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Discussion Starter #1
Anyone have the part # for the rear brake switch on a 2005 LT? I've got the triangle lit up and am 99% sure that it is not the rear lamps. Can't find the switch on the BMW parts fiche.
Thanks to all.
 

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61 31 2 305 855 MICRO SWITCH, PILOT CURRENT, FOOT BRAKE 0.05 1 $67.54 But I would check the adjustment of it first. As you push the pedal you should see the progression shown below. (ignore the selfie) The click should be heard by picture #2.
 

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Discussion Starter #3
John, you are the best, thank you. FYI, all taillights were working so I ordered 2 new anyway and swapped two of the existing while I am waiting to see if it would solve the Red steady on triangle issue. It would come on after about 2-3 miles. Well, I took it for a ride and did not use the rear brake for about 10 miles, no triangle. Applied rear brake and within a mile it was all lit up again. That is why I think it is the switch. I cannot hear any "click" when pushing down on the rear pedal, only the servo whine. The brakes seem fine but I am going to take it apart again. Just installed all Speigler lines, pads all fluids (brake, transmission, rear end, radiator, oil and air/oil/fuel filters) bled all calipers as well as ABS pump. I noticed that the tab on the switch does not disengage the pedal until it is depressed almost fully.
 

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John, you are the best, thank you. FYI, all taillights were working so I ordered 2 new anyway and swapped two of the existing while I am waiting to see if it would solve the Red steady on triangle issue. It would come on after about 2-3 miles. Well, I took it for a ride and did not use the rear brake for about 10 miles, no triangle. Applied rear brake and within a mile it was all lit up again. That is why I think it is the switch. I cannot hear any "click" when pushing down on the rear pedal, only the servo whine. The brakes seem fine but I am going to take it apart again. Just installed all Speigler lines, pads all fluids (brake, transmission, rear end, radiator, oil and air/oil/fuel filters) bled all calipers as well as ABS pump. I noticed that the tab on the switch does not disengage the pedal until it is depressed almost fully.
On all iABS models (integragred ABS with servos), if the brake switch does not work (no change of state, no click), then you will see exactly the symptoms you have described:
- No brake lights on either PEDAL / LEVER activation,
- The "General Warning / Triangle" will show up steady ONLY on brake activation (and will stay ON thereafter until next ignition switch cycle)

Before you buy a new switch, you can test this one with a multimeter (OHMS function) for continuity. On iABS models, you should have continuity when pedal is at rest (brake lights OFF) and no-continuity (open circuit) when the switch is activated. You will need to use very small needles on the Female side of the connector to get a contact inside. See attached photo for location of connector...

The earlier ABS2 models (K1200LT 1999-2001 in USA), have brake switches that are opposite and more common logic (no continuity when pedal is at rest).


ON THE OTHER HAND, if the defect is the rear bulb (or bulb circuitry), the "General Warning / triangle" will show immediately when ignition is turned ON.
 

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Discussion Starter #5
Thanks to both John and John, I appreciate the feedback. I just checked the bike in the garage and without the triangle lit up (usually takes 3-4 miles and use of the back brake) I have both top and bottom brake lights from both pedal and lever activation. I will check it again later when I take it out and the triangle lights back up to see if I still have brake lights at that stage.
 

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Thanks to both John and John, I appreciate the feedback. I just checked the bike in the garage and without the triangle lit up (usually takes 3-4 miles and use of the back brake) I have both top and bottom brake lights from both pedal and lever activation. I will check it again later when I take it out and the triangle lights back up to see if I still have brake lights at that stage.
If it appear to be intermittent and the switch mechanical test (or OHMS test) is not conclusive 100%, then you may request a GS911 readout assistance from a forum member in your area.

In case such as this (any / both of the 2 warnings - ABS or General warning), the system will keep all faults in memory until either:
1) A fault reset is done (using dealer's computer or a GS911)
2) the battery is disconnected for a fairly long period

Normally, for a case with symptoms like yours, the ABS fault in memory will be:
17917: Defective REAR brake switch

I am curious to see if it is another code.... ??

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P.S.:
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I have also seen one case where the owner had pulled the large iABS modulator connector during a bleeding procedure. The large connector had been pushed back a bit crooked and one of the pins (related to brake switch signal) had been bent. Final result was the same as having a brake switch that emitted no click (no signal). The small pins are on the modulator side of the connector.
 

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Just be aware, just because you can hear a switch make a clicking noise does not mean that the internal contacts are always making and breaking correctly. The internal mechanism can get a bit tired after time and it could be an intermittent fault. If in doubt replace it.
 

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Discussion Starter #8
Hey John, this is Jay. I appreciate all the help you have been offering. Unfortunately I am no electrician (just a wrencher). I have an inexpensive multimeter and set it on 200 ohms, Red connector to VohmmA and black lead to com. With pedal at rest I'm reading around 1.5-2 ohms. However with the pedal depressed it is the same. Bad switch?
 

