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Discussion Starter #1
I got the trike back today (2000LT) from BMW Motorcycles of Fort Worth after a clutch/seal replacement, engine service. Ooops, the radiator fans run from key on continuously! I have checked the connection to the water pump temp sensor, OK. Anyone have any idea what they might have done to make this happen? Fans should not run until water is hot! Their tech is off today and Saturday, cannot ask him.
 

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2011 R1200RT
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If just one fan is continually on I would suspect an incorrect connection.
If both fans are on continuously I would suspect a relay.
Unfortunately it takes a bit of disassembly to get there, so best to wait until your tech gets back.
 

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Wrencher Extraordinaire
2005 K1200LT
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The temp sensor on the back of the cylinder head (near the coil pack) if disconnected will trigger the fans on at key turn. Easy check but you have to pull some body panels.
 

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I got the trike back today (2000LT) from BMW Motorcycles of Fort Worth after a clutch/seal replacement, engine service. Ooops, the radiator fans run from key on continuously! I have checked the connection to the water pump temp sensor, OK. Anyone have any idea what they might have done to make this happen? Fans should not run until water is hot! Their tech is off today and Saturday, cannot ask him.
Could be a bad radiator fan relay (does not fail often), but more probable is a bad Engine-temp-sensor (located into cylinder head of cylinder #4). First, check if connector of this sensor is not plugged correctly or if a wire is damaged, the behavior is the same: fans will run full time when values from sensor are out of limit.
See this post for more details: http://www.bmwlt.com/forums/showthread.php?t=61960

Better if you have a GS911, but you can do a rough check of resistance (ignition OFF) using an OhmMeter. This PICASSA picture tutorial is for the k1200RS, but the K1200LT has the same sensor - only the end connector is a bit lower:
https://plus.google.com/photos/101489741192933663432/albums/5715782307964672065
At 70F (or 21 Celcius), the reading should be close to 2500 Ohms. When engine is hot, you should read 220 (hot) to 170 Ohms (very hot). Leave ignition OFF for these tests.
 

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+1 On JZ's reply, I know from my own experience that when the head temp sensor located on the back of the head goes bad, the fans will kick on prematurely, so I could see that if the shop disconnected the head temp wire, it would kick the fans on immediately.. pretty easy check/fix, just got to pull tupperware on the left side, you can see the head temp sensor sticking out of the rear side of the head, follow the wire, and the connector is just under the section of the tupperware that is under the seat area. Or you could ride it back to the shop, and tell them that they need to fix it...
 

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If the fans kicked on immediately, wouldn't the repair shop (mechanic) notice that before giving you your bike back? They must of been in a hurry to get that bike out!
 

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Discussion Starter #8
Wow, what a great forum!! Great knowledge! We have been on a motor home trip to South Dakota, so was not able to tackle this issue until today.

The sensor is open, infinite resistance. I do not have the tools to remove/replace the sensor, so back to the shop she goes! (I don't know how anyone can get a wrench on that sensor!!!)

I really appreciate all the input from all of you, Thank You very much!!

Blessings. :wave
 

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Discussion Starter #9
Well, I took another look, and I was able to remove the defective sensor. Was not too bad after all!!

Now to find a replacement!!! :)
 

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Discussion Starter #10
Yes, you would think so!!
 

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I got the trike back today (2000LT) from BMW Motorcycles of Fort Worth after a clutch/seal replacement, engine service. Ooops, the radiator fans run from key on continuously! I have checked the connection to the water pump temp sensor, OK. Anyone have any idea what they might have done to make this happen? Fans should not run until water is hot! Their tech is off today and Saturday, cannot ask him.
About LT fans. I have had a continuous problem with a blown fan fuse since I purchased this LT, my 3rd, in July of 2014. The fuse would blow after the fans cycled a couple of times. I was finally able to get to a dealer two weeks ago who diagnosed the problem as a bad fan motor, excessive axial play and high friction in rotation, on the right side. New motor and fan installed, still blows the fuse. Dealer now telling me the other motor is bad as well . The tech exchanged fans, left side, with another bike in the shop and cycled them 6 times with no failure. I think that a failure of both fans, excessive current draw by both, as highly improbable. One caveat, the bike is a 2009 with only 4,992 miles on it when I bought it, and it came from the Midwest. Lots of humidity and too much time sitting.
I searched the forum for this type of failure. Nothing popped up. Any thoughts, similar experience??
 

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2005 K1200LT
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If both are bad then both were subjected to the same environment. Lack of use and high humidity could have driven the corrosion that caused the excessive play. Also the 09s were assembled with the last bits off the assembly line, just say'in.
 

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That is the only thing I could come up with as well. I had another 09, wrecked in April, that was flawless. Thought I could get lucky again, lol.
 

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Discussion Starter #14
OK, the fix is in!! I have followed the recommendations of this forum, and have successfully repaired this LT trike!! First on ordering the replacement sensor....I ordered from a BMW parts firm, didn't hear anything, called 2 times, nothing. So, I ordered another from 2 Wheel Pros. They were superb, received the part in 2 working days as advertised. In order to make sure I would not destroy the new part, I first put a 2.2K resistor on the connector to the fan relay, and sure enough, the fans did not start at key on. I was concerned that something else was wrong downstream from the sensor. I checked the voltage also, about 4.2 volts DC. So, I plugged in the new part, and yep, fans did not start at key on. All put back together now, behaves as it should! I want to thank everyone on this forum who contributed to my success!! :D
 
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