Headlight woes

[monkeyboy]

This one has me stumped as my electrical knowledge is as good as my rocket science.

Dipped beam is out. There is 12v across the connectors. I've tried several bulbs that I know are working (ie they work in the full beam slot). I can put the bulb in the dipped holder, pull back the gaiter on the connector and measure 12v between the bulb input and the earth on the holder. Still no light though. My question is I can only get the bulbs to light whilst in their holders. Connecting positive to the bulb out the holder and trying to earth the bulb to light it doesn't work. Why not?

What am I missing here? Run 12v in the back of the bulb and earthed through the holders earth connector and the bulb still doesn't light. Am I going mad? I am seriously beginning to think that my bike is possessed

 

[MikeO]

Bad earth? Steptoe will be along in a minute to tell you that there is a large crimped bundle of earth cables near the headstock that is poorly weather-protected and is commonly corroded.

Try putting the bulb in place and then connecting a wire from the earth (anywhere in the shroud) to the negative terminal and see if that lights it up...

Mike

 

[monkeyboy]

Bad earth? Steptoe will be along in a minute to tell you that there is a large crimped bundle of earth cables near the headstock that is poorly weather-protected and is commonly corroded.

Try putting the bulb in place and then connecting a wire from the earth (anywhere in the shroud) to the negative terminal and see if that lights it up...

Mike

Weird thing is I measure 12v using the earth on the holder - maybe I should be measuring amps instead to see what's drawn. I flippin hate electrics.

I'll run a wire direct to the neg terminal in the week and see what gives. I replaced the main wiring loom a couple of years ago but obviously all the front wiring is on separate connected subsections and I left them as they were. Maybe thats the problem. I'll try re-earthing.

 

[Timolgra]

The bulb may not be making a good contact, scratch both the bulb and holder terminals to clean them.

 

[monkeyboy]

The bulb may not be making a good contact, scratch both the bulb and holder terminals to clean them.

I've tried some brand new bulbs and I'm getting 12v from the bulb and through the shroud so hopefully the contact is fine but it won't hurt to scratch it up and make it better. I'll try anything!

 

[MattW]

These are symptoms of a bad earth - you can measure 12v at the terminals but there's virtually no current and the lamp won't light. As previously said, run a temporary independent earth from the bulb holder back to the battery and see if it works. If it does, step the earth back down the loom from the bulb holder to identify where the fault lies.

As others have said, my money is on the big headstock earth bundle - find it in the sheathing (Steptoe has detailed where it is in other threads - have a search) and see if it's a big blob of green fur.

 

[Ian J Hartley]

It might help if you listed the bike your having problems with. On later R1150GSA, those with servo brakes the wiring was modified so that the low beam and instrument lights are protected via fuse 8.

However, the wiring for the low beam, high beam, front indicators and horn all form part of the main bike loom, including where necessary the earths.

The headstock loom that is being mentioned is a separate loom, which has all the instrument light wiring, including all the warning lights, together with their earths.

 

[monkeyboy]

It might help if you listed the bike your having problems with. On later R1150GSA, those with servo brakes the wiring was modified so that the low beam and instrument lights are protected via fuse 8.

However, the wiring for the low beam, high beam, front indicators and horn all form part of the main bike loom, including where necessary the earths.

The headstock loom that is being mentioned is a separate loom, which has all the instrument light wiring, including all the warning lights, together with their earths.

2002 1150gsa. As I mentioned, I replaced the loom a few years ago so must have replaced those connections. I just can't remember. I'll run it though direct to earth at the weekend then track the problem back. I can just do without it at the moment as I've had 2 bikes gone down within a week and I need this one on the road.

 

[Ian J Hartley]

The wiring at the low beam connector. Are the two wires:-

A. brown and green/blue with yellow dot

Or

B. brown and white/yellow

If it's A they your bike has likely got a modified main wiring loom, same as the servo bikes.

 

[warmshed]

Assuming the bulb is good, If you measure 12 volts across the terminals of the bulb holder with the bulb inserted and it does not light it can only be the bulb holder contacts. Either from the earth and battery voltage where your meter is, to the holder or where the bulb terminals contact the holder terminals.