Gen III screen adjustment limits

mcatrophy · Oct 16, 2014

Idly looking at my voltmeter while I was playing with my controls, I moved the screen up to its limit. Low and behold, the voltmeter voltage dropped appreciably when the limit was reached, until I released the adjustment rocker switch.

Ignition on, engine not running: 12.4 volts

Screen moving up: 12.2 volts

Screen at limit: 11.9 volts

Release the switch: 12.3 volts

Checked the best electrical schematic I have (from the Haynes manual). There are no limit switches to stop the current to the motor. It simply stalls.

Yuck.

That's what you get for moaning to Yamaha about having an auto-retract.

Fred W · Oct 16, 2014

I don't recall there ever being any limit switches. If there were, there certainly would have been failures. At least that is my experience with all sorts of micro-limit switches.

While not very elegant, at least it is simple, and will probably result in fewer malfunctions this way.

mcatrophy · Oct 16, 2014

Simple, yes.

To me, as an engineer, it is crude, and likely to cause problems simply because of the high stall current of the motor heating its windings and probably where the brushes contact the commutator.

All it needs is for you to be running your screen down, turned away talking to someone/admiring the view/watching for lightning flashes, you could hold that on for a minute or so without realising. At some stage, smoke will start to come out, and we know it'll stop working without its smoke.

There are limit switches on Gen IIs, and I believe on Gen Is.

In this picture of my (ex) '06, look at the runner to the left of the picture, at the top left you can see the upper limit microswitch.

(Click on image for larger view)

And (looking up at the bottom of the same runner) this shows the lower limit switch, centre of picture

Next time I have my battery cover off, I'll measure the current.

mcatrophy · Oct 17, 2014

So I had my battery cover off, I made some current measurements.

All these measurements were made with the kill switch on, the battery in a good state of charge.

This first set of readings were taken with the bike's voltmeter measuring after my ammeter, so nearer the actual ignition circuit voltage that was across the motor.
(Click on image for larger view)
Ignition only, no screen movement, about 3.9 amps, 11.8 volts.

Screen moving, about 6.3 amps, 11.9 volts; Screen stalled, 15.6 amps, 9.9 volts.

So, screen motor current moving is about 6.3-3.9=2.4 amps;

With screen motor stalled, motor current is about 15.6-3.9=11.7 amps.

Ignition voltage indicated with the motor stalled=9.9 volts.

I then measured with the bike's voltmeter across the battery.

Current when stalled: 15.8 amps, battery voltage=11.9 volts.

At the maximum current, my meter was dropping 11.9-9.9 = 2 volts, so in practice the current would be 20% higher without the engine running. With the engine running there would be nearer 14 volts, so the current would be nearer 14/9.9*11.7=16.5 amps.

The screen current comes from the signalling current fuse which is rated at 10 amps. Also on this fuse are the indicators, brake lights, horns and glove-box solenoid, so any of these may need adding to the current in the fuse (solenoid current always on, 14V, 20 ohms = 0.7 amps).

So, even if you don't mind risking burning out your screen motor, you could easily lose the brake lights and indicators. And, where do you keep your spare fuses? In the glovebox, of course.

My advice: Don't ever hold the switch on with the screen on either of its limits.

art miller · Oct 17, 2014

Thanks guys for this very useful info.

wheatonFJR · Oct 17, 2014

Sounds like another sticker to put on the tank...

SouthernCruizer · Oct 17, 2014

ummm...is it just me, or does this sound like an answer to a question that would never be asked, or a solution to a problem that does not exist??

DaJudge · Oct 17, 2014

SouthernCruizer said:
ummm...is it just me, or does this sound like an answer to a question that would never be asked, or a solution to a problem that does not exist??

I've never heard that having FJR windshield motors burn out or blow fuses has been an issue. Is it? Those on all three of mine worked just fine.

Tis but a glimpse into the mind of an engineer. I get to see this often as my oldest son is one.

Fred W · Oct 17, 2014

No, but from what mcatrophy says, this is a new "feature" of the 3rd gens, so we may start to see it going forward.

Of course that is to be seen, but I will heed his warning and not hold the up or down buttons when already at a limit for too long. Why tempt fate?

Gen III screen adjustment limits

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Gen III screen adjustment limits

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