1990 K75Rt Horn Blows in the Rain

[beemerboy]

I've had several bouts of this problem over the last two seasons. When it rains or I take the bike to a carwash the horn will blow on its own. Sometimes a quick flick will stop it but other times it just keeps blowing until I shut the bike off. For the last week it wouldn't work at all but today I took it to the carwash and on the way home, off it went. It has the unusual ability to detect another vehicle in near proximity before letting her rip. Very embarrassing. One day a few weeks ago I ducked into a coffee shop to get out of the rain. Once i headed into rush hour traffic the horn blew with incredible gusto.

Any one know what is going on and how to correct it? The switch unit cannot be sealed very well. I never had a problem like this, even on my old Bonneville with Lucas electrics. I'm just glad it didn't do this on the day of my road test last year- a day of wind driven rains.

BB

 

[98lee]

So do you ride your bike or push your bike through the car wash? The suds must make it hard to see.

Sounds like you got way to much water where it's not supposed to be. High pressure water is never a good idea around the electrical parts of a bike. You've probably filled up the left switch gear assembly. Take it apart and clean and dry it out.

 

[beemerboy]

Lee, very funny. I like that image though.
I just use the wand wash and I don't put it very close to the electrical bits or instruments. Never closer than 2 feet and not for long since they don't really get dirty. It's more overspray than direct flow on them. Also, as I mentioned, this also happens in the rain and it doesn't have to be a torrential downpour for it to occur.

I also don't understand why the last time, after it dried up, the horn didn't work at all - for two weeks- until washing today when it goes off on it's own. Are the contacts straight brass that they corrode and don't make contact? I guess, I'll have to pull it apart and see what gives. I still say it can't be sealed very well if washing and rain get inside and screw things up.
BB

 

[72r60/7]

Rain Horn

I suggest when/if you take the switch apart the first time (or every time), do it inside a clear plastic bag.
Boing ! Boing !

Charlie

 

[pauls1150]

Does the K75 use a horn relay? Maybe the water/corrosion/whatever is happening inside the relay or in the socket that it plugs into.

Meanwhile, after a wash, use high-pressure air to blow the excess water off...

And do you take off your helmet while in the wash?

 

[beemerboy]

Thanks for the heads up and the idea, Charlie.
Sounds like you've been down this road before. Any other ideas about how to keep the tiny bits where they belong? The problem with stuff like this is that you can't see or get a photo of what's inside before you start. I just repaired a switch on our washing machine that was fairly simple but took a lot of thinking to figure out where it went and to get stuff to stay where it belonged. How the factory assembles these in volume at high speed is still a mystery.

BB

 

[beemerboy]

Paul, I just leave the helmet on to get off all the bug guts. Nah, actually I leave it outside with my jacket. I hadn't thought of the relay but it seems to be the switch since jiggling it will shut it off for a short time. Blowing air is a good idea at the car wash but doesn't help me in the rain. Actually it won't help until I get home to my compressor. Meanwhile the horn is blowing through town. Maybe I should hook up an engine driven compressor with a dedicated line to the guts of the switch so I can blow it out while riding ; )

BB

 

[PGlaves]

Spray a good alcohol based contact cleaner into the switch and work the horn button repeatedly. You can remove the switch from its mount (1 little screw) without taking it apart. It is easier to get the cleaner into the horn switch from the mount side.

 

[beemerboy]

Thanks, Paul G.
Is there any way to seal this unit up a little better?

BB

 

[PGlaves]

Thanks, Paul G.
Is there any way to seal this unit up a little better?

BB

Not really. You can probably work a little dielectric grease near the contacts from the mount side. The contacts are on the side and contact with a sliding motion.

Crud and corrosion also attract and hold moisture which may be the root of the problem here. There are lots of K75s running around in rain that never had this issue. I would clean it up and see what happens.

 

[beemerboy]

Agreed. Clean up and lube. Question on this: I and several others disagree on the purpose of dielectric grease. I always thought DE grease was to prevent electrical conductivity. Others disagree and say it supposed to improve conductivity. When you mention sliding contacts I'm thinking that DE grease does reduce electrical conductivity since when they slide the grease would get pushed out of the way. I could be wrong. I was once before in 1985.

