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05-22-2019, 06:51 PM
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#1
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Mini-Skoolie
Join Date: Apr 2019
Posts: 20
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5 steering wheel buttons but only 3 wires out?
Hi. There are 5 buttons on my steering wheel: doors off/on, flashers, red, horn. However, there are only 3 wires leading away from the steering wheel. Could anyone explain? Thanks
IC CE300 2005
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05-22-2019, 07:53 PM
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#2
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Bus Nut
Join Date: Sep 2017
Location: Damascus, OR
Posts: 681
Year: 2004
Chassis: International
Engine: T444e w/ 2000 Allison Trans
Rated Cap: 35
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Pictures help.... probably 2 were never installed. again, pictures speak a great deal
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05-22-2019, 08:11 PM
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#3
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Bus Crazy
Join Date: May 2016
Location: Georgia
Posts: 2,264
Year: 2001
Coachwork: Blue Bird
Chassis: IH
Engine: T444E
Rated Cap: 14
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Quote:
Originally Posted by pratokko
Hi. There are 5 buttons on my steering wheel: doors off/on, flashers, red, horn. However, there are only 3 wires leading away from the steering wheel. Could anyone explain? Thanks
IC CE300 2005
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Either that, or more likely, there's a small circuit board in the wheel, 2 wires are power/ground and the last one is "signal"; a small decoder somewhere receives the "signal" and activates the appropriate thing.
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05-23-2019, 01:07 AM
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#4
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Mini-Skoolie
Join Date: Apr 2019
Posts: 20
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Quote:
Originally Posted by Brad_SwiftFur
Either that, or more likely, there's a small circuit board in the wheel, 2 wires are power/ground and the last one is "signal"; a small decoder somewhere receives the "signal" and activates the appropriate thing.
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wow! so you are saying they converted to digital just to save 2 wires?
As far as pictures go, it's not picturesque. There is the horn and 2 2 position toggle switches on the wheel and there is a three wire connector from the wheel (the only connector). thanks
PS: where do the wires go to? It's a shame I cannot track down a wiring diagram
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05-23-2019, 07:17 AM
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#5
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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Quote:
Originally Posted by pratokko
Hi. There are 5 buttons on my steering wheel: doors off/on, flashers, red, horn. However, there are only 3 wires leading away from the steering wheel. Could anyone explain? Thanks
IC CE300 2005
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Here is an example for you. You push the wheel centre for the horn. What does that do to make the horn blow? It completes the power circuit to ground. The power was already supplied by the horn relay, fusing etc. So you hear your horn.
Could be the same for the doors, flashers etc too so just run a jumper from each of the 3 wires to ground and see what happens. You might need the ign on but maybe not, try both ways.
John
__________________
Question everything!
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05-23-2019, 03:21 PM
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#6
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Mini-Skoolie
Join Date: Apr 2019
Posts: 20
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Quote:
Originally Posted by BlackJohn
Here is an example for you. You push the wheel centre for the horn. What does that do to make the horn blow? It completes the power circuit to ground. The power was already supplied by the horn relay, fusing etc. So you hear your horn.
Could be the same for the doors, flashers etc too so just run a jumper from each of the 3 wires to ground and see what happens. You might need the ign on but maybe not, try both ways.
John
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Hi John. I understand that. I did consider the ground circuit. But still - 3 wires is not enough to operate 5 buttons. thanks
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05-23-2019, 03:49 PM
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#7
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Bus Geek
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 23,829
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
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Quote:
Originally Posted by pratokko
Hi John. I understand that. I did consider the ground circuit. But still - 3 wires is not enough to operate 5 buttons. thanks
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are any of the buttons redundant?
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05-23-2019, 04:16 PM
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#8
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Bus Geek
Join Date: May 2014
Location: West Ohio
Posts: 3,828
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Quote:
Originally Posted by pratokko
Hi John. I understand that. I did consider the ground circuit. But still - 3 wires is not enough to operate 5 buttons. thanks
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Sure it is.
