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MG TD TF 1500 - Electronic No-load (LED) flashers

Has anyone tried using a modern electronic no-load flasher with a positive ground?

In trying to build my taillamp LED units, I'm going to need a no-load flasher. There are plenty around, most for under $20; but they are of course mostly designed for negative grounds.

In researching it seems like some don't specifically require a negative ground; but that may be just a failure to accurately describe the product...

I'm betting that I can use a two wire flasher without trouble, wired into the circuit. But a 3 wire flasher which is meant to have a negative ground may well not work on a positive. So before I buy a few and begin testing, has anyone tried them on a positive ground MG?

Naturally I could convert the MG to a negative ground, but I'm trying to do this so that enthusiasts who want to keep a positive ground system can use it too.

(Another possibility is to use resistors to increase the load on the circuit until the normal flasher operates properly; but that negates one advantage of LEDs... lower draw means lower drain on the system.

Anyway, I appreciate any input, thanks!
Geoff Baker

Just saw this on ebay. be sure to read below. The picture is for illustration only.
John Redman

Hi Geoff I just went out and looked at my TD. I have a "TRIDON" F550 DOT flasher. It works with either polarity and LED's. So that is the answer to your desire to come up with a system that can be used with either polarity.

I assume the "TRIDON" is a brand name. It is only about half as high (long) as the original flasher in a TF. I mounted a sealed beam headlight socket near the horn (TD) and the flasher just plugs into that.

Keep us informed as to the progress you are making.
Bob Jeffers

Thanks, Bob!

I did a little research into the f550 and from what I can see it may not be the best choice for LED apps. It is a positive ground system (on the Tridon website it is shown as being intended for older vehicles) but it is NOT LED specific and furthermore Tridon does not even recommend their use. Lastly, they have a 30 hour lifespan!!

I'm curious, I would be willing to bet money that you have a mixed lamp setup using both LEDs and regular incandescents in front, maybe? With a mix of LED and regular bulbs, you generally generate enough draw to trip the operating circuit of many standard flashers. But on a 100% LED setup, there isn't enough draw to trip the electromagnetic circuit.

Anyway I will keep looking and if I can't find something suitable I'll pick up a f550 and play with it.

I'm beginning to think I should just build the system and then add load resistors until the normal flasher works correctly... we'll see.
Geoff Baker

Geoff - Is there any compelling reason to use an electronic flasher for your set up? Just a plain old fashioned, bi-metal, heavy duty flasher will flash at a set rate, regardless of the load on it and is not polarity sensitive. Cheers - Dave
David DuBois

My interest in LED lighting is to get something much brighter in the rear for running lights and brake/directional lights--a safety consideration. Also, to reduce the current load on the overall circuit. The front running/directional lights can stay incandescent, especially if the current load is necessary to provide proper operation.

As part of doing this upgrade, I'd likely add a high-mount third brake light in the rear, knowing that taken together these combined changes not be increasing the overall current load on the circuit.

Larry Shoer

Geoff Your right in that I have a mixed setup but the flasher clicks with no load at all. It's one fault is that it does not change it's speed if one bulb burns out. But then I am sure that any solid-state flasher you find will have that same fault. The 30 hours is a surprise though, it has been in the car 4 years and so far no end-of-life problems.

Designing a solid-state flasher is not a big deal. Packaging it will be a problem though.

While you are at it why not go for a system that replaces the Lucas pneumatic switch as well as the flasher.
Bob Jeffers

Larry, Custom Dynamics sells light bars you might find appropriate as a 3rd light which might be less visually obtrusive than many. I installed a "Knight Rider" light (yea I know terrible name) on my motorcycle as a 2nd brake light/running light and it worked well.

Dave, I've tried different old fashioned heavy duty ones with LEDs and for whatever reason, they wouldn't work or they worked much more slowly.

Worst case scenario is just that I use the existing flasher and add resistors on the LED circuit until there is enough load to trip the flasher. It's not a big deal.

But I'm going to look at the circuit and see if I can use a two-wire solid state flasher. Because they only have power and load wires, they may well be indifferent to the ground setup. The disadvantage to a two wire flasher is that it will not power the indicator lamp via the third wire; but that can be solved simply by putting the dash lamp on the same circuit as the flasher load wire, thus flashing three not two lamps in the circuit.
Geoff Baker

I have LED signal bulbs and an electronic flasher. Signals work perfectly with the engine not running but flash erratically when running. I have a Dynalite alternator with a heavy-gauge output lead wired directly to the starter switch.
W Worden

If you’re using an electronic DB-10 relay box remove it and try an original Lucas breaker type DB-10. I tried 3 different repop electronic relays and they all were junk. They fed back through their circuitry and causes various turn signal maladies. Once I put a breaker type DB-10 in place I had no more issues.
W A Chasser

I've been using this Electro-Tech system for quite a few years now. I recently converted to all-LED with no problem. I think it will work with any switch, but I bought their column switch because it has a nice look. The system also functions in a hazard light mode.

I have two issues with it: 1) I wish the flash had a higher rate (this may be adjustable - I've been meaning to contact them about it), and 2) I often can't tell if I am flashing or not. My system has a clicking that I can't hear when the engine is running. They now advertise an audible beep. One easy solution would be to use another switch without an auto-return so you could have positive control over it.

Over-all, I am quite happy with it.


J Barry

I converted practically the whole car to LED but I kept the front parking / turn signals with the standard bulbs and the rear to LED for visibility so I could keep the factory FL5 Flasher delay unit. Works great. My car is POS ground.

Frank TF1414
Frank Cronin

As a manufacturer and seller of LED conversions for classic British car lighting, the best flashers I have found are from LiteZupp. They do a variety of configurations of polarity and number of terminals. They are even small enough that they can be hidden inside of an original metal flasher can. I recommend their LXFM3NPG

Lew Palmer
Brittrix, Ltd
Lew Palmer

I have Brittrix 1130 white/amber parking and turn signal lights. I highly recommend them.

J Barry

Lew, is it their LFM3PG ?

Regards, Tom
tm peterson


That one will work ONLY IF you have a positive ground vehicle. The one I listed is not polarity sensitive.
Lew Palmer

Thank you Lew, I will look again

Regards, Tom
tm peterson
Lew Palmer

Thank you Lew!
Regards, Tom
tm peterson

LiteZupp flasher solved all my issues,
and in fact I went with their tail/brake light bulbs as they were brighter than all the others I had tried
J Stone

This thread was discussed between 30/04/2010 and 20/06/2023

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