Indicators for a MG TD

Photo 1 showing rear lamp and stainless steel bracket fabricated by Adhoc Engineering along with the replacement inners for the 1130 sidelight on the front.

I love the simplicity of our old T-Type cars but over the last few years I have increasingly felt that sticking my arm out to let other traffic know that I am planning to turn or manoeuvre, was leaving me feeling a little vulnerable. It is fine when the hood is down and the sun shining. Visibility then is excellent but what about when the weather is inclement and the hood and/or side screens are up? When these are in place I find visibility is significantly reduced as well as accessibility to stick out the arm.

My car, like many other MG TDs in the UK, was re-imported from the USA and therefore had an indicator system fitted. However, as it was designed to meet 1950s American regulations it uses the existing white front wing side lights and the red rear brake lights. In short, the brake light doubles as the indicator. The wiring for me as a novice on these things seems complicated with the standard flasher unit wired through an additional relay that controls the indicator by interrupting the brake light if that is in operation.

When I purchased the car this was working correctly but after a year or two something in the system failed and I was unable to trace the problem, so for the last seven or eight years I have happily relied on hand signals. Not seeing any amber indicator lights on the car, the MOT station was content that none were fitted and passed the car every year.

Visiting the MG Restoration Show at Stoneleigh earlier this year I saw that Stafford Vehicle Components had produced a replacement light fitting for T-Types that fits inside the existing wing lamp housing. This fitment offered both white and amber bulbs and seemed like an excellent solution for the front. However there is nothing similar for the rear and looking around at other TD/TFs I found that everyone who had fitted rear indicators lamps had used all kinds of different lights, locations and fitting arrangements.

I decided that I wanted to fit something that was clear, looked period and could if wanted, be fairly easily removed should the car be entered for a Show (not that it ever is!). Also I didn’t want to drill any holes in the car.

The range of lights available on the market is extensive and in the end I went with a chrome torpedo light offered by SVC (+44 (0) 1827 67714) with the view of using the outmost bumper bar bolt as the fixing point. This would allow the lights to be aligned with the central crease in the rear wing and the brake lights.

A local engineering company “Adhoc Engineering” fabricated some stainless steel brackets that would allow easy fitting plus some adjustment to get the alignment just right.

As always, starting one task on an old car inevitably leads to another. On doing a trial run fit on the new rear indicator lights I noticed that the brake lights weren’t working very well and would probably fail the MOT that was due in a few days time. With the help of Brian Rainbow the fault was identified as the inline switch set in the in the hydraulic system. So that had to be replaced first. An easy task but as a precaution I also chose to replace the brake fluid and bleed the system which in turn highlighted a failure of the master cylinder which also required a rebuild or replacement. I digress!

Fitting the front replacement lights was easy following the instructions supplied by SVC. One comment in those instructions was to ensure the front mounting bolt didn’t foul the lower of the two bulbs, which was for the indicator. The first fitting clearly showed the bolt to be marginally too long so rather than pack it with washers I chose to cut off a couple of threads so they fitted perfectly. An additional earth wire was required for each wing lamp and that was easily fixed to the headlamp mounting bracket.

The rear lights were easily mounted thanks to the new brackets and wired through bullet connectors so they could be easily removed if needed. The aim was to use as far as possible the existing wiring loom and Brian had kindly looked at the TD wiring diagram and came up with a set of instructions I could follow.

Both the indicators and brake lights were wired through a relay located in the passenger foot well. As we had already installed a new brake light power supply wire to by-pass the relay as part of the previous investigation in to the faulty brake lights, this job was already done. The rest was fairly simple and a matter of removing the relay and reconnecting the wiring as per the instructions. Great, it should all work, except it didn’t……

I rechecked the instructions and all the wiring and as all seemed correct so it was time to call in the cavalry. Brian very quickly identified that the flasher relay was dead and I had wired the rear lights back to front assuming the black wire was earth and the coloured one live, which perhaps I should have checked out before fitting the lights.

With a new flasher unit and a quick swop over of the wires in the bullet connectors everything worked perfectly.

Colin Hooper

Photo 2 showing the location of the rear direction indicator lamp.
Photo 3 showing the aesthetically pleasing line of the rear direction indicator lamp in relation to the stop/tail lamp.

Wiring Instructions

Instructions to fit standard direction indicators to an MG TD with stop/flash relay installed.

