Protecting horn switch contacts against arcing damage

[Nik Rim]

Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and become
intermittent.

Any suggestions on some sort of protective gel I can apply. I've the usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.

 

[ian field]

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...

Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now the
only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical contact
grease, but I only have a battered - nearly empty tube and web searches have
drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one fitted
when I bought the bike, when each brake light switch fails I clean it in
solvent (cellulose thinners) then burn the contacts clean by switching 2x H4
bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those I
fitted has lasted the winter so far, but I'm still thinking of modifications
just in case.

The first suggestion is to use an automotive style relay between the switch
and load, if contact oxidation is your problem, the back emf from the
inductance of a relay coil may produce a spark that punches through the
oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails try it
with new contacts and see if they do any better.

 

[Nik Rim]

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:GFDWm.34874$iW.7396@newsfe30.ams2...

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual contact cleaners etc but nothing for protecting contacts switching
a reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now the
only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical
contact grease, but I only have a battered - nearly empty tube and web
searches have drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one fitted
when I bought the bike, when each brake light switch fails I clean it in
solvent (cellulose thinners) then burn the contacts clean by switching 2x
H4 bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those I
fitted has lasted the winter so far, but I'm still thinking of
modifications just in case.

The first suggestion is to use an automotive style relay between the
switch and load, if contact oxidation is your problem, the back emf from
the inductance of a relay coil may produce a spark that punches through
the oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails try
it with new contacts and see if they do any better.

I've got both WD40 & some teflon spray. I wonder if white silicone grease
would help. Looks like I may have to visit a couple of auto shops.

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day and it's now
15 years old.......

 

[ian field]

"Nik Rim" <querty@kbd.com> wrote in message
news:l8adnTWec9uukbbWnZ2dnUVZ_oednZ2d@westnet.com.au...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:GFDWm.34874$iW.7396@newsfe30.ams2...

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If
I clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual contact cleaners etc but nothing for protecting contacts switching
a reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now
the only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical
contact grease, but I only have a battered - nearly empty tube and web
searches have drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one fitted
when I bought the bike, when each brake light switch fails I clean it in
solvent (cellulose thinners) then burn the contacts clean by switching 2x
H4 bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those
I fitted has lasted the winter so far, but I'm still thinking of
modifications just in case.

The first suggestion is to use an automotive style relay between the
switch and load, if contact oxidation is your problem, the back emf from
the inductance of a relay coil may produce a spark that punches through
the oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails try
it with new contacts and see if they do any better.



I've got both WD40 & some teflon spray. I wonder if white silicone grease
would help. Looks like I may have to visit a couple of auto shops.

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day and it's now
15 years old.......

In theory, any arcing will turn silicone into its dioxide which will
insulate the contacts - silicone is best for repelling water and not much
else.

 

[kreed]

On Dec 18, 1:00 pm, "Nik Rim" <que...@kbd.com> wrote:

Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and become
intermittent.

Any suggestions on some sort of protective gel I can apply. I've the usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.

If you are concerened about them arcing, (which is then pitting,
burning and damaging the contacts) try a 1-2UF poly capacitor across
the contacts.

IF they are switching a logic circuit, or something that draws
virtually no current (not enough to "burn" through any crap that
accumulates), you could try adding a 1k resistor across the load. (ie
- if the contacts switch the load to earth, then add the resistor
between the contact that doesn't go to earth, and 24v supply.

 

[ian field]

"kreed" <kenreed1999@gmail.com> wrote in message
news:38cc9707-de8d-4779-bb7e-c4feb59240cf@u1g2000pre.googlegroups.com...

On Dec 18, 1:00 pm, "Nik Rim" <que...@kbd.com> wrote:
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and
become
intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.


If you are concerened about them arcing, (which is then pitting,
burning and damaging the contacts) try a 1-2UF poly capacitor across
the contacts.

That's a good way to make a capacitor discharge spot welder, put a low value
resistor in series with the cap to limit the instantaneous discharge
current.

 

[kreed]

On Dec 18, 10:52 pm, "ian field" <gangprobing.al...@ntlworld.com>
wrote:

"kreed" <kenreed1...@gmail.com> wrote in message

news:38cc9707-de8d-4779-bb7e-c4feb59240cf@u1g2000pre.googlegroups.com...