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Hey John, this is Jay. I appreciate all the help you have been offering. Unfortunately I am no electrician (just a wrencher). I have an inexpensive multimeter and set it on 200 ohms, Red connector to VohmmA and black lead to com. With pedal at rest I'm reading around 1.5-2 ohms. However with the pedal depressed it is the same. Bad switch?
If you are just trying to read circuit through the switch it doesn't matter which lead of the multimeter you put on which side of the switch. But if you are across the switch and getting those readings then yes your switch could be bad. Important test for your meter though is before you test the switch test your meter. Put the leads together and make sure you get close to 0 ohms.
I once spent 2 hours diagnosing a problem on a machine and found that my meter leads were broken.
 

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Discussion Starter #10 (Edited)
Leads together, comes right down to 0 or .1, I'm testing leads at the female side of the switch plug with meter set at lowest ohm setting (200) BTW: I removed the switch now completely and with the bike powered up when depressed manually the brake lights come on as they should and the servos engage. I can also hear the switch "click". When released lights go out and servos disengage. It appears to me that the switch is fine but I do not know why the triangle comes on after a couple of miles when the rear brake is depressed. Everything seems ok.
 

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Leads together, comes right down to 0 or .1, I'm testing leads at the female side of the switch plug with meter set at lowest ohm setting (200) BTW: I removed the switch now completely and with the bike powered up when depressed manually the brake lights come on as they should and the servos engage. I can also hear the switch "click". When released lights go out and servos disengage. It appears to me that the switch is fine but I do not know why the triangle comes on after a couple of miles when the rear brake is depressed. Everything seems ok.
See attached photo...
You need to insert delicately 2 small needle at FeMale connector side as shown by red arrow. If needle is too big, you will feel too much friction when inserting AND you will damage the internal of the connector. After this, it will not be usable to function OK on Male harness side (too loose.... no jokes please...).

If switch is OK and needles are right sizes, you will read 0 or 0.1 OHMS value like when you touch 2 Multimeter wire together.

ONLY when switch is activated (pedal depressed) should your multi-meter read "infinity" or whatever value it shows when the 2 wires are apart.


P.S.: By design, on iABS servos models, the modulator internal pressure sensors will sense that you have created hydraulic pressure on pedal application, thus it can activate the servos / brakes and the brake-light EVEN IF THE SWITCH IS DEFECTIVE. The General-Warning (triangle) and the resulting fault code is there to warn you that something is not working as it should.

HOWEVER, in addition to above, it also checks for brake switch continuity when the ignition is turned ON (initial self-check). Hence, you should NOT have any servo power if the switch is completely disconnected (not what you said above if I understand your post). In such case, switch disconnected, you should get a fast-flash of the ABS warning after ignition ON cycle. Removing the switch AFTER the ignition ON cycle will change the behavior temporarly.... until next ignition OFF-ON cycle.

This logic and behavior is one part of the internal diagnostic and fault tracking of iABS: on these modulator, it is expected the switch will ALWAYS activate early - before a certain pressure level is reached - otherwise a fault is shown and logged in memory.
 

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Discussion Starter #12 (Edited)
Thanks. Removed brake switch from side plate and disconnected junction, thus removing switch from bike. Attached sewing needles to test leads and set multimeter at 200k ohms. With Leads not touching anything and meter on, it reads infinity. With meter still on and touching leads together the meter reads zero. NOW.... with sewing needles inserted into female connector end of switch and the switch disengaged (at rest) the meter reads infinity. With needles still connected and meter on, when the switch is engaged (depressed) the meter reads zero. Indication of a good switch I hope?
My apologies John. With the switch removed from the pedal the continuity is exactly as you had described. My perception was backward. With the microswitch, when the contact button on the switch itself is depressed the switch is off. Vice versa when the button is released the switch is on. I am definitely not an electrician.
Thanks for all the help. Still have to figure out why the triangle but I feel the bike is safe to ride.
 

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With the switch removed from the pedal the continuity is exactly as you had described. My perception was backward. With the microswitch, when the contact button on the switch itself is depressed the switch is off. Vice versa when the button is released the switch is on. I am definitely not an electrician.
Thanks for all the help. Still have to figure out why the triangle but I feel the bike is safe to ride.
Yes that is correct operation. The switch is depressed (closed) when the pedal is not pushed and opens when the pedal is pushed. Your bike is acting like it "sees" the closed switch all the time. This could be caused by a shorted wire between the switch and the ABS connector.

Since the switch is correct, re-install it and then check it again for zero with the pedal normal and open when the pedal is depressed. If that is good then check again for the same condition as John had shown on the ABS connector but it looks like you already did that here:
Hey John, this is Jay. I appreciate all the help you have been offering. Unfortunately I am no electrician (just a wrencher). I have an inexpensive multimeter and set it on 200 ohms, Red connector to VohmmA and black lead to com. With pedal at rest I'm reading around 1.5-2 ohms. However with the pedal depressed it is the same. Bad switch?
If that was your measurement at the ABS connector (and confirmed again ) then there is a short somewhere in the harness. I would start at the lower connector on the bike side and start unwrapping the cover looking for crushed wires.
 

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Discussion Starter #14
Thanks to all, especially jzeiler and sailor (John & John) for all the help. Problem solved!! Removed switch from bike and tested OK, sprayed with contact cleaner (ran into fresh tar & chip on way to Sturgis) and reinstalled after relocating switch junction and using fewer tie wraps to relieve stress on all harnesses. Bingo, no light.
Now if I could just make up my mind about tires, hmmm lol.
 
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