MOT fail..?

[#1GP200]

About to MOT my Li, upon testing lights i noticed that when i use the horn the lights go completely out.
12v Electronic
12v a.c. horn
No battery
Built scoot from a bare frame so never been on road before
The questions are..
1, Is this an MOT fail ( am thinking it is)
2, What can i do about it.
Cheers in advance.

[essexgp]

Take it you mean the headlight and rear light and that they go off and not dim.

Does the horn actually work?

Do you know what output the regulator is first off, think they are normally 85w

[byron]

unfortunately that's fairly usual for an AC system...

to answer your questions :
1. not if the tester is sympathetic to the age of the vehicle. test the horn with the lights off...
2. check connections, earths etc all good. try an LED rear bulb...? or convert to DC using Wassell tyoe unit as per posts on here...

[#1GP200]

Yeah, lights go completely out, horn working (quite loud as well), not sure about the output but it`s a brand new Ducati
rectifier from a reputable dealer so suspect this is ok.
Could a solution be to fit a battery solely for the horn just to get it MOT`D.

[db67]

hi, had a similar problem to yours on my li 3, turned out it was the metal contact in the light switch behind the the horn button, the horn would work but the contact was shorting out the lights as the button was pressed, i tried repairing it but found it was easier to get a new switch !!!! worth a try, hope this helps, db

[byron]

if the switch is not at fault [these can usually be stripped and made to work] and you do decide to fit a battery for the mot you will have to change to a DC horn

[RICSPEED]

just "accidentally" sound the horn before he tests the scoot

[Toddy]

Sound the Horn before you put your lights on to show the tester

[coaster]

Regardless of the MOT you should sort the problem. If the lights are diming due to the usual reason of there not being enough wattage from the stator to power a decent headlamp bulb AND the rear lamp plus brake light then you will find your headlamp appearing to 'dip' every time you use the foot brake as well as with the horn. I have read of cars pulling out on Lammy riders as thay thought they were being flashed

Byron's suggestion about a LED rear light is a good one, choose the right unit (BGM one is good) and the light output will be the same or better than standard and will stop the diming. Mine was ok even with a 55/60 watt Xenon fitted. I then went the full DC route with the Wasel regulator and would never go back to an AC setup.

[byron]

...your headlamp appearing to 'dip' every time you use the foot brake as well as with the horn. I have read of cars pulling out on Lammy riders as thay thought they were being flashed

that has happened to me more than once, looks like a car is about to pull out in front of you, so you touch the brake slightly, brakelight robs the power from the headlamp, car driver thinks you flashed him and pulls out.... at least you were expecting him to do that...