On Dec 18, 1:00 pm, "Nik Rim" <que...@kbd.com> wrote:
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If I
clean them up they work well for a week or so and then oxidise up and
become
intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.

If you are concerened about them arcing, (which is then pitting,
burning and damaging the contacts) try a 1-2UF poly capacitor across
the contacts.

That's a good way to make a capacitor discharge spot welder, put a low value
resistor in series with the cap to limit the instantaneous discharge
current.

You probably should add a resistor to make life easier for the cap if
nothing else, but my experience in switching 48v @ 8A DC inductive
loads, there wasn't a problem with this method (capacitor, no
resistor) which was used for years in this application, with hundreds
of switch activations a day.

2uF and The spark was reduced from a substantial "flash" to almost
nothing. Contact burn / pitting and erosion was dramatically reduced.
I considered the very small discharge of the cap into the contacts as
being good for helping keep the contacts clean, whether I was right or
not I don't know.

 

[ian field]

"kreed" <kenreed1999@gmail.com> wrote in message
news:2f5375b1-5e0b-4a4f-8202-74212f3aa5ac@y10g2000prg.googlegroups.com...

On Dec 18, 10:52 pm, "ian field" <gangprobing.al...@ntlworld.com
wrote:
"kreed" <kenreed1...@gmail.com> wrote in message

news:38cc9707-de8d-4779-bb7e-c4feb59240cf@u1g2000pre.googlegroups.com...



On Dec 18, 1:00 pm, "Nik Rim" <que...@kbd.com> wrote:
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had.
If I
clean them up they work well for a week or so and then oxidise up and
become
intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual
contact cleaners etc but nothing for protecting contacts switching a
reasonably large current.

thanks.

If you are concerened about them arcing, (which is then pitting,
burning and damaging the contacts) try a 1-2UF poly capacitor across
the contacts.

That's a good way to make a capacitor discharge spot welder, put a low
value
resistor in series with the cap to limit the instantaneous discharge
current.


You probably should add a resistor to make life easier for the cap if
nothing else, but my experience in switching 48v @ 8A DC inductive
loads, there wasn't a problem with this method (capacitor, no
resistor) which was used for years in this application, with hundreds
of switch activations a day.

2uF and The spark was reduced from a substantial "flash" to almost
nothing. Contact burn / pitting and erosion was dramatically reduced.
I considered the very small discharge of the cap into the contacts as
being good for helping keep the contacts clean, whether I was right or
not I don't know.

Capacitance on its own dramatically subdues any back emf from any inductive
component in the circuit (unless you're lucky enough to hit resonance) so
reducing the voltage rise and the ability to punch through crap on the
contact faces.

For the motorcycle brake light problem I mentioned elsewhere in the thread,
I'm considering deliberately introducing inductance in the series circuit to
cause a "punch through" back emf.

 

[who where]

On Fri, 18 Dec 2009 12:59:30 +0800, "Nik Rim" <querty@kbd.com> wrote:

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day

are you italian? or mustering stock?

 

[F Murtz]

who where wrote:

On Fri, 18 Dec 2009 12:59:30 +0800, "Nik Rim"<querty@kbd.com> wrote:

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day

are you italian? or mustering stock?
I don't use the horn more than once or twice a year, they are

redundant in this day and age. Try this, next time you hear a horn take
note and you will find it has been used illegally or it is after the event

 

[Nik Rim]

"who where" <noone@home.net> wrote in message
news:u96oi5lh0f3nrf30ekkormlmbofccvf0l4@4ax.com...

On Fri, 18 Dec 2009 12:59:30 +0800, "Nik Rim" <querty@kbd.com> wrote:

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day

are you italian? or mustering stock?

Neither, it's a commercial vehicle, needs to "honk" @ each a dozen pickup
points twice per day.

 

[F Murtz]

Nik Rim wrote:

"who where"<noone@home.net> wrote in message
news:u96oi5lh0f3nrf30ekkormlmbofccvf0l4@4ax.com...
On Fri, 18 Dec 2009 12:59:30 +0800, "Nik Rim"<querty@kbd.com> wrote:

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day

are you italian? or mustering stock?




