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MG Midget and Sprite Technical - Frogeye Flasher Unit

After fitting a new wiring loom to a 1958 Frogeye (converted to negative earth) all the indicators, lights etc are working well except one frustrating issue, the dash indicator warning light is not working.

A new flasher unit was ordered but after fitting only around 6 volts was being supplied to the dash bulb insufficient to light it, the indicators flashed correctly.

A second flasher unit was ordered from another supplier, all worked OK including the flashing dash bulb but it continued to flash when the indicators were turned off! This was later found to be for positive earth vehicles only, although no mention on the ordering website.

After collecting a third from a different supplier this was also found to be for positive earth vehicles but they swapped for an alternative electronic flasher unit for negative earth but this requires an earth and the wiring changed which I would rather avoid.

Surely such a simple job should not be such a problem, am I missing something obvious as I have never experienced such issues with the negative earth midget.

Tim Lynam

Tim

Any chance of a link to the flasher units you've been fitting?
Dave O'Neill 2

Thanks Dave,

The flasher unit which was found to be for positive earth is, https://www.ahead4healeys.co.uk/-FLASHER-UNIT---SCREW-CONNECTOR-id12247.aspx

Another was https://www.autosparks.co.uk/electrical-components/lucas-3-pole-flasher-relay

The electronic flasher unit which requires an earth and a change in wiring is https://www.autosparks.co.uk/electrical-components/lucas-3-pole-flasher-relay





Tim Lynam

The link for the electronic flasher is wrong. It's the same as the link before it.

None the less, I have an electronic flasher for my Frogeye that had the same connections as the mechanical type and didn't need a separate feed. It works just fine.

Rob
MG Moneypit

Rob,

Yes sorry the electronic flasher is https://www.autosparks.co.uk/electrical-components/12v-electronic-flasher-unit

Connected the same way as the original flasher unit I am only getting around 2 volts at the dash bulb, so not enough to give more than a very slight flicker, but interesting to hear yours works fine.

Tim
Tim Lynam

Tim
You have a new member - Steve Smith. Steve is an rtd auto electrician. Your gain is our loss. Ian Cooke will have his contacts. Steve will sort it in no time.
Alan Anstead

Cheers Alan,

Yes I have been in touch with Steve regarding the Notts & Derbys group and will be good to have him on board. Im sure he’ll be made welcome.
Tim Lynam

Tim

I have some used 3-pin flasher units, if you want to try one?
Dave O'Neill 2

Tim
The older thermal flasher units, such as Dave is offering you, are not polarity sensitive. I converted my Frog to negative earth and the older flasher unit used when it was positive earth works fine. How did you measure the dash bulb voltage?
Bill B

Dave,

Yes that would be a great help thanks, it would be good to find out if it’s the new flasher units or maybe something else is at fault.

Bill, the measurements are just approximate taken with a basic multimeter (not digital) at the live terminals at the flasher unit and live point at the bulb. Thanks for confirming the old units were not polar sensitive.
Tim Lynam

Tim
It's unlikely you'll measure 12v, especially with an analogue meter, as the voltage is switching on and off continuously so the meter measures the average voltage over a period of time which is somewhere between 0v and 12v, maybe less than 6v.

When the dash bulb continued flashing it sounds as if you had it connected to the wrong terminal.
Bill B

When I changed my mk3 Sprite to negative earth I bought a new flasher from Moss which wouldn’t fit in the same place as the original because it was too long, so I refitted the original one. It’s still there working perfectly after 60 years.
b higginson

It's likely the bulb socket on the dashboard has 2 wires, one live from flasher and an earth. Likely the socket needs cleaning or the earth lead has a slight resistance to earth. Beware though the plastic has a tendancy to disintegrate due to age.

Rob
MG Moneypit

technology has moved on a bit - not voltage drop with one of these!


S Macfarlane

There is pnly one wire to the flasher bulb on a frogeye. The outer metal case earths against the metal dash. It does happen that the earth is poor and the light will not flash. As mentioned though the plastic insert which holds the bulb holder to the Chrome ring on the dash front can disintigrate
Bob Beaumont

Bob, the old original metal outer case which the bulb holder fits into is no longer with the car and has been replaced with it's modern replacement which is plastic, the original bulb holder does only have one live wire but cant be used with the plastic holder.
The new replacement bulb holder does have an earth connection.

Some of the old and new flasher units have been tested and found to be faulty, hopefully a solution will soon be found.

Thanks for everyones comments.
Tim Lynam

This thread was discussed between 05/11/2025 and 07/11/2025

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.