Electrical problem, advice please

[williamcorke]

I'm hoping someone can help me with remote advice to solve an electrical problem with the S6 B20.  

The car was fitted by a previous owner with an 'interruptor' sytem for the indicators, which uses the rear sidelight / running light as an indicator - so no additional light units need to be added to the car.  A fairly standard modification, as I understand it.  It's worked fine for years; until now...

Things are OK indicating right - arrow tell-tale on dashboard flashes, rear light flashes, ameter shows a few amps of negative deflection.

But try to indicate left and there's no light on dash or at the back of the car: but... the ameter flicks to full negative at the frequency you'd expect from the indicator.

Could be a short to earth somewhere (though the fuse hasn't blown).  But where?  

I took the lid of the 'interruptor gubbins' box.  It seems to have an arrangement of 4 relays joined to each other by mysterious wires!  Perhaps one of these is malfunctioning?

Any ideas of what to test next would be much appreciated.

[Richard Fridd]

Hi William,depending on the design,perhaps the  electromagnetic coil  in a faulty relay is drawing current as indicated by the ammeter but the relay contact is not interupting voltage to the rear bulb. If the dash lamp is in parallel with the feed to the relay it will still illuminate.best regards richard

[andyc]

A short to earth on the light's live feed i would think should cause a problem with the rear sidelight/running light does it work as a normal sidelight/running light i.e only faulty on the indicator? Then as Richard says it could be a coil in one of the relays.
Andy

[williamcorke]

Thanks for thoughts.

Left rear light works -  both sidelight and brake - so I suspect the interruptor unit is at fault.  Anyone know where to buy another one?  I'll be needing one for my B10 anyway, so won't be wasted if the problem turns upto have been something else.

[ColinMarr]

William, I have just sent you an off-forum email, which will hopefully guide you to a real expert.

Colin

[Kevin MacBride]

On my car, I removed the internals of the original flasher relay. I re-wired it and used the existing wiring arrangement, and linked it to a 'modern' 3 pin relay. I actually used a standard Fiat part (I'll check the part number). My car had tail lamp from a trailer, oval kind with seperate brake/stop and indicator lens. I re-fitted the original type lamps, using a single bulb, so now I have indicator/stop and tail as per original.
I'll dig out a wiring diagram, and see if I can scan and post it up here.

[ColinMarr]

I am a bit amused by this quest for originality. When I did my 6th Series B20 about 25 years ago the last things I wanted were those little oval rear lights! Having driven behind American and other cars with this arrangement and seen how dangerously confusing they can be, with stop-lights, indicators and rear-lights all going off at the same time! I elected to fit rear lights that at least separated indicators from braking. I chose units from an Alfa SZ, which were also fitted to other cars of this period and were I think a period option for late B20s. I reckon they looked good too.

Colin