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DannoXYZ · July 4th, 2018, 05:36 PM

Hi Kelly and welcome!

You've been mis-informed. Here's what you want to do:

1. test thermostat - remove thermostat and place in pot of room-temp water with thermometer. Turn on heat (high) and note temperature where thermostat opens fully. Should be around ~150F.

2. test temp-gauge sensor (on thermostat housing, right side) - remove temp-gauge sensor and place in pot of room-temp water with thermometer. Turn on heat (high). Measure resistance (impedance) of sensor at various temps. At 175F = ~51 ohms, at 210-F = ~28 ohms. This is known as NTC sensor, negative temperature coefficient, sensor-resistance decreases as temperatures increase.

3. test temp-gauge sensor wiring and gauge itself (on thermostat housing, right side) - key ON, with disconnected sensor wire, gauge should read C. Connect sensor-wire to chassis-ground, gauge should read H.

4. test fan thermoswitch (left side of radiator, your picture above) - remove fan thermoswitch, place in pot of room-temperature water with thermostat, turn on heat (high) and measure continuity between centre terminal and metal case of sensor. Note temperature when switch closes/connects (ON, no resistance, full continuity) ~205F. Turn off heat and dump in some ice-cube to cool water. Note temperature when switch opens/disconnects (OFF, infinite resistance, no continuity) ~195F.

5. test fan thermoswitch wiring (left side radiator, your picture above) - connect disconnected thermoswitch wire to chassis-ground with short-jumper, fan should turn ON.

FAN NOT RUNNING WHEN THERMOSWITCH WIRE GROUNDED

6. test fan - disconnect wiring-connector at fan. Apply +12v to one terminal and other terminal ground to chassis. Fan should run!

7. test fan relay - trace fan-wring to fan-relay, back-probe connector leaving relay connected.
- measure voltage at white wire going into fan relay, should be +12v full battery voltage
- fan-thermoswitch wire grounded, measure resistance (impedance) on relay black/yellow yellow wire to chassis-ground. Should be zero-ohms, full-continuity.
- fan-thermoswitch wire grounded, key ON, measure voltage at relay blue wire, should be +12v full battery voltage

8. test fan wiring - leave fan-thermoswitch wire grounded
- measure resistance between black/yellow terminal of fan-wiring connector to chassis-ground. Should be zero-ohms, full continuity.
- key ON, measure voltage at blue terminal of fan-wiring connector. Should be +12v full battery voltage

Do in order, There are many difference independent components that work together in cooling system. These test uses boolean-logic and process-of-elimination to determine which part is bad. There may be more than one bad part, so do all tests.

July 4th, 2018, 05:36 PM	#2
DannoXYZ ninjette.org certified postwhore 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	Hi Kelly and welcome! You've been mis-informed. Here's what you want to do: 1. test thermostat - remove thermostat and place in pot of room-temp water with thermometer. Turn on heat (high) and note temperature where thermostat opens fully. Should be around ~150F. 2. test temp-gauge sensor (on thermostat housing, right side) - remove temp-gauge sensor and place in pot of room-temp water with thermometer. Turn on heat (high). Measure resistance (impedance) of sensor at various temps. At 175F = ~51 ohms, at 210-F = ~28 ohms. This is known as NTC sensor, negative temperature coefficient, sensor-resistance decreases as temperatures increase. 3. test temp-gauge sensor wiring and gauge itself (on thermostat housing, right side) - key ON, with disconnected sensor wire, gauge should read C. Connect sensor-wire to chassis-ground, gauge should read H. 4. test fan thermoswitch (left side of radiator, your picture above) - remove fan thermoswitch, place in pot of room-temperature water with thermostat, turn on heat (high) and measure continuity between centre terminal and metal case of sensor. Note temperature when switch closes/connects (ON, no resistance, full continuity) ~205F. Turn off heat and dump in some ice-cube to cool water. Note temperature when switch opens/disconnects (OFF, infinite resistance, no continuity) ~195F. 5. test fan thermoswitch wiring (left side radiator, your picture above) - connect disconnected thermoswitch wire to chassis-ground with short-jumper, fan should turn ON. FAN NOT RUNNING WHEN THERMOSWITCH WIRE GROUNDED 6. test fan - disconnect wiring-connector at fan. Apply +12v to one terminal and other terminal ground to chassis. Fan should run! 7. test fan relay - trace fan-wring to fan-relay, back-probe connector leaving relay connected. - measure voltage at white wire going into fan relay, should be +12v full battery voltage - fan-thermoswitch wire grounded, measure resistance (impedance) on relay black/yellow yellow wire to chassis-ground. Should be zero-ohms, full-continuity. - fan-thermoswitch wire grounded, key ON, measure voltage at relay blue wire, should be +12v full battery voltage 8. test fan wiring - leave fan-thermoswitch wire grounded - measure resistance between black/yellow terminal of fan-wiring connector to chassis-ground. Should be zero-ohms, full continuity. - key ON, measure voltage at blue terminal of fan-wiring connector. Should be +12v full battery voltage Do in order, There are many difference independent components that work together in cooling system. These test uses boolean-logic and process-of-elimination to determine which part is bad. There may be more than one bad part, so do all tests. Last futzed with by DannoXYZ; July 8th, 2018 at 09:16 PM.