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I've posted on this previously but today after visiting my mate and looking at his LT I have a little more information. Hoping for some advice/opinions. The bike is fitted with a lead acid battery, not a Gel type of AGM. To me this is incorrect as the alternator won't charge it to 14.2 volts, which is what lead acid batteries need in order to be fully charged. I checked his alternator charging voltage at 3000 engine RPM and got 13.6, same as my '05. This tells me he should have either a Gel or and AGM battery. These batteries have different discharge characteristics then lead acid, so I'm tipping this is part of his problem. Now, the real problem - with the engine running I can hear a whine under the seat as if 1 brake servo is running continuously. Pressing the rear brake pedal causes a distinct sevo sound above the other one, to be heard. That all sounds fine. Pulling in the front brake lever I hear nothing different other than the continuously running servo (if that's what it is). The outer red brake warning light (far left) on the dash is flashing rapidly (4 Hz ?), the inner red light is glowing steadily. This is all with the bike sitting in the workshop and engine running. Too wet to test ride today unfortunately. Apart from the battery issue, which he is adament that it isn't a problem, I'm keen to hear what others think about the brake system problem. A dealer has previously told him he needs a new brake control module.
 

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A fully charged 12 volt battery should be 13.2 volts but that would only be when new so the 13.6 should be OK - does not mean his battery is OK - every alternator I have had car/bike has put out 14.5 volts but being in a cold climate area they might run a different regulator than in the south - my diesel VW's all had a dif reg than the gas models

my 2000 probably not as particular as later years with power brakes, is it possible with the servo load running all the time the volts will not reach 14.5
 

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K100Dennis said:
I've posted on this previously but today after visiting my mate and looking at his LT I have a little more information. Hoping for some advice/opinions. The bike is fitted with a lead acid battery, not a Gel type of AGM. To me this is incorrect as the alternator won't charge it to 14.2 volts, which is what lead acid batteries need in order to be fully charged. I checked his alternator charging voltage at 3000 engine RPM and got 13.6, same as my '05. This tells me he should have either a Gel or and AGM battery. These batteries have different discharge characteristics then lead acid, so I'm tipping this is part of his problem. Now, the real problem - with the engine running I can hear a whine under the seat as if 1 brake servo is running continuously. Pressing the rear brake pedal causes a distinct sevo sound above the other one, to be heard. That all sounds fine. Pulling in the front brake lever I hear nothing different other than the continuously running servo (if that's what it is). The outer red brake warning light (far left) on the dash is flashing rapidly (4 Hz ?), the inner red light is glowing steadily. This is all with the bike sitting in the workshop and engine running. Too wet to test ride today unfortunately. Apart from the battery issue, which he is adament that it isn't a problem, I'm keen to hear what others think about the brake system problem. A dealer has previously told him he needs a new brake control module.
You need to brush up on your battery technology. Both Gel and AGM are lead acid batteries with the same charging voltages as flooded cell style LA batteries. The only real difference is that gel style batteries can't be charged as fast as the other types.

http://www.windsun.com/Batteries/Battery_FAQ.htm

I am not sure about your brake problem. Have you checked the fluid levels? Low fluid can cause fault lights. Also, do you know when the fluid was last flushed? If more than two years ago, that should be on your "to do" list pretty soon.
 

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2005 K1200LT
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On the brake issue. Steady on general and 4hz flash on brake fail indicates only residual brake function on one system (sounds like the front). The servos are triggered either but a closed (Stuck) brake light switch or pressure on the brake control circuit. May just have a stuck brake switch that is preventing it from completing the initial self test (That also runs a 4Hz flash until completed) . You can mimic this by holding a brake on your bike when you turn on the key - if you never relase the brake she will stay in the self test mode forever. Try pushing out on the front brake lever and see if that doesn't do the trick.
 

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Discussion Starter #5
Thanks John, I just called my mate and asked him to check if the front brake lever switch can be heard clicking when the lever is pulled in - he confirmed there is no click. I suspect the switch is stuck closed as you suggest. His brake light is not on all the time though, and the light works fine from the brake pedal, so I'm assuming that the light is activated by pressure, or the brake light only works after each circuit has self tested and is happy (which the front circuit is not). His battery (lead acid type) is not good, 1 cell can be seen to be sulphated and it will not charge above 10.8 volts on a standard charger, so he will be replacing the battery this week. I asked him to ckeck the exact type recommended, I'm reasonably sure it should not have a standard lead acid type battery in that '03 model. I'll get the bike to my place when the battery is good and sort through the front brake switch issue, hopefully with a good result. He has also not had the brake system flushed in 5 years, so I'll do that too. And you are correct, holding on the brake lever whilst turning on the ignition mimics that exact fault on my '05. Thanks very much for the info, much appreciated. Dennis
 
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