Neither, it's a commercial vehicle, needs to "honk" @ each a dozen pickup
points twice per day.



That is illegal, a horn is only to be used for an emergency.

 

[Mr.T]

"F Murtz" <haggisz@hotmail.com> wrote in message
news:4b2c8bcc$1@dnews.tpgi.com.au...

Neither, it's a commercial vehicle, needs to "honk" @ each a dozen
pickup
points twice per day.

That is illegal, a horn is only to be used for an emergency.

On public roads yes, perhaps his "pickup points" are on private property
though. Then there is a question of noise regulations of course

MrT.

 

[petrus bitbyter]

"Nik Rim" <querty@kbd.com> schreef in bericht
news:l8adnTWec9uukbbWnZ2dnUVZ_oednZ2d@westnet.com.au...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:GFDWm.34874$iW.7396@newsfe30.ams2...

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If
I clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual contact cleaners etc but nothing for protecting contacts switching
a reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now
the only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical
contact grease, but I only have a battered - nearly empty tube and web
searches have drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one fitted
when I bought the bike, when each brake light switch fails I clean it in
solvent (cellulose thinners) then burn the contacts clean by switching 2x
H4 bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those
I fitted has lasted the winter so far, but I'm still thinking of
modifications just in case.

The first suggestion is to use an automotive style relay between the
switch and load, if contact oxidation is your problem, the back emf from
the inductance of a relay coil may produce a spark that punches through
the oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails try
it with new contacts and see if they do any better.



I've got both WD40 & some teflon spray. I wonder if white silicone grease
would help. Looks like I may have to visit a couple of auto shops.

The circuit already has a relay. I think the problem is usage - because of
its application the vehicle horn is used a few times each day and it's now
15 years old.......

Guess replacing the switch by a new one is the most simple and cheap
solution because you will be ready for another 15 years. Even if the thing
does a 150 bucks, it's only some cents a day.

petrus bitbyter

 

[Nik Rim]

"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in message
news:4b2cd8b1$0$9529$e4fe514c@dreader29.news.xs4all.nl...

"Nik Rim" <querty@kbd.com> schreef in bericht
news:l8adnTWec9uukbbWnZ2dnUVZ_oednZ2d@westnet.com.au...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:GFDWm.34874$iW.7396@newsfe30.ams2...

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If
I clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual contact cleaners etc but nothing for protecting contacts
switching a reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now
the only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical
contact grease, but I only have a battered - nearly empty tube and web
searches have drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one
fitted when I bought the bike, when each brake light switch fails I
clean it in solvent (cellulose thinners) then burn the contacts clean by
switching 2x H4 bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those
I fitted has lasted the winter so far, but I'm still thinking of
modifications just in case.

The first suggestion is to use an automotive style relay between the
switch and load, if contact oxidation is your problem, the back emf from
the inductance of a relay coil may produce a spark that punches through
the oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails
try it with new contacts and see if they do any better.



I've got both WD40 & some teflon spray. I wonder if white silicone grease
would help. Looks like I may have to visit a couple of auto shops.

The circuit already has a relay. I think the problem is usage - because
of its application the vehicle horn is used a few times each day and it's
now 15 years old.......


Guess replacing the switch by a new one is the most simple and cheap
solution because you will be ready for another 15 years. Even if the thing
does a 150 bucks, it's only some cents a day.

petrus bitbyter

True - I considered that approach, the vehicle has 6 months to go before it
will be replacee. The steering wheel hub is one of the contacts, replacing
the whole assembly will be $$$$.
thanks

 

[David]

The easiest solution is to just fit an alternative switch to drive the
horn relay - you can buy a push button switch for a few $$ from an auto
parts or electronics supply shop, and wire it in instead of the one in
the steering wheel

If you cannot access the original horn relay just fit another one and
wire it up to the horn and the new switch

Just mount it anywhere convenient, and Marys your aunty

David


In article <-N-dnaKGwvpzQLHWnZ2dnUVZ_sadnZ2d@westnet.com.au>,
"Nik Rim" <querty@kbd.com> wrote:

"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in message
news:4b2cd8b1$0$9529$e4fe514c@dreader29.news.xs4all.nl...

