K11 Owners Group

ljjohns

I'm working at a distance--the bike (the '93 K11LT with ABS I) is up in Orondo, WA while I'm down here in El Paso.

Symptoms:
"triangle" warning light does not go off after both front and rear brakes are activated.
A new brake light bulb was installed; front brake activates rear brake light; footbrake does not activate brake light.
My friend in Orondo pulled off the footbrake assembly and put a continuity meter on the switch he removed: the switch shows current flowing when the plunger is not depressed; the circuit is broken when the plunger is depressed.

Is it possible that he pulled the "sidestand switch" instead of the brake-light switch?

Larry Johnson
El Paso TX
_________________
1993 K1100LT (Washington)
1995 K1100LTSE
1996 K1100LTSE (parts)
2003 K1200LTC
1991 K75RT

Tim (Midland Section) · Posted: Mon May 23, 2011 4:37 pm Post subject:

That is correct. The pedal in the up position holds the switch in the open circuit state.
IIRC the sidestand switch does operate in the same way. IT has green wires.
HTH
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Regards Tim,

Grey haired riders don't get that way by pure luck
1996 Guzzi Cali3 LAPD
1972 750 Commando
G6HRN
#485

Inge K. · Posted: Mon May 23, 2011 4:53 pm Post subject:

Hi!

You might have the same problem as an other member recently got,
check "Brake light question" a bit further down the page.

Inge K.

ljjohns · Posted: Mon May 23, 2011 4:57 pm Post subject:

Tim: Thanks. That makes sense.

Inge: That's why I started the topic; his issue was with the front brake lever; mine is with the rear. It looks like we need to dig a bit more into the BMU.

Larry Johnson
El Paso TX
_________________
1993 K1100LT (Washington)
1995 K1100LTSE
1996 K1100LTSE (parts)
2003 K1200LTC
1991 K75RT

ljjohns · Posted: Mon May 23, 2011 6:42 pm Post subject:

Still trying to sort this out at a distance.

I'm assuming that the current to the brake light from both the front and the foot brakes passes through the Bulb Monitor Unit.

So is there a relay in the BMU or only a circuit board that measures current flow, etc. to check the circuits?

If it's just a measuring device, then I should probably have my friend check the connections from the BMU to the rear brake light, right? Or is there a separate fuse between the BMU and the brake light (or between the rear brake switch and the BMU) that is separate from the front brake circuitry?

Thanks.

Larry Johnson
El Paso TX
_________________
1993 K1100LT (Washington)
1995 K1100LTSE
1996 K1100LTSE (parts)
2003 K1200LTC
1991 K75RT

Scott_Anderson · Posted: Mon May 23, 2011 10:02 pm Post subject:

Larry, here's a color diagram of the basic wiring to/from the bmu.
Some of it can be translated with google chrome as it's in german.

It doesn't get detailed about the internals of the bmu, I'm still thinking that I have seen something somewhere about the bmu internals.

edit:
Ok, here Drake gives some details about how to bypass the bmu altogether.
http://k11og.org/forum/viewtopic.php?t=8669
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1995 K1100LT 0302044
2017 FLHTK Ultra Limited
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1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

Tim (Midland Section) · Posted: Tue May 24, 2011 4:43 pm Post subject:

Yup, the BMU monitors the current passed in the brake & tail lights. It trips an internal "relay" in the case of brakes & constantly monitors the tail whilst turned on, which is why the "triangle" sometimes flashes when the tail goes intermittant. This current measuring is also why LED's & incorrect rear lamp wattage (should be 10 Watts NOT 5 ) cause BMU to light.
Check earths (grounds) bulb wattage, integrity of connectors & reliability of switches. BMU's do fail, but it is nowhere near as common as ABS controller failure.

The brake current will pass through the BMU even if the sensor bit is faulty.
So if one brake doesn't light the lamp, make it work, before condemning the BMU as faulty.
Microswitches as found on the rear brake, will still click & but not pass enough current. Test with a battery & 21watt lamp to be certain. Mine did just that.
HTH
_________________
Regards Tim,

Grey haired riders don't get that way by pure luck
1996 Guzzi Cali3 LAPD
1972 750 Commando
G6HRN
#485

Flying Duck · Posted: Thu May 26, 2011 9:42 am Post subject:

Larry:

You might want to put this issue on hold. When I go visit the bike in June I'll take some spares of the various components and get it sorted out for you.
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ljjohns · Posted: Thu May 26, 2011 9:51 am Post subject:

Will do. Thanks, Drake.

Larry Johnson
_________________
1993 K1100LT (Washington)
1995 K1100LTSE
1996 K1100LTSE (parts)
2003 K1200LTC
1991 K75RT

Geoff · Posted: Thu May 26, 2011 8:47 pm Post subject:

Sounds like the same problem I had, a bad Bulb Monitoring Relay.

http://k11og.org/forum/viewtopic.php?t=10358
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