Author Topic: Fixing UK Flasher Units  (Read 131 times)

Offline AshimotoK0

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Fixing UK Flasher Units
« on: September 04, 2018, 07:57:06 AM »
Fixed a couple of non-working UK style flasher units last week. The type fitted to UK bikes with the tubular aluminium case. These have an electrolytic capacitor potted into the rear of the can, which   discharges into a coil on the relay part mounted to the circular PCB (brown phenolic PCB type). I suspected that the mode of failure after 50 years, on the examples I had (both UK bikes CB750K0 and CB250SS(K0) ) would be 'drying out' or electrolyte leakage from the capacitor but on the ones I stripped down, these were fine (I tested them by charging them to 12v and then discharging them through a 1k Ohm resistor and measuring the time for the voltage to discharge to 2v) ... I do have a meter which measures capacitance but I suspect the capacitors are greater than 1000uF and too large for the meter.

I then measured the volt drops across the relay contacts with them closed and passing 1Amp DC through them and that was fine too, at less than 0.1v although I did still clean them with contact cleaner strips. The cause of failure, in both units I stripped, turned out to be corrosion/oxidation between the inside of the aluminium can and the tiny brass shim that is attached to the green wire terminal on the circular PCB and earths the can of the capacitor. A quick clean up of the aluminium and the brass shim and they both worked fine.

Interesting that one had simple crimps in the aluminum case to retain the circular PCB and the other had an additional zinc-plated steel ring with three folded over tabs (much neater and easier to get apart). Both were made by ND (Nippon-Denso)

Of course, USA bikes have the rectangular 'Signal-Stat' type flasher unit, which I suspect is just a bi-metallic switch type ... the same mode of operation as the old Lucas units fitted to the original Mini.

I know there are cheapo circular can type ones available (eBay/David Silver etc,.) but I wanted to keep the bikes original.
« Last Edit: September 04, 2018, 08:08:21 AM by AshimotoK0 »
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Offline UK Pete

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Re: Fixing UK Flasher Units
« Reply #1 on: September 04, 2018, 07:59:26 AM »
Wow ash your good fella

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Offline SteveD CB500K0

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Re: Fixing UK Flasher Units
« Reply #2 on: September 04, 2018, 11:00:53 AM »
I'd always assumed that these were bi-metal strips...

What is the source of the clicking noise that you get when they are in operation then?
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Offline AshimotoK0

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Re: Fixing UK Flasher Units
« Reply #3 on: September 04, 2018, 12:05:53 PM »
I'd always assumed that these were bi-metal strips...

What is the source of the clicking noise that you get when they are in operation then?


There is a relay inside of them and the clicking comes from the relay pulling in and dropping out.  The Signal-Stat type is a bi-metallic strip type though.

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Offline Oddjob

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Re: Fixing UK Flasher Units
« Reply #4 on: September 04, 2018, 01:39:54 PM »
Ash your just too clever for your own boots  ;D ;D

With that in mind any idea where to get a very small LED screen which will display numbers, I'm looking at making a gear indicator for my 1300 using the OBD port to get to gear info from but I want it to be mounted inside the clocks like the Suzukis had in the 80s, space is at a premium inside there but there is a lovely little rectangular Honda badge sitting there that I could remove to fit the screen into but of course it's finding a screen small enough for it to fit.

There are some available on E-Bay but they display the numbers vertically and it would need to be displayed horizontally.
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