front brake fluid level sensor?

[6m459]

My red bike has an issue with the f/b fluid level sensor float switch. I seem to have to fill the reservoir too full of fluid to satisfy it.

 

If I put in what it seems to want, it over flows when I put on the lid. If I put in fluid just to the level indicated on the sight glass, it doesn't satisfy the level switch and I get the red flashing CMS etc.

 

Is this common?

 

Thanks,

 

Brian H

[Rocket]

My red bike has an issue with the f/b fluid level sensor float switch. I seem to have to fill the reservoir too full of fluid to satisfy it.

 

If I put in what it seems to want, it over flows when I put on the lid. If I put in fluid just to the level indicated on the sight glass, it doesn't satisfy the level switch and I get the red flashing CMS etc.

 

Is this common?

 

Thanks,

 

Brian H

 

No it's not common at all. Are you doing this, with the unit as level as possible (not tilted)

 

I would test the switch with a multimeter at the connector (somewhere behind the headlight), with the float in the upper position & lower position. You should have continuity in the upper position & no continuity in the lower position.

 

It is also possible of dirty / corroded contacts at the connector, or damaged wires for the switch. The final but unlikely (in this case) is a CMS solder joint problem.

[6m459]

No it's not common at all. Are you doing this, with the unit as level as possible (not tilted)

 

I would test the switch with a multimeter at the connector (somewhere behind the headlight), with the float in the upper position & lower position. You should have continuity in the upper position & no continuity in the lower position.

 

It is also possible of dirty / corroded contacts at the connector, or damaged wires for the switch. The final but unlikely (in this case) is a CMS solder joint problem.

 

Sorry, I should have said. The bike is level, its on its centre stand in my garage (the floor has a couple of degrees tilt towards the door, to aft as the bike sits, to shed water but is essentially dead level). Handle bars oriented straight ahead.

 

I narrowed the cause of the CMS alert down to the front fluid level switch by using a multi meter at the connections behind the headlight. By watching the meter, I can see exactly when the float switch triggers. It behaves as you suggest but not at the right level nor particularly consistently at any level it seems.

 

I have alternately filled the reservoir to both the level indicated on the sight glass and to the level that satisfies the switch and have used a pointy tool to gently sink the switch float and then let it bob up again. The float itself appears to be sufficiently bouyant, yet it looks to me like the float switch is very insensitive and does not trigger at the correct point at all, nor particularly consistently at any level.

 

I have had my CMS out, this past week, and have resoldered all connections and joints. None looked suspect before hand (and I have made my living doing electronic production Q/C work in the past so I know a bad solder joint when I see one) but I reflowed them all to be sure.

 

If I put a jumper across the wires, behind the head light, that the front fluid level switch should plug into, then the CMS is happy.

 

After sleeping on this overnight, I am wondering if the magnet in the float, that causes the switch to trigger, has lost its potency? If I recall correctly there is a ciirclip that looks as if, once removed I could lift the float out of the reservoir. I am thinking of trying other magnets in there some how. Anyone got a spare float?

 

BTW, I seem to also have a similar situation with my engine oil level sensor switch but I have yet to investigate that as fully.

 

Thanks,

 

Brian H.

[Rocket]

I have alternately filled the reservoir to both the level indicated on the sight glass and to the level that satisfies the switch and have used a pointy tool to gently sink the switch float and then let it bob up again. The float itself appears to be sufficiently bouyant, yet it looks to me like the float switch is very insensitive and does not trigger at the correct point at all, nor particularly consistently at any level.

 

If I put a jumper across the wires, behind the head light, that the front fluid level switch should plug into, then the CMS is happy.

 

Thanks,

 

Brian H.

 

The fluid level mark at the sight glass is the lower level, the full level line is on the inside. If the sight glass is easily seen through, you can bypass the sensor by cutting the wires & connecting together, to stop the CMS error. Or put a new sensor assy in (currently listing for $45. @ flatout MC + shipping), CDN dealers will be higher but no shipping fees.

 

How you want to handle this issue is up to you, but these are my suggestions.

 

BTW to open mine, the scoot is on the side stand, with the front wheel turned, so the cover is as level as possible. This depends on the riders preferred positioning of the levers, when riding.

[lonestarmedic]

You mentioned the engine oil sensor also being a bit inaccurate. With 2 sensors amiss, could it be a grounding problem at the CMS? I can't remember the circuits. I just know if I am chasing a problem like this I will check my grounds and even run an extra temporary ground. I doubt that the magnet is a problem. If it is a magnet driven sensor, then I would suspect the hall effect sensor. Good luck on this one.

 

JB

[6m459]

You mentioned the engine oil sensor also being a bit inaccurate. With 2 sensors amiss, could it be a grounding problem at the CMS? I can't remember the circuits. I just know if I am chasing a problem like this I will check my grounds and even run an extra temporary ground. I doubt that the magnet is a problem. If it is a magnet driven sensor, then I would suspect the hall effect sensor. Good luck on this one.

 

JB

 

Thanks, but in both cases, the CMS always reads properly when I remove a sensor from the circuit and simulate its function with a jumper lead. Also when I test the sensors with my multimeter, their behaviour is equally erratic. I think this demonstrates pretty clearly that the problem is with the sensors themselves.

 

Also, I doubt it is a hall effect sensor. My bet is that its a reed switch & a floating magnet.

 

Brian H.

[6m459]

The fluid level mark at the sight glass is the lower level, the full level line is on the inside.

 

I have not seen a full level mark on the inside, where do I look? Why put a full line on the inside when you have a sight glass?

 

I have always inferred the word "lower" on the sight glass to mean 'don't fill beyond this point' presumeably because the reservoir isn't always level and if filled beyond this point some may slosh out the vent when leaning on the side stand or tipped for any other reason.

 

Am I out to lunch here?

 

Thanks,

 

Brian H.

[Neil86]

I have always inferred the word "lower" on the sight glass to mean 'don't fill beyond this point' presumeably because the reservoir isn't always level and if filled beyond this point some may slosh out the vent when leaning on the side stand or tipped for any other reason.

 

Brian...the diaphragm seals the fluid from the vent.....the vent allows the diaphragm (and the fluid under it) to be at atmospheric pressure, but not allow the fluid to be exposed to air. Typically the level should be about 1/2~3/4 full in the sight port to allow room for expansion due to heat from brakes.

[Rocket]

I have not seen a full level mark on the inside, where do I look? Why put a full line on the inside when you have a sight glass?

 

I have always inferred the word "lower" on the sight glass to mean 'don't fill beyond this point' presumeably because the reservoir isn't always level and if filled beyond this point some may slosh out the vent when leaning on the side stand or tipped for any other reason.

 

Am I out to lunch here?

 

Thanks,

 

Brian H.

 

The lower is the minimum amount of fluid before topping up, the line on the inside is a long one(opposite side from sight glass if I remember correctly), just below where the diaphram sits. I fill to a little below that line, leaving some room for expansion, but not a lot as the fluid level will drop as the pads wear.

 

So maybe, there is nothing wrong with the level switch, just not enough fluid in there, to shut off the warning.

[6m459]

Thanks one and all for your insights. I have topped up a bit and it seems to be behaving itself. I haven't been having a good day today on various fronts, so I think I'll puzzle over this one again another day.

 

Cheers,

 

Brian H.