Flashing Tail Light / No fuel gauge

When all the smoke has escaped from inside the wires...
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Stu
Posts: 123
Joined: 04 Sep 2017, 10:12

Flashing Tail Light / No fuel gauge

Post by Stu »

I'm trying to put my 750 back together finally, but have a couple of minor electrical issues that aren't showstoppers but are wicking me off.

First, my indicators are dimming my back light... you know what I mean, indicator lights flash on, tail light gets dimmer, indicators go off, tail light gets brighter. I've always understood this to be a bad earth somewhere... but I can't find it. I've cleaned up all the earth connections, and all the connectors I can find, but no improvement at all. It's probably not bad enough to fail an MoT, but annoying nonetheless. Any ideas? Could it be in the flasher unit itself?

Secondly, my fuel gauge doesn't work. Didn't work when I got the bike four years ago. I've just tested the sender in the tank, and it's doing exactly what it is supposed to; 10 ohms to 100 ohms. It appears from the wiring diagram that the sender is just a resistance to earth, but I'm getting no voltage on the yellow/white wire at the sender. Again, I can live without a fuel gauge, but it's there and should work! Any thoughts? Anyone fixed this?

Thanks!
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Stu
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Joined: 04 Sep 2017, 10:12

Re: Flashing Tail Light / No fuel gauge

Post by Stu »

So, to answer my own question (‘cus clearly no other bugger is as interested as I am ;) ) I’ve been digging into the wiring diagram.

The only thing that can cause the tail light issue that I can see is a floating earth at the back end. I’ll get the meter out tonight and try and trace it through to the earths at battery and frame and see what’s going on and where the resistance is. Interestingly, most bikes I’ve had this kind of issue with earth everything back through the frame, but the Z doesn’t, having black and yellow earth return wires everywhere.

Because of this, and separate fat earth return from the motor to the battery, I haven’t worried too much about ensuring a solid electrical contact between the motor and frame. This is often an issue with newly powder-coated frames. The black and yellow wires are connected separately to frame and to battery negative, but something’s floating somewhere. Again, meter out tonight. I might whip out the rear top engine bolt and grind some paint off the back of the little triangular bracket to tie the motor and frame solidly together.

With the fuel gauge, looks like only two things could be wrong. The tacho is working, so power is getting to the gauge (or at least very close to it). Power is not getting to the sender, so either the gauge is open circuit somewhere inside the tacho or the connector/wire back to sender is damaged. Guess what… meter out tonight!
Swampy
Posts: 323
Joined: 04 Sep 2017, 18:01

Re: Flashing Tail Light / No fuel gauge

Post by Swampy »

I'm not very good on electrics tbh but I did think it was an earth problem, so I cant really comment on something that I don't know, but keep us updated please ;)
Swamps :)
Freddy
Posts: 695
Joined: 06 Sep 2017, 11:06
Location: Sydney Australia

Re: Flashing Tail Light / No fuel gauge

Post by Freddy »

Stu wrote:I'm trying to put my 750 back together finally, but have a couple of minor electrical issues that aren't showstoppers but are wicking me off.

First, my indicators are dimming my back light... you know what I mean, indicator lights flash on, tail light gets dimmer, indicators go off, tail light gets brighter. I've always understood this to be a bad earth somewhere... but I can't find it. I've cleaned up all the earth connections, and all the connectors I can find, but no improvement at all. It's probably not bad enough to fail an MoT, but annoying nonetheless. Any ideas? Could it be in the flasher unit itself?

Secondly, my fuel gauge doesn't work. Didn't work when I got the bike four years ago. I've just tested the sender in the tank, and it's doing exactly what it is supposed to; 10 ohms to 100 ohms. It appears from the wiring diagram that the sender is just a resistance to earth, but I'm getting no voltage on the yellow/white wire at the sender. Again, I can live without a fuel gauge, but it's there and should work! Any thoughts? Anyone fixed this?

Thanks!
Run a temporary earth wire from the tail light bulb holder (a small clamp of some sort to hold it in place) back to the negative side of the battery terminal. Now you really have eliminated all earth points. See what happens then.

Fuel gauge not working, what's the three most likely points of failure? Fuse, fuel gauge, fuel sender. Disconnect the plug under the rear of the right hand side of the fuel tank and jump the two terminals with an LED test light, ignition on. If the fuse and gauge are good I'd expect either the light to illuminate and/or the fuel gauge to move. Also check you have power in one wire with the LED test light earthed to the battery.
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Stu
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Joined: 04 Sep 2017, 10:12

Re: Flashing Tail Light / No fuel gauge

Post by Stu »

Thanks, Guys. Yes, Freddy, my thoughts have been running on similar lines.

Popped out to the garage for 5 minutes to fiddle last night and the right indicator mysteriously stops flashing... front hard on, rear off. Opened the offending unit and... :shock: ... absolutely full of rust and crap. Looks great on the outside so I'd just bolted them back on! The left one's no better, can't get either bulb out, so I've ordered two new ones. Will try again once all the corrosion is out of the circuit. The front ones are much better, so they will stay for now.

Will try your suggestion with the fuel gauge but as far as I can measure, there's no power at the plug at all. Suggests power not getting to/from the gauge itself. Same positive wire is powering the tacho, which is working fine, so I strongly suspect the gauge itself or the wiring back to the plug under tank. Will have a better look next time I have the headlight open.
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Ivor
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Location: Hampshire UK overlooking the Needles :)

Re: Flashing Tail Light / No fuel gauge

Post by Ivor »

cheers for the info , mines been sat around for a few year s so i'll whip the indicator covers off and check what they look like inside before they get too bad to repair
1995 ZR1100A2
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Stu
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Re: Flashing Tail Light / No fuel gauge

Post by Stu »

So, having replaced both rear indicator assemblies... no difference whatsoever!

Stripped a long piece of heavy wire and used it to jump the earth from the flashing rear indicator all the way back to the battery negative... still no difference whatsoever! With earths completely separate, they cannot be interfering with each other, so voltage across battery must be dropping with the current draw of the indicators.

I've given up for now, there doesn't seem to be anything wrong with the existing earths from the tail end... maybe it'll be better with the motor running and charging but I haven't checked. Too loud in the garage with that 4 into 1... Will check once the new baffle arrives!

Someone do me a favour? Bike in the shade. Ignition on, engine not running, indicator flashing and lights on... does your tail light dim slightly when the indicator flashes on?
Freddy
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Joined: 06 Sep 2017, 11:06
Location: Sydney Australia

Re: Flashing Tail Light / No fuel gauge

Post by Freddy »

Stu wrote:
Someone do me a favour? Bike in the shade. Ignition on, engine not running, indicator flashing and lights on... does your tail light dim slightly when the indicator flashes on?
Yes, taillight bulbs dims something like 10% (pure guess to indicate amount) at each flash.
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Stu
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Joined: 04 Sep 2017, 10:12

Re: Flashing Tail Light / No fuel gauge

Post by Stu »

Great... then I'll stop trying to fix it :oops:

Thanks, Freddy!
hugojose
Posts: 161
Joined: 05 Sep 2017, 00:43

Re: Flashing Tail Light / No fuel gauge

Post by hugojose »

…..and if you switched to LEDs, the dimming would stop all together,....but don't get into that now. You have other problems. Overcoming the single dash blink indicator is somewhat involved.
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