initial connections, energize the system with a supply of 12V, shift the transmission into reverse & light it up! (You did make sure the reversing light bulb was good, right?). Once satisfied with everything, finalize your cuts & connections.

PS: I have a device known as the Power Probe 3 which allows safe testing of electrical operations & equipment regardless of polarity. From the power source, electricity runs thru the device into the circuit. If something is incorrect, the device's circuit breaker will trip instead of something detrimental to the vehicle's equipment. A very handy tool for this type of work.

T.A. Sirp

@ John Quilter: Yes, as mentioned above, on the TF there is a plugged hole ready & waiting. I assume it is the same for the TD. Owners of earlier T-Series would have to confirm those models for you.
T.A. Sirp

The Power Probe circuit tester:



T.A. Sirp

This thread was discussed between 04/12/2016 and 06/12/2016

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