Honda-SOHC
SOHC.co.uk Forums => Anorak's Corner => Topic started by: AshimotoK0 on September 04, 2018, 07:57:06 AM
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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.
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Wow ash your good fella
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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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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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