Fun with brakes: A V85 Alert Service Enigma

[DesertPilot]

For the past 2000 miles or so, my beloved but not entirely undemanding E4 V75 TT has been perplexing me with an intermittent problem. Sometimes the Alert Service warning -- a.k.a. We Wouldn't Dream Of Telling You What's Actually Wrong warning -- comes on when I apply the front brakes.  The symptoms are as follows.

1) It doesn't seem to happen when the brakes are cold.

2) There are no ABS warnings.  That's an entirely different warning.  That actually does tell you what's wrong.

3) I've cleaned the calipers, verified they aren't frozen, flushed the brake fluid, and sacrificed photographs of angry hamsters to Spickle, the Intermittent Failure God.

4) The brakes seem to work fine.

5) Gas mileage seems unchanged, with no sign the brakes could be dragging.

6) After the brakes have gotten hot during a long ride downhill, the Alert Service light may comes on when you apply the front brakes. The light stays on until you reset it by switching off the ignition.

7) After the brakes are hit and the problem has appeared, the bike doesn't have to be moving. It you switch the ignition back on, start the bike at idle, the bike idles with the Alert Service light off, but if you then apply the front brakes with the bike sitting still, the light may come on again.

8) The problem seems to go away after the brakes have cooled off during the freeway ride back home.

I'm going to pull the calipers off one more time to have a look, but I'm running out of ideas here...

[Vagrant]

Do an ABS, T/C reset first. Use the cruise control to hold it at 20-19 MPH.

[DesertPilot]

Thanks for the suggestion.  I did try resetting the ABS/TC calibration once, but I'll give it another go not that I've... sigh... just finished cleaning and inspecting the calipers and flushing the brake fluid again.  I can't find a single thing wrong with the parts of the brake system I can reach.  I hope there isn't some problem with the ABS module...

[aklawok]

 Not being familiar with that system, could this simply be a brake light/switch fault?

[DesertPilot]

Someone on the Advrider forum suggested the brake light switch as well.  This can't be the warning I gather the E5 bikes might display if the brake light is one more than 30 seconds because I can get it to appear the first time I apply the brakes immediately after starting the engine, but I will poke around to verify that the switch is working.

My understanding is that the brake light switch may be a pressure sensor rather than a microswitch, which would mean that if I pull it, I'll have to bleed the brake system... again.  Does anyone here know if this is correct?

[Vagrant]

Any chance you are overfilling the reservoir? It does sound like the switch to me.

[Tom H]

If you need to change a pressure type switch. If your careful when you remove the switch and then apply just a little pressure on the brake pedal or lever to make leak at the fitting when installing, you should be good. I have done this in the past.

Tom

[DesertPilot]

Any chance you are overfilling the reservoir? It does sound like the switch to me.

The shop had filled the reservoir fairly high, close to the top, when they flushed the brake fluid.  I dropped the level slightly, to halfway between the top of the sight glass and the top, when I cleaned and inspected the calipers and flushed the system... again... yesterday.  I'm going to spritz the brake switch with contact cleaner because hey, who knows, then take the bike out for another test ride.

If you need to change a pressure type switch. If your careful when you remove the switch and then apply just a little pressure on the brake pedal or lever to make leak at the fitting when installing, you should be good. I have done this in the past.

Tom

Thanks for the tip!  I'm currently on the fence about ordering a new switch ($59 from AF1?) and going into Throw Parts At The Problem mode.  Since I'd have to figure out where that plug is buried anyway, first step might just be to unplug the current one, dig out my multimeter ("Heigh ho!  Heigh ho!  It's off to work we go!" etc.) , and see just what it's doing.

UPDATE: Careful (or so I claim) inspection has revealed that the switch on the E4 models is a simple  (and $59?) 3-wire microswitch mounted underneath the master cylinder to maximize the chance the mounting screws will fall to the floor, bounce, and roll into the Dimension Of Lost Small Parts if your remove it.  This inspection has also revealed that the brake light seems to be working normally.

[Kiwi_Roy]

I added an LED to the brake light on my V7III
https://www.thisoldtractor.com/guzzi007/schematics/2019_V7_III_E4_Anniversary_-_Racer_-_Special.gif
The brake switches (12) & (13) the green/yellow wire is the switched wire
I picked up the switched wire at the front brake lever with a resistor to LED and LED to the bars (chassis)
the LED lights up if front or rear brake are applied.
Note: the bars were not grounded to chassis rubber mounted I guess but I found a pair of bolts under the triple tree which I jumped together.

Roy

[DesertPilot]

A short donut run to test the results of yesterday's caliper cleaning, fluid flushing, and other Obsessive-Compulsive behavior suggests that as long as the brakes are only in the 'warm to the touch' range, everything is fine.  Unfortunately, they didn't have the donut flavor I was looking for.  I'll have to do a longer ride on steeper roads to see what happens when the brakes get hotter and/or get the right donuts.

[Vagrant]

If the heat does make it act up, you have too much liquid in the reservoir. Have them level, and with the rubber and cap in place, have an air bubble being seen. The fluid needs expansion room.