Horn, repair or replace

you must mean the one thats behind the rear wheel,fender , battery carrier , airbox and oill tank...

i cant wait to hear some answers on that!

hopefully its the switch and not the horn at all...

good luck to you. i have one with a broken wire at the horn, no easy repair that i know of.

Hello Dave. Ah, the Commando horn ! It has been said that the horn was the first component on the assembly line and the rest of the bike was built round it. My personal vote for that honour goes to the black box air filter. They either welded the frames round those or else put them in flat and blew them up like a balloon.

In order to access the horn you'll have to remove at least rear wheel and rear mudguard which is probably why it's quite common to see Commandos with horns elsewhere. If you're running electronic ignition and the ballast resistor pack is no longer between the coils, you should be able to fit a small 12v horn there.

although the horns are notorious for not working i would check that the switching is in order. the contacts are accessable at the horn itself and could easily be checked with a probe. look under the battery after removing the side cover. could just be an electrical connection problem.

I am sorry but perhaps the mk 3 is different than the earlier bikes i am familiar with? on those the front face of the horn is accessable below the battery carrier. there is a space between the frame, the carrier and the aluminum Zplate. that space is about 1 1/2"x 2". from there you can check theleads at the hornto see if it has earth and power going into the horn. probably can't pull them off or rather put them back on if you do but you could lube them, ha, ha,if Norton hasnt already done so and check with your probe light. bottom lead is power, top is the earth.all my bikes have the roadster style side covers and that may be the difference, isnt the battery in the same place still?. the battery tray is the same for all models so you should have the same opening. it is just behind the rear isolastic on the drive side of the machine.i have the original horn on my 71 still working. it's good idea to sound them now and then to keep them operating.

Previously wrote:

Hello Steven,

I checked the switch by measuring voltage at the in-line connector under the tank and all appeared OK. You say the contacts are accessible at the horn but I have found no way of even being able to see them never mind taking a reading. If I'm missing something I would appreciate your guidance.

Dave F

David,

In one of my earlier posts i mentioned a machine with a broken ground wire. this bike has not run in 30 years, after an accident it was parked untill i purchased it. I just connected a temporary ground to it (thru the hole i have referred to) and the horn is loud and clear! It is a 72 combat i willbe waking up next week after it's long rest.

so dont give up on that horn yet, better to fix it than puta piece of junk between the coils where the condensors and resistorbelong.

regards,

Steven Phelps

Previously wrote:

Hello Steven

I missed your reply of Sunday so only today have I checked the gap you talk of. Perhaps because it is a Mk III and the battery is larger, the gap you refer to is at best about half an inch high. It does enable you to see the terminals with the help of a torch but makes it very difficult to gain access. You have a choice of two of the following at any one time:- torch to be able to see the terminals. A probe of some form to touch the terminal. Being able to see what you are doing!!

With some difficulty I have proven that the horn works when you apply 12V direct from the battery. It works when you apply a wire to the in-line connector under tank and the horn and press switch. It does not work when you apply 12V from the battery to the connector under tank.

Conclusions are that horn works, switch works, and someone has walk off with the piece of wire between the tank block and the horn!

Solution:- Go and buy another horn and find somewhere to stick it on. Mend original set up should I ever be mad enough to totally dismantle bike.

Thanks again for all your help and keep the shiny side up.

Dave F

dave,

on the older bikes there is another connector beyond the one you speak of under the fueltank.on my 72 that connector block is behind the battery and just ahead in the loom where the battery leads branch in.

i am very happy to hear the horn is working. good old lucas! not unusualfor a 35 year old connection to need attention.

The fender does come off fairly easy andit's straitforward, next time you service the rear wheel bearings, speedo drive or brakes, have a go at it.

perhaps you can put a "handle bar horn" on for the government untill you get it fixed? I have a trike bell on my S type and a friend has a squeeze bulb horn on his P-11.

good luck

Steven

Previously wrote:

Hello Steven,

Well done, I owe you a beer. Yes there is another connector box, or in fact a bullet connector behind the battery. It is tucked behind the frame and other things and I hadn't noticed it before. Low and behold, the bullet was pulled out. Push back in, reconnect battery, turn on ignition, press horn button and ... BEEEEP!!

Thanks again for all the help.

Dave F

PS Would you like to purchase a nice new horn?

Thats great news Dave. I am most happy for you. your persistance paid off!

The NOC is certainly a top organization. the forum works in spite of its complexities. Where else could we go?

Rehards,

Steven Phelps