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MG MGA - Turn Indicator Light

Catching up on some general jobs as my knee is shot and I cannot walk more than a couple of hundred yards at the moment. So it's stand still/sit down jobs around the car to keep me occupied and out of the heat.

My dashboard indicator light does not illuminate - it used to until a few weeks ago. Checked the bulb. It seems fine. Meter shows leccie going through it okay. I then put the meter on the bulb socket and that shows leccie pulsating through it at 12 volts in sympathy with the lights on the 4 corners. So, I'm a bit stumped. I am no expert on electrics and meter readings. I can only imagine high resistance somewhere in the line (or bulb?) but how do I check it with the meter? It's beyond my knowledge level. The earth line is connected to other bits that are working ok. I would add that I soldered in the additional earth line rather than rely solely on the holder earthing through the dashboard.

The bulb is the standard screw in 12v 2.2W.


Steve
Steve Gyles

Checked the bulb on my spare battery. Working. Earth system fine. Just check. Problem appears on live feed. Got the hang of my meter a bit more. Seems I only have a 5 volt feed. What next? I have a modified system on my 1500. I separated the indicators from the brake lights.
Steve Gyles

I am guessing there is a poor connection somewhere. So you probably need to trace the circuit back to the flasher unit, and then to the fuse ( if yours is (or was) a 1500, you will probably also have a relay unit).
Circuit diagram on Barneys site but you probably already have one.
That should highlight which part of the circuit has the problem.
Graham V

Graham

On the basis that the 4 flashers are working fine I have very few things to check. It is a single cable from the indicator light to the P terminal on the flasher. I will check that output. My suspicion is an internal resistance on that part of the Flaher unit.

Steve
Steve Gyles

Looks like a duff flasher unit - again.

Put the meter on the terminals in turn. 12v in; 10v pulsing out to indicator switch; 5v pulsing to indicator light on dashboard.

Modern rubbish. Best supplier of a reliable unit recommendations?

Steve
Steve Gyles

Pleased you have the answer. I guess another option is to get a lower voltage bulb, but that’s a bit of a bodge
Graham V

Graham

Looking through the archives loads on duff flasher units including from me with similar issues in 2015. Mine has SFP100 on it. Seems to come up as a Lucas part. That accounts for it. Prince of Darkness. EBay full of them. Must be better somewhere.

Steve
Steve Gyles

When I switched to LED lamps for the brake and turn signal lights I also switched to an electronic flasher. It's been doing well for several years now.

One semi-odd thing though. I recently switched out the panel indicator lamp for a green LED because the incandescent was very dim. Now, the panel indicator continues to flash for 20-30 seconds after the turn signal has returned to the center (off) position. The turn signals don't continue to flash, only the panel indicator lamp. Curiouser and curiouser.

Jud



J K Chapin

I don’t know whether most others do this so if you don’t I suggest you carry a copy of the wiring diagram with you tools. Assuming your car is correctly wired knowing what wire should be what colours can be a big bonus.
Paul Dean

Steve

The modern equivalent flasher units are poor quality. See if you can find an Original Old Stock one. The Prince of Darkness probably only came into being in the 1970s on Jaguars.

As an ex Lucas engineer I would defend the quality and engineering that went into a lot of their products.
John Francis

I've never understood this Prince of Darkness label when the items from many decades back continued to work in use for many decades. To me it often seems to be some kind of insular US thing and/or to cover careless vehicle owners, mechanics and auto electricians. That's not to say British car manufacturers didn't sometimes throw an uninsulated screwdriver into the works.

Lucas is just a brand name now with Elta and SMPE that I can think of, with different colour labels and boxes for different items and brand names now.

It's hard to know with the major usual classic car parts supplier suspects how long their stock lasts to if and when batch quality might improve or not

As I've had good service and products from Classic Car LEDs I reasonably comfortable (when can you ever be certain) to recommend their flasher units that work with incandescent bulbs too. - https://www.classiccarleds.co.uk/collections/indicator-relays-electronic
Nigel Atkins

I agree with Nigel’s first two sentences concerning the origin of the “Prince of darkness” label, and with John’s statement about original-Lucas products.

Having owned six MG TCs over a number of decades, usually two at once, and today having a single TC and an MGA, I have experienced only excellent performance from original-Lucas equipment. This does require that the car’s wiring is in good condition and the original-Lucas items are maintained and adjusted correctly.

My MGA’s original-Lucas flasher, probably between 30 and 60 years old, failed a couple of years ago while we were in Germany – an amazing product life – and I had to resort to a new-Lucas-branded item from the travelling spares in the boot. On return home I was able to buy an NOS in box original-Lucas flasher, but this did not flash at the correct rate so could not be used. I’m still using the dodgy “new-Lucas” flasher in the MGA, with another as a spare in the boot.

I don’t use electronic ignition. We do long trips in both cars and I wish to know that I can check spark and points if ever necessary, using on-board tools and spares. (We returned in June from our sixth MGA trip England to Italy.) Both our TC and MGA have original-Lucas distributors, rebuilt by Martin Jay with correct advance curves. The TC curve is for its supercharged XPAG engine.

My firm preference is for the reliable original-Lucas products maintained in correct condition, the original wiring circuit, no extra fuses or relays, and no modern electronics in the distributor or voltage regulator, just the original items in correct condition and adjustment.

The electronic flasher mentioned by Nigel looks like a possible solution to the new-Lucas flasher dilemma.

Mike
M D Card

John

Lucas must have been an enormous enterprise employing thousands. I recently saw a detailed video of the Armstrong damper factory, do you know if a similar exists for Lucas?

Cheers
Dave
Bolney Coupe

There's a short and not very clear video of Lucas dynamo production at

https://www.youtube.com/watch?v=JnbkTgJwqyI

Malcolm
Malcolm Asquith

Reverting back to Steve’s problem, it looks like those flasher units recommended by Nigel might be a good choice. Rather than relays, they are electronic, so there should be no worries about moving parts, internal contacts, over heating etc., so less to go wrong.
Graham V

Interesting comments about Lucas. My next door neighbour was telling me yesterday that his dad worked in Jaguar quality control (or equivalent back in the 50/60s). They had very bad experiences with Lucas bulbs at the time; a large number of them were not achieving the specified brightness. They discovered that Rolls Royce used the same bulbs but had no issue. The Lucas top brass was duly summonsed to a crisis meeting. i.e. sort it or we take our business elsewhere. It transpired that Lucas did their own quality checks and graded their bulbs before despatch. The best ones went to RR; the next to .....etc.

Steve
Steve Gyles

My comment on this issue may be relevant, I hope. I have experienced various Lucas (and more modern “Lucas” labelled) flasher unit failures over the years. A couple failed somewhat similarly as Steve has implied at the beginning of this thread - the main car indicator lights flashing ok but not the dashboard “jewel” bulb. (I hope that’s the correct interpretation Steve). On opening up those failed flashers, from memory, the culprit was the contact which energises the dashboard bulb whilst the other contacts functioned ok. After multiple failed flashers I finally succumbed to modern technology and installed a cheap electronic flasher unit from eBay, mounted in a Lucas “can” with original connection terminals and indistinguishable from an original electromechanical unit. That’s been working well for some years now.
Bruce.
Bruce Mayo

Success. All sorted. Cockpit bulb working. In fact it has never been brighter. I bought the original MGA style Lucas flasher.

Steve
Steve Gyles

This thread was discussed between 12/08/2022 and 18/08/2022

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