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Old October 3rd, 2019, 09:06 PM   #4
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

Posts: A lot.
MOTY - 2018, MOTM - Nov '17
Best way to test fuse is to measure resistance (ohms) across legs. https://learn.sparkfun.com/tutorials...ing-resistance



Thermoswitch is like regular switch, except instead of using your finger to flip it on & off, it's done by coolant temperature. At low-temps, switch is open and no current flows. At high-temps, switch closes and current flows to turn on fan. Like with fuse, connect multimeter to measure resistance across terminals of thermoswitch. Measure resistance at room-temperature. Then put thermoswitch in pot of water and bring to boil. Measure temperature where resistance changes from previous state. Thermoswitch needs to be immersed in coolant to work.



1. You can test fan-operation by unplugging connector from thermoswitch. Then use short piece of wire, bridge two terminals inside connector. Does fan turn ON (with key ON)? If NOT, you've got two possibilities:

2. fan BAD? Disconnect fan connector. Using test-leads, apply +12v & ground to fan. Does it spin? If YES, you've got problem with wiring between fan and battery.

2. wiring BAD? If fan spins when power applied directly, but NOT when thermoswitch plug is shorted, then power is not making it from battery to fuse to thermoswitch connector. Test by tracing flow through fan-circuit. Measure voltage at following points:

- battery +positive terminal
- white wire leaving starter-solenoid
- white wire entering fuse-box
- white/blue wire leaving fuse-box (after fuse#7)
- white/blue wire entering thermoswitch-connector
- (short two terminals in thermoswitch-connector, then continue measuring voltage)
- blue-white wire leaving thermoswitch-connector
- blue-white wire at fan connector

Where +12v disappears will point to problem between there and previous test-point.

Last futzed with by DannoXYZ; October 8th, 2019 at 08:21 PM.
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