2003 ST4s Headlight problem !

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BobB

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I came to check on the lights and the pilot light only came on with a gentle tap on the light.
So I thought I should check the main and dip lights.
Neither worked, nor does the pilot light now, but the finger overtake flasher worked the main bulb ok.
I checked all fuses - OK. Then the Bulbs - all 3 were ok.
The light relay clicks when the ignition is turned on.
The rear light and the numberplate light work ok.
The Left Handlebar switch looks ok.

Therefore only feeds and earth connections, but if there was a break in one or both would the flasher work ?

Does anyone have a encountered this problem or have any suggestions as what the issue is and how to fix it ??

Thanks for any help with this.
 
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Sounds strange the flasher works but I guess it bypasses the main light switch. I'd start looking for power after the light switch and work back. ST's commonly have issues with the big connection block, may just be a bit of corrosion in there needs cleaning or the relay has gone lazy (dirty contacts internally) so you can swap with a good one to see if that cures it 👍
 
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Is it the lighting relay that you hear clicking at igntion on? There is also the Main relay and the flasher relay both adjacent to it. The Main relay will click at switch on. The light relay is for high beam and is only activated either when high beam is selected or the pass button is pressed.
Fuse 2 feeds a yellow/orange wire to the lighting switch. In the "Park" position it sends power via a yellow white wire to the ignition switch and hence via a yellow wire to the tail light, parking light and instrument lights. (If the ignition is set to "Park" it powers the parking circuit directly via another circuit from the fusebox). So if the tail light is on the parking light should also be on. I suspect that your parking light issue is different from the main/dip problem, possibly a bad connection or a dodgy bulb.
The Pass button takes power from the same yellow/orange that also goes to the lighting switch the dip switch powers the dip bulb or switches on the main beam relay depending on which is selected. The fact that neither main beam nor dip operates suggest that there is no power to the dip switch input.
The power to the dip switch comes direct from the lighting switch via a yellow/red wire.
So the problem either lies with the lighting switch itself, it's connector to the loom or the left hand switch's connector to the loom.
Only the parking light circuit goes through the 25 pin connector that can cause so much trouble but that would stop the tail light and number plate from lighting too.
I've attached a wiring diagram. It's for the ABS model but it's mainly the same and the lighting circuit is the same.
 

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Barry Hell said:
Sounds strange the flasher works but I guess it bypasses the main light switch. I'd start looking for power after the light switch and work back. ST's commonly have issues with the big connection block, may just be a bit of corrosion in there needs cleaning or the relay has gone lazy (dirty contacts internally) so you can swap with a good one to see if that cures it 👍
Click to expand...
Thanks Derek I will check it out 🤞
 
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Derek said:
Is it the lighting relay that you hear clicking at igntion on? There is also the Main relay and the flasher relay both adjacent to it. The Main relay will click at switch on. The light relay is for high beam and is only activated either when high beam is selected or the pass button is pressed.
Fuse 2 feeds a yellow/orange wire to the lighting switch. In the "Park" position it sends power via a yellow white wire to the ignition switch and hence via a yellow wire to the tail light, parking light and instrument lights. (If the ignition is set to "Park" it powers the parking circuit directly via another circuit from the fusebox). So if the tail light is on the parking light should also be on. I suspect that your parking light issue is different from the main/dip problem, possibly a bad connection or a dodgy bulb.
The Pass button takes power from the same yellow/orange that also goes to the lighting switch the dip switch powers the dip bulb or switches on the main beam relay depending on which is selected. The fact that neither main beam nor dip operates suggest that there is no power to the dip switch input.
The power to the dip switch comes direct from the lighting switch via a yellow/red wire.
So the problem either lies with the lighting switch itself, it's connector to the loom or the left hand switch's connector to the loom.
Only the parking light circuit goes through the 25 pin connector that can cause so much trouble but that would stop the tail light and number plate from lighting too.
I've attached a wiring diagram. It's for the ABS model but it's mainly the same and the lighting circuit is the same.
Click to expand...
Really interesting Derek I will have to go through the system. 🤞
I will see if I can print off the diagram 👍
 
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