Note: Wire numbers and colours are taken from the TD/TF workshop manual page N.23 “Wiring diagram for cars with separate control and fuse boxes, headlamp beam warning light, foot operated dip switch and provision for flashing traffic indicator lights”. The one exception is in Step 1 where the previous rewiring of my car has left a connection slightly different to that shown in the workshop manual.

Step 1 – Brake lamps

As these are wired through the Direction Indicator Relay as well and need to work independently of it, they should therefore be re-wired first. I suggest checking the operation of the brake lights before starting work to ensure there are no bulb failures.

1.1 Disconnect the green and purple wire (22) from the Stop Lamp Switch and tape over end of the unused cable.

1.2 Connect a length of new wire (ideally green with purple) from the vacant Brake Lamp Switch terminal to the rear of the car, connecting the end to a new double bullet connector.

1.3 Remove the white with brown wire (15) from the right-hand rear light from its current bullet connector and plug the bullet into the new double bullet connector used in the previous step.

1.4 Remove the white with purple wire (14) from the left-hand rear light from its current bullet connector and plug the bullet into the new double bullet connector used in step 1.2 above.

1.5 Test for the correct operation of the brake lights

Step 2 – Front indicators

2.1 Fit the replacement wing lamp bulb holders from SVC as per the instructions supplied with the units.

2.2 A new earth wire will be needed on each wing lamp as the new bulb holders are mounted in plastic fittings and do not earth though the lamp body to the wing as per the old units. I fitted a short length of black cable to the headlamp bracket bolt although it could probably be fed back to the new bolt retaining the wing lamp.

2.3 Test the side lamp operation (these work independently to the indicators).

Step 3 – Rear indicators

3.1 Fit the lamps as per supplier’s instructions or via your own home made bracket.

Step 4 – Wiring the new rear indicators (see Note)

(Note: in this paragraph the wire colour number is given first and Direction Indicator Relay Unit terminal number second)

4.1 Locate the Direction Indicator Relay Unit. (Mine was in the passenger foot well)

4.2 Label all 8 wires on the Relay (in case the wire colours do not match the workshop manual) with the numbers from the relay, then remove the wires from the relay unit.

4.3 Remove the Relay completely as it is no longer required.

4.4 Connect Relay wires green/red (18 numbered 2), white/purple wire (14 numbered 3) and green/blue wire (20 numbered 4) together using a double bullet connector. (I used a 15amp terminal connector block for this and the next actions and to isolate the unused wires rather than bullet connectors)

4.5 Connect Relay wires green/white (21 numbered 6), white/brown wire (15 numbered 7) and green/yellow wire (19 numbered 8) together using a double bullet connector.

4.6 Tape up Relay wire green/purple (22 numbered 5) as it is not now used.

4.7 Tape up Relay wire green/brown (23 numbered 1) as it is not now used.

4.8 Remove the other end of the green/brown wire (23) from Flasher Unit terminal L & tape it up.

4.9 Identify double bullet connector (17) with 3 green wires and remove the green wire that goes to the indicator switch common (middle) connection. Connect this green wire to the vacant Flasher Unit L terminal.

4.10 Connect left-hand rear indicator lamp to the old white/purple wire (14) bullet connector at n/s rear of car. Ensure that the wire from the indicator light is not earthed to the light body.

4.11 Connect right-hand indicator lamp to the old white/brown wire (15) at bullet connector at n/s rear of car. Ensure that the wire from the indicator light is not earthed to the light body.

4.12 Test that all indicators are working correctly.

(Option – fit a 12 volt buzzer in place of/or in addition to the Direction Indicator warning lamp as an audible reminder to cancel the indicators)

Ed’s Note: When I fitted direction indicators to my PB earlier this year I purchased the front sidelight conversion from SVC along with a pair of 1130 type lamps with orange lenses for the rear.

My recommendation would be to always fit a buzzer rather than a warning light. I’ve been in the passenger seat of a couple of cars with a warning light and I’ve had to tell the drivers to cancel their indicator switch on more than one occasion.

One thought on “Indicators for a MG TD

  1. Nigel says:

    Hi there Colin, I am in the process of trying to fit indicator lights like yourself.

    The problem I have is that the contact from the bulb is part of the body and will therefore automatically earth through the body of the casing. Any ideas?
    The lights are INDC011.
    Nigel Fox

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