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Hello everybody,
first ride today with my z1300 after top end rebuild. The problem is, that the fan doesn't work even when water temp is at max. When I pull the wire from the thermo switch (the one on right side of the engine in the head) and connect it to ground no action as well. Am I making a mistake? The resistance of the thermo switch is infinite. The connection from the thermo switch to the relais under the seat is ok. What to check next?
How can I test the relais and how could I switch on the fan manually?
A lot of questions! Many Thanks in advance for your support!
Karl

I don't have a proper answer for you but mine obviously had the same problem and the previous owner has wired the fan direct to the right handlebar on/off switch which I presume was the engine kill switch, its a neat way of having control of the fan so you can put it on when you know the bike is about to get hot in traffic etc and no worry it isn't going to kick in.

the wire from the sender is just a trigger for the relay
check the fuse is ok, then check you have power to the relay.

Thanks for the input. I found the reason today after extended research:-) The Wiring harness in my bike (or the whole bike) is from a 1982 A4 US/Canadian KZ1300. I studied the wiring diagram and found something I didn't understand. The fan is supplied by a blue (hot) and the black/yellow (ground) wire. The blue one goes to the relays. The relays is connected to red/black (two hot wires) and the red/white wire which goes over the fan thermo switch to ground. The red/black goes to the fuse box over a 10A fuse to a white/red wire which must be 12v plus. BUT!!! In the diagram in the manual it seems to end in the 9 pin connector of the fuse box in the nowhere! No connection to 12V plus!? No, after thinking again and again I saw this little dot which connected the 10A fan fuse to the 30A Fuse which is connected to the battery with the second white/red wire and goes with a white/black wire to the main switch. Somebody rewired the fusebox and forgot to reconnect the connection between these two wires!
I reconnected the two and the fan is working perfectly! As you said always follow the ground and the 12V path:-)
Thanks
Karl