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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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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.
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.
Linkmeister Supreme
Quote:
Originally Posted by Chris32250
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I have a new bike(to me). My temp gauge is non operational. Any ideas?
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.


1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)
H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15
TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
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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?
Quote:
Originally Posted by OlHossCanada
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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.
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.
1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
Super Moderator
I dont have the manual in front of me, but most of the ground wires on the vn750 are black/yellow, not black.
2005 VN750
Sold 11-27-17
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?
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?
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.
Thanks to both responders for the suggestions.
1986 VN750 27k miles
1999 EN500 32k
1983 GL650i in pieces. Someday it will ride again.
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.
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
Garage is good. Garage is Therapy. Garage is life.
Quote:
Originally Posted by wmdaricthompson
View Post
I know this is an old thread, my sincere apologies for resurrecting it.

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

Ride a day, keeps boredom away
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