I don't have a wiring diagram in front of me.
But if I had to guess, they add different resistors to the switches, and operate in a similar fashion to that of your cruise control switches on your car steering wheel operate by. Each button has a different resistance, which has a different voltage drop sensed by a logic controller.
4 of the 5 buttons operate like this on one wire. 1 wire operates the horn, and 1 is ground.
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05-23-2019, 07:37 PM
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#9
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Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 19,831
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
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Quote:
Originally Posted by Booyah45828
Sure it is.
I don't have a wiring diagram in front of me.
But if I had to guess, they add different resistors to the switches, and operate in a similar fashion to that of your cruise control switches on your car steering wheel operate by. Each button has a different resistance, which has a different voltage drop sensed by a logic controller.
4 of the 5 buttons operate like this on one wire. 1 wire operates the horn, and 1 is ground.
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THIS!
different resistances... 3 wires.. so likely you have a controlled signal voltage wire... or VCC as its called at +5 volts... then you have a signal ground wire.. (comes from the ECM for a good reference).. and a signal return wire..
when you press a button a resistance is applied to that 5 volts and thus lowers it.. and returns the lowered voltasge back to the computer.. the computer sees the lowered voltage and knows by the value which button you pressed.. pressing 2 at the same time often results in none being acted on. the resistances are purposely set up so that pressing 2 or more buttons at once will not add up to a non programmed function or something erroneous...
-Christopher
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05-24-2019, 12:06 AM
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#10
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Mini-Skoolie
Join Date: Apr 2019
Posts: 20
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Quote:
Originally Posted by cadillackid
THIS!
different resistances... 3 wires.. so likely you have a controlled signal voltage wire... or VCC as its called at +5 volts... then you have a signal ground wire.. (comes from the ECM for a good reference).. and a signal return wire..
when you press a button a resistance is applied to that 5 volts and thus lowers it.. and returns the lowered voltasge back to the computer.. the computer sees the lowered voltage and knows by the value which button you pressed.. pressing 2 at the same time often results in none being acted on. the resistances are purposely set up so that pressing 2 or more buttons at once will not add up to a non programmed function or something erroneous...
-Christopher
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Hi. Are you guessing or do you know that this is how it works? I am familiar in electronics how this can all work I just couldn't believe that IC would go out of their way using the computer to measure voltages to route a switch just to save on wires. That seems crazy since we are talking about simple one pole push button switches (again: horn, door open/close, flashers).
If people who responded are guessing that this is what happens in my bus, how can I find out for sure? No use trouble shooting unless I know exactly what's going on. Thanks
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05-24-2019, 12:14 AM
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#11
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Quote:
Originally Posted by pratokko
Hi. Are you guessing or do you know that this is how it works? I am familiar in electronics how this can all work I just couldn't believe that IC would go out of their way using the computer to measure voltages to route a switch just to save on wires. That seems crazy since we are talking about simple one pole push button switches (again: horn, door open/close, flashers).
If people who responded are guessing that this is what happens in my bus, how can I find out for sure? No use trouble shooting unless I know exactly what's going on. Thanks
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05-24-2019, 06:34 AM
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#12
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Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 19,831
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
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Whether it’s done in your specific bus I don’t know.. I’d have to rexcheck my navistar wiring diagrams.. but it’s stabdard practice in the automobile world with steering wheel buttons , multi function stalks etc..
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05-24-2019, 02:12 PM
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#13
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Bus Geek
Join Date: May 2014
Location: West Ohio
Posts: 3,828
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As chris pointed out, this is a pretty standard way of doing it, it's been done this way for decades.
I don't have the manuals on my desk, and we're pretty busy right now so I don't feel like searching it for you.
Tear the thing apart and see for yourself.
But if all the buttons work, and you're for sure there's only 3 wires. There is a 99% chance that that is how it is done.
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