Hitchcocks Forum

Hi all. I have recently acquired a 2001 classic export 'deluxe' and have been getting it ready to put back on the road (not registered for the road since 2006). I have a problem with the rear light after having replaced the lamp unit on the number plate assembly. I have rewired it the same as before, earth and one wire for the brake light and one for the rear light. However both elements light up (maximum brightness) whether I switch the lights on without the brake, or lights off and press the brake (either front or back). Can someone suggest where the problem might lie that sends power to both lamp elements in all circumstances? Thanks

Are you sure the earth really is CONNECTING, as well as screwed on? It would be easy to test: run a wire from the battery neutral direct to the "earthed" part of unit and try again, in order to eliminate this. Good luck, chris

Thanks for the reply. Yes, I am pretty sure I have an OK earth. The indicators work fine and the other lights are ok. I tested the voltage with a multi-meter at the connectors. I get power to both wires (brake and rear lamp) when I either switch on the lights or when I press the brake. I suspect there is some short between the two somewhere back along the loom, but don't know where. rather than trace it all the way back, I was wondering if any 'suspect' areas might be better to look at first?

I just wonder if you have over rotated the bulb Jimmy. If it has twisted too far round in the bayonet socket then both solder end terminals on the bulb will bridge both pins at the bottom of the socket causing both filaments to light whatever light is powered... Some sockets are very loose and some bulb pins are very short thus allowing over rotation.

Some other possibilities: There could also be a short across the rear of connector pins of the bayonet socket. There is a pressure spring at the rear of the connector pin plate enabling it to push outwards to connect to the bulb and this might be shorting the pins. You might be able to pull the paxolin connector out for inspection but to test in situ, simply disconnect the two wires for the stop and tail and test for a short between the two wires.......Just one very less likely possibilty but I'll mention it; IF you have not removed the red plastic lamp cover is that you might have a single filament bulb fitted instead of a dual filament bulb, which will have only a single central solder pin and bridge the two pin socket. Many light units are pre fitted with a bulb and you might be assuming there are two filaments working if you have not had a close look at the bulb but there could be only one. The last suggestion is the least likely however.

Cheers Les. The bulb is dual filament. Both filaments are lighting at once (damm bright when you are checking...). If I remove the whole unit and just check with a multi-meter the connector that comes through the mudguard, then power is at both the lamp and brake wires.

Rear light,brings back memmories,twin filament bulb with offset pins, 10 watts (some 5 watts) 21 watts.You should have two seperate live feeds checking with the bulb out,if both are live then a cowboy has been there,if ok change that bulb.

Go back to the connector under the seat, disconect and test these wires to see if power is at both point here, if so problem is futher forward, if no problem is in the rear wiring or globe. Could be a dud globe

Another possibility is the wiring harness beneath the rear mudguard might have been rubbing on the tyre and worn through the insulation causing a short circuit between the active and earth wires. I have heard of this happening to others when they have fitted a larger tyre, or the harness has just dropped down because loose fitting clamps.

I shall go and test the loom from the seat back to the light first. Thanks for the responses so far, I will let you know progress