"Nik Rim" <querty@kbd.com> schreef in bericht
news:l8adnTWec9uukbbWnZ2dnUVZ_oednZ2d@westnet.com.au...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:GFDWm.34874$iW.7396@newsfe30.ams2...

"Nik Rim" <querty@kbd.com> wrote in message
news:9pmdnazlvMmkbbfWnZ2dnUVZ_oSdnZ2d@westnet.com.au...
Well it's half on topic....horn switch contacts in a 24V vehicle.

The contacts seem to have lost whatever protective plating they had. If
I clean them up they work well for a week or so and then oxidise up and
become intermittent.

Any suggestions on some sort of protective gel I can apply. I've the
usual contact cleaners etc but nothing for protecting contacts
switching a reasonably large current.

thanks.

For some time I've had a problem with the front brake light switch on my
motorcycle, it is exposed to rain and the contacts corrode - up to now
the only solution has been to carry a spare.

The nearest I've found to a barrier lubricant is Elvolube electrical
contact grease, but I only have a battered - nearly empty tube and web
searches have drawn a blank.

The next best thing is GT85 - its like WD40 but with PTFE.

The previous 2 replacements I ordered fared no better than the one
fitted when I bought the bike, when each brake light switch fails I
clean it in solvent (cellulose thinners) then burn the contacts clean by
switching 2x H4 bulbs with both filaments connected.

When I got down to my last switch, I ordered 3 more - the first of those
I fitted has lasted the winter so far, but I'm still thinking of
modifications just in case.

The first suggestion is to use an automotive style relay between the
switch and load, if contact oxidation is your problem, the back emf from
the inductance of a relay coil may produce a spark that punches through
the oxide layer.

Try it with the filed contacts for as long as it lasts, if that fails
try it with new contacts and see if they do any better.



I've got both WD40 & some teflon spray. I wonder if white silicone grease
would help. Looks like I may have to visit a couple of auto shops.

The circuit already has a relay. I think the problem is usage - because
of its application the vehicle horn is used a few times each day and it's
now 15 years old.......


Guess replacing the switch by a new one is the most simple and cheap
solution because you will be ready for another 15 years. Even if the thing
does a 150 bucks, it's only some cents a day.

petrus bitbyter


True - I considered that approach, the vehicle has 6 months to go before it
will be replacee. The steering wheel hub is one of the contacts, replacing
the whole assembly will be $$$$.
thanks

 

[Nik Rim]

"David" <postings@REMOVE-TO-REPLYconfidential-counselling.com> wrote in
message newsostings-B7DABE.10185220122009@news.bigpond.com...

The easiest solution is to just fit an alternative switch to drive the
horn relay - you can buy a push button switch for a few $$ from an auto
parts or electronics supply shop, and wire it in instead of the one in
the steering wheel

If you cannot access the original horn relay just fit another one and
wire it up to the horn and the new switch

Just mount it anywhere convenient, and Marys your aunty

David

Good idea. Thanks

 

[aussiblu]

Kopr-Shield perhaps; see
http://westsidedelivers.com/kopr_shield.asp I've used it with
success with terminals and alternator slip rings and the like
but not relay contacts. I buy mine from Eastwoods:
http://www.eastwood.com/ but they don't seem to stock it
anymore.

--
Regards
Blue

Remove ZX from email address to reply directly.

 

[aussiblu]

.........or if they are aluminium contacts Alminox perhaps see
http://www.jgthomas.com.au/files/resourcesmodule/@random4765c5acc02ef/1197852611_01.pdf
ALMINOX
" Recommended for aluminium to aluminium bolted or
compression connections. Alminox contains sharp,
conductive zinc granules suspended in a viscous petroleum
base. Under pressure these granules make high pressure
contact points with the parent metal to effect a sound
electrical connection, whilst the base material seals the joint
to prevent further corrosion. Catalogue number ALM325G,
supplied in 325g squeeze tubes. "

--
Regards
Blue

Remove ZX from email address to reply directly.

 

[aussiblu]

The Kopr-shield will work fine on switch contacts - don't know
why I was thinking relay contacts.

--
Regards
Blue

Remove ZX from email address to reply directly.