Gear Indicator Troubleshooting

[The1970's]

Whats the procedure for testing the gear indicator? I found a used switch on ebay for $4 and decided it was time to fix my indicator. After some initial investigation both switches I have function okay but when I ground each contact I get an 8, 9, and a backwards 6. The neutral light works fine and I have power to all the terminals in the harness. Is there a way to test the display or something else to check?

[chuck hahn]

I would plug it into the harness and put the bike on the center stand. Shift up the gears and see if all 5 indicators work..the gear switch on the side of the tranny near the sprocket is nothing more than a ground for each circuit. As you shift, the pin off the shift drum contacts a different spot on the switch and thus changes which gear number illuminates.

[1978GS750E]

Like Chuck said...Put it thru the gears and see if the LCD indicator changes. If not I've replaced them with a cheepie off of Ebay that I paid $1.98 with free shipping from China. Just have to do a little sanding to get it to fit in the old ones' spot in the cluster and some wiring to the old connector.

[The1970's]

Like Chuck said...Put it thru the gears and see if the LCD indicator changes. If not I've replaced them with a cheepie off of Ebay that I paid $1.98 with free shipping from China. Just have to do a little sanding to get it to fit in the old ones' spot in the cluster and some wiring to the old connector.

I may have worded it poorly in the original post but what I meant was that when on the center stand shifting through the gears results in either a backwards six, an 8 or a 9. The backwards 6 appears for two different gears and the 8 appears for two different gears. The neutral light works and the display shows nothing when in neutral. The results are the same if I ground each contact on the switch with it removed from the case. The previous owner told me it used to work but he once put it in 1st with no clutch on accident and it has not worked since. I was hoping it would be a simple fix but I guess it must be the display itself. I have read your older thread about the display replacement. If it's that cheap I may just go ahead with it.

[chuck hahn]

Well it seems one or two of the segments has burnt out or the wires to them have come undone. PM the guy above and see what he has done when he fixed his.

[Steve]

Does the '78 750 have a segmented display? I just looked at a parts fiche and concluded that it just might, but it sure would be nice to know for sure which bike you are talking about. Most of us don't know whether the other bikes in your garage have gear indicators.

Anyway, it's somewhat obvious that you have some connection problems. Might check the display board for loose or 'cold' solder joints, as well as check the connectors for dirty contacts.

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[chuck hahn]

Im really unfamiliar with how the LCD display switches things up. Electronics is my weak spot on bikes.

[1978GS750E]

Let me know if you decide to go the cheap Chinese indicator route. I should have the wiring diagram that I used when I replaced mine. I'll be glad to send it to you. On my 78 GS750 the gear indicator will be blank when the neutral light is on. A simple test with a continuity tester will tell you if the issue is with the switch on the crankcase. As stated earlier, all that switch does is go to ground when the pin is in a certain gear position. Make sure the contacts are clean and the spring is strong before checking.

[The1970's]

Does the '78 750 have a segmented display? I just looked at a parts fiche and concluded that it just might, but it sure would be nice to know for sure which bike you are talking about. Most of us don't know whether the other bikes in your garage have gear indicators.

I should have mentioned it, I am referring to the 78 GS750 and it does in fact have a segmented display. Its a little too cold to ride here in Florida so I'll pull it out tomorrow and check the connections. Otherwise I'll attempt the display swap

[Steve]

I was just a bit surprised that an early ('78) indicator had a segmented display. Most of the bikes that I have seen have been '80-'83, and in the 550-1100 range. For the most part, they have individual lights for the gears, not a single, segmented display.

A general rule when working with electrical stuff: if you are seeing some REALLY strange stuff, check your ground(s). In the case of your indicator, the display is fed power to a common point, then has several ground wires that go down to the selector switch. Each of those wires is connected to a decoder device at the display, that is what tells which segments to light when that wire is grounded. The connections of that decoder to the circuit board is what I suspect.

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