Paul, I gather you don't recommend taking the switch apart. You keep mentioning that it can all be accessed through the hole. I'd like to tear it down just to get all the corrosion and crud out. But if it's a pain then I'll just do the "fire in the hole" method.

Also, I took the scooter for a run today and the horn works in the dry! (Well in the humidity). Maybe that's the sweet spot: enough humidity for it to work but not so much water that it auto plays.

BB

 

[PGlaves]

Agreed. Clean up and lube. Question on this: I and several others disagree on the purpose of dielectric grease. I always thought DE grease was to prevent electrical conductivity. Others disagree and say it supposed to improve conductivity. When you mention sliding contacts I'm thinking that DE grease does reduce electrical conductivity since when they slide the grease would get pushed out of the way. I could be wrong. I was once before in 1985.

Paul, I gather you don't recommend taking the switch apart. You keep mentioning that it can all be accessed through the hole. I'd like to tear it down just to get all the corrosion and crud out. But if it's a pain then I'll just do the "fire in the hole" method.

Also, I took the scooter for a run today and the horn works in the dry! (Well in the humidity). Maybe that's the sweet spot: enough humidity for it to work but not so much water that it auto plays.

BB

Dielectric greas does not conduct or improve conductivity. But it can help to keep moisture and corrosion away. The sliding motion wipes the grease off the contacts. Thus, why I would try it given your issue.

Taking the sitch apart is risky and not necessary. It is simple to flood the contacts with cleaner. Use it and compressed air if you feel the solvent isn't sufficient.

 

[98lee]

Taking the switch apart is risky and not necessary. It is simple to flood the contacts with cleaner. Use it and compressed air if you feel the solvent isn't sufficient.

I very rarely disagree with Paul, but in this case I would say; It depends. If you are moderately mechanically inclined, it is pretty simple and straight forward to disassemble. You will get a better and more definitive picture of the condition of the switch.

The left switch assembly is pretty simple, a few screws, a couple of springs and the buttons with contacts.
If you pay attention during disassembly, it's pretty easy.

If you're still hesitant, I could post pictures maybe tomorrow or Tuesday.

 

[beemerboy]

Hi, Lee.
I've done some fairly extensive mechanical work: rebuilt tranny's and engines- gas and diesel- car, MC, trucks. All the regular brakes, water pumps, u joints etc. I'd appreciate a look at the switch without it's clothes on. I've learned over the years that it never hurts to see what you're going to see before you dismantle it. Besides, I'm a glutton for mechanical punishment and the pix would convince me to get into it further than I other wise would.

BB

 

[Bobmws]

Disassemble the switch inside of a box, gives you a better chance of finding those little springs when they go flying! Credit for this tip goes to Don Eilenberger.

 

[dbrick]

I think disassembly inside a clear plastic bag would be easier.

 

[98lee]

Here's the Pics: http://forums.bmwmoa.org/showthread.php?81859-Disassembly-of-Headlight-Switch

If you take it off the bike (a bit of work), you won't need a bag or box.

If you do it on the bike, you save the removal labor, but make it much harder to clean. Make sure you protect your paint if you decide to try and do it on the bike.


Let us know how it works out and which way you did it.

 

[Omega Man]

Here's the Pics: http://forums.bmwmoa.org/showthread.php?81859-Disassembly-of-Headlight-Switch

If you take it off the bike (a bit of work), you won't need a bag or box.

If you do it on the bike, you save the removal labor, but make it much harder to clean. Make sure you protect your paint if you decide to try and do it on the bike.


Let us know how it works out and which way you did it.

Nice
OM

 

[beemerboy]

Thank ya, thank ya'all very much.

BB

 

[beemerboy]

Had a look at the pix, Lee.
Very clear and concise. Now I just need to screw up my courage, grab a plastic bag and have at it. I also need to replace tires and a few other odds and ends. I'll get back to this thread when i get it done (or, more likely, have questions).

BB