5 steering wheel buttons but only 3 wires out?

[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

[Rovobay]

Pictures help.... probably 2 were never installed. again, pictures speak a great deal

[Brad_SwiftFur]

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

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.

[pratokko]

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.

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

[BlackJohn]

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

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

[pratokko]

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

Hi John. I understand that. I did consider the ground circuit. But still - 3 wires is not enough to operate 5 buttons. thanks

[EastCoastCB]

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

are any of the buttons redundant?

[Booyah45828]

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

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.

[cadillackid]

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.

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

[pratokko]

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

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

[o1marc]

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

[cadillackid]

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..

[Booyah45828]

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.