Cooling fan doesn't start

[dabk75s]

I have a 1988 K75S that is having a problem with the cooling system fan starting. The bike is running great with no other problems. Have followed the clymer manual. Removed the temperature sensor plug and tried to jumper around it, fan still didn't start.

Removed everything to get at the fan and it runs like a champ when connected straight to a 12 volt source. Bought a new temperature switch (relay) figuring that might be the problem. Still does not work.

Have checked the wiring harness lines continuity and all checks were good.

Has anyone had this problem or have any ideas?

[brucecha]

Did you check continunity on the negative pole to ground at the fan plug?
Double check all the fuses?

Bruce C

[dabk75s]

Yes, I have checked the fuses, they are all good (sorry didn't say that in the first place) and the continunity on the negative pole to ground at the fan plug is good also.

[jimajr37]

Try this web site; "Duck" is very knowledgeable about the "K" bikes. If he is unable to help, there are a lot of Tech "savy" guys that log on the the site.
http://k11og.org/forum/index.phpl.

[mwnahas]

Another link to try

http://www.ibmwr.org/ktech/fan-diagnosis.shtml

hope this helps

[dabk75s]

Thank you, I will try and see if the information there helps.

[dabk75s]

Thank you for the link, I will try this one also and see if anything helps.

[cjack]

I have a 1988 K75S that is having a problem with the cooling system fan starting. The bike is running great with no other problems. Have followed the clymer manual. Removed the temperature sensor plug and tried to jumper around it, fan still didn't start.

Removed everything to get at the fan and it runs like a champ when connected straight to a 12 volt source. Bought a new temperature switch (relay) figuring that might be the problem. Still does not work.

Have checked the wiring harness lines continuity and all checks were good.

Has anyone had this problem or have any ideas?

The temp sensor has two sensors in it. One is for the fan and one is for the engine management computer. There are two wires, both violet/green and they look at the resistance of the sensor resistances against ground. The sensor unit (in the water jacket at the front of the engine) has two resistance changing sensors in it, each with one end on ground and one end going to a vi/gn wire. To bypass the sensor, you have to ground the vi/gn wire. The sensors have a negative temperature coefficient which means they go down in resistance when the temperature goes up. They probably start out in the thousands of ohms when cold and are in the hundreds of ohms when hot. So you could also measure the resistance of the sensor, noting what it does from cold to hot as well.

[dabk75s]

Would like to thank everyone for their help. Went back through and recleaned all of the connections and with a new temp sensing switch (relay) the fan now works. Thanks again. Appreciate all the time and assistance.