860 GT Flasher unit and two tone horn relay - Ducati.ms

900SSDesmo · Jun 10th, 2011, 11:45 pm

Hello,

I have a 75' 860 GT that I just put together and their are two oddities in the wiring that I don't know if you fix, replace or update? One one is the flasher unit and the other is the horn relay. When I put a battery in the bike the horn does not work, but the switch is good and the horn will work when I put 12 volts directly to it. Also while sitting with the ignition on - the horn begins to get hot! I expect the horn relay is bad and don't know if you update it and loose the two tone feature or are these old units repairable?

Signals don't work and I checked the switch and the wiring and they all check out. So, same deal: is there any reason to save the old flasher unit, or does anybody know of an alternative?

Thanks in advance

DesmoDog · Jun 13th, 2011, 9:48 am

Quote:

Originally Posted by 900SSDesmo

Hello,

I have a 75' 860 GT that I just put together and their are two oddities in the wiring that I don't know if you fix, replace or update? One one is the flasher unit and the other is the horn relay. When I put a battery in the bike the horn does not work, but the switch is good and the horn will work when I put 12 volts directly to it. Also while sitting with the ignition on - the horn begins to get hot! I expect the horn relay is bad and don't know if you update it and loose the two tone feature or are these old units repairable?

Signals don't work and I checked the switch and the wiring and they all check out. So, same deal: is there any reason to save the old flasher unit, or does anybody know of an alternative?

Thanks in advance

I've got a late '74 750 GT which has very similar wiring to the 860. Or at least it did from the factory... I completely rewired it but that was a few years ago so I may be little fuzzy on the details.

Anyway... you can use pretty much any flasher relay and it will work fine. I picked up a generic one from the local autoparts store.

Same deal with the horn relay. I'm using a generic one which now resides under the seat. I don't see why using a new relay would defeat the two tone horns? All the relay does is flip a switch - you only use it so the switchgear doesn't see the amps that the horn(s) draw. The switchgear flips a switch in the relay, which then routes the power to the horn.

I'm nowhere near on expert on electrickery, but I'm wondering if you're problem with the horn may be the wiring? The switch for the horn is on the ground side of the circuit, not the power side. What this might have to do with any of your issues I dont know, but it did have me confused for a bit.

wdietz186 · Jun 14th, 2011, 10:07 pm

If you haven't done so already,take apart all of those gang plugs in the harness[for the bar switches and the other connectors] and clean the green fuzz that is probably growing between the terminals.That should get the components to work. Ultimately you will find that the harness is a piece of shit and rewiring it with heavier gauge wire, relays,and Jap switchgear will be the only way to get lights brighter than a firefly or a horn louder than a bee fart.

900SSDesmo · Jun 18th, 2011, 1:41 am

Sure enough the gang connectors were grungy and I did not have a ground at the turn signals in the rear. Tried a new horn relay and it made no difference on the horn. Turned in the screw on the back of my new Voxbell horn and bingo - the horn works. I agree that the wiring appears to be substandard and have begun replacing it. I want to keep the original switches so it looks correct. I only had to buy two sets to piece together a working pair... and these were supposed to be NOS. Odd but when I opened one of the switches up, all of the contact plates were in one switch and the others had none! Obviously it would have never worked.

confusa · Jun 25th, 2011, 5:12 pm

Supposedly, per the DIOC newsletters, that two tone relay is subject to failure and should be disconnected. I just went through the wiring on my GT, and the horn relay is indeed bypassed. Only one position on the switch on the dash works, essentially just there to complete the circuit.

860GT · Jun 26th, 2011, 5:36 pm

Unless you're doing some Concours restoration, it is not worth trying to get the two-tone horn working properly. When my 860 was brand new, I could barely tell the difference in tone, even when it was working properly. Not much of a horn, even on loud.

DesmoDog · Jun 27th, 2011, 10:27 am

Quote:

Originally Posted by DesmoDog

Same deal with the horn relay. I'm using a generic one which now resides under the seat. I don't see why using a new relay would defeat the two tone horns?

Ahh... now it's all coming back to me. I had forgotten there was a switch on the dash for a city and country horn or whatever they called it. I was thinking two tone as in two different notes at the same time which is what I replaced my stock horn with.

Yeah... I replaced my dash with a Sport dash, no more horn selector switch. As for loud, I tested mine. Indoors. With a lot of concrete around and my ear about two feet from them when I made the connection to the battery. They struck me as being VERY loud...

captpaul · Jun 27th, 2011, 8:56 pm

I've had my 860/900 gts for 25yrs,(1978)
Every one tells me the stators all ways go bad,poor design . But one guy told me that 75& 76 had lemon stators and ducati corrected the problem on 77 & 78 is this true?
Do I have to convert it to a paso system, or 78 stators ok? I would appreciate your opinion. Capt Paul