Temp gauge not working - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 10-06-2011, 08:17 PM Thread Starter
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Temp gauge not working

I have a new bike(to me). My temp gauge is non operational. Any ideas?
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post #2 of 9 (permalink) Old 10-06-2011, 10:53 PM
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Hey Chris,

The temp sensor is underneth the gas tank. It might just be unhooked. If it's not, take it out and with the wire still connected submerge it in some very very hot water(be very carefull), leave it in the water a minute or so. Then turn the key on and with some thing to insulate your hand take the sensor out of the water and ground it to the thermastat housing. If it's good the temp gauge should register a reading. If not the sensor is bad.
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post #3 of 9 (permalink) Old 10-06-2011, 11:09 PM
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Quote:
Originally Posted by Chris32250 View Post
I have a new bike(to me). My temp gauge is non operational. Any ideas?
Download the Kaw vn750 service manual in Kanuck69`s first post here:
https://www.vn750.com/forum/showthread.php?t=17667

Many of us like the Clymer service manual as well.

Temp gauge test on page 336 of the Clymer manual.

1 -remove fuel tank. (Not sure, but you might not HAVE to remove the tank, but it will make seeing what you are doing easier.)

2- Remove right side steering neck cover.

3-Disconnect yellow electrical connector from thermostat housing.

4-Turn ignition switch to ON position.

5- Temperature gauge should read "C".

6- Attach a short jumper wire to the yellow wire electrical connector.

7- Touch, then release, the jumper wire from a good ground like the thermostat housing.
With the jumper connected the gauge should read "H".
Disconnect the jumper wire immediately or it can damage a good gauge.

8- With the jumper wire disconnected the gauge should drop back to "C".

9- If the gauge readings are correct it is ok, but the sensor may be faulty and needs to be tested.

10- If the gauge readings are incorrect, either the gauge is faulty or the wiring between the gauge and the yellow electrical connector is faulty. Inspect wiring and/or sensor.




There is a test for the sensor that involves suspending the sensor in a container of coolant, while it has ammeter probes attached to the electrical connector and grounded to the base, and heating the coolant slowly while watching a shop or candy making thermometer.

Simplified, what it says is that at room temp there should be NO continuity (infinite resistance)

At 80*C (176*F) there should be 42-62 ohms resistance.
At 100*C (212*F) the resistance should drop to 22-33 ohms.


If it fails any of these tests it must be replaced.

When you reinstall the (new or old) sensor, apply a light coat of silicone based sealant to the threads.

Put everything back on, refill with coolant and plug any wiring back together.

(Now is a good time to start using dielectric grease to protect all connections from moisture and corrosion.)

Hope this helps. Let us know what you find.
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TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
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post #4 of 9 (permalink) Old 10-16-2015, 11:20 AM
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Apologies in advance for digging another thread up from the grave...
Quote:
Originally Posted by OlHossCanada View Post
1 -remove fuel tank. (Not sure, but you might not HAVE to remove the tank, but it will make seeing what you are doing easier.)

2- Remove right side steering neck cover.

3-Disconnect yellow electrical connector from thermostat housing.

4-Turn ignition switch to ON position.

5- Temperature gauge should read "C".

6- Attach a short jumper wire to the yellow wire electrical connector.

7- Touch, then release, the jumper wire from a good ground like the thermostat housing.
With the jumper connected the gauge should read "H".
Disconnect the jumper wire immediately or it can damage a good gauge.

8- With the jumper wire disconnected the gauge should drop back to "C".

9- If the gauge readings are correct it is ok, but the sensor may be faulty and needs to be tested.

10- If the gauge readings are incorrect, either the gauge is faulty or the wiring between the gauge and the yellow electrical connector is faulty. Inspect wiring and/or sensor.
I tried test 7 last night and the gauge didn't budge. I then jumped the yellow/white and black terminals in the headlight housing and saw no movement then as well. Just so I'm clear - this does condemn either the gauge or the wiring between the gauge and the headlight connector, correct?

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #5 of 9 (permalink) Old 10-16-2015, 11:39 AM
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I dont have the manual in front of me, but most of the ground wires on the vn750 are black/yellow, not black.

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post #6 of 9 (permalink) Old 10-16-2015, 12:31 PM
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Quote:
Originally Posted by calebj View Post
Apologies in advance for digging another thread up from the grave...


I tried test 7 last night and the gauge didn't budge. I then jumped the yellow/white and black terminals in the headlight housing and saw no movement then as well. Just so I'm clear - this does condemn either the gauge or the wiring between the gauge and the headlight connector, correct?
yellow/white needs to be jumped to frame ground on gauge side of the connector inside the headlight housing. (when you unplug the wiring harness, you are unplugging the ground from the gauges, so technically not going to get continuity by just placing a jumper back into a broken circuit.) If the needle pegs out then you have a problem with the wiring between then sending unit and the headlight, if nothing happens then you have a bad gauge.
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post #7 of 9 (permalink) Old 10-16-2015, 02:08 PM
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Quote:
Originally Posted by slimvulcanrider View Post
yellow/white needs to be jumped to frame ground on gauge side of the connector inside the headlight housing. (when you unplug the wiring harness, you are unplugging the ground from the gauges, so technically not going to get continuity by just placing a jumper back into a broken circuit.) If the needle pegs out then you have a problem with the wiring between then sending unit and the headlight, if nothing happens then you have a bad gauge.
The connectors weren't unplugged, I just jumped them using a jumper wire pushed into the metal wire terminals inside the connector body. That said, it does look like I should have jumped yellow/white to black/yellow, not black. I'll check again this evening.

Thanks to both responders for the suggestions.

1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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post #8 of 9 (permalink) Old 09-12-2017, 08:20 PM
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I know this is an old thread, my sincere apologies for resurrecting it. I have a question relevant to test seven though. When the jumper is connected to ground, should the needle swing immediately to H? When I did it (went to negative terminal of battery) the needle swung over, but it took its good sweet time. 15-20 seconds I'd say.

I'm doing this test to chase down an overcooling/potential loss of coolant issue, and I need to determine if my gauge is even close.

1993 Kawasaki Vulcan 750

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post #9 of 9 (permalink) Old 09-17-2019, 12:41 PM
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Quote:
Originally Posted by wmdaricthompson View Post
I know this is an old thread, my sincere apologies for resurrecting it.
Do not apologize to use the good/old thread. It is much better to have it in one place than on different threads.

I have the same problem. A needle is dead. I will check it these days.

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