temp display of my v-tec is not correct!

Hello everyone, a few weeks is that the temperature of the display of my v-tec 2003 starts giving erratic and discontinuous values​​, increased from 60 to 81 to 75 to 60 degree, the display show a number for 4-5 seconds, sometimes swing between two numbers with about 10-15 degrees difference between them, then it all comes back after a period standard and follows the exact temperature of the engine! The engine temperature is running ok and I did this summer long journeys often above 500 km a day and never any trouble, have you got any idea of my problem?
I replaced this week thermostatic valve and temperature sensor thinking it was that and instead the problem remains, yesterday i finally changed all the instruments, speedometer tachometer ecc, nothing to do, the problem remain!
this video show the problem:

https://www.youtube.com/watch?v=-Qblt6Co81w

I travel a lot with my vfr, this is my second VFR v-tec always of the same year 2003.
The last year I did a tour in the Arctic Circle and NordKapp and I traveled 13,000 km along the Norwegian and Finland coast.
At the end of the trip the thermometer of the temperature began to make frequent changes to these numbers.
So during this winter because the bike has 40000km I bought the stator, the R / R, the thermostat and the water temperature sensor, gauge, and I changed the pieces (Home work with passion) and checked everything,
but the problem is still the same. so I think it's a problem with the wiring or grounding.
What do you think?

Thank you very much for your cooperation,
Lorenzo

 

If you've replaced the temperature sensor and the instruments, that leaves only the wiring. A very small increase in the resistance of the temperature sensor circuit can cause an errant reading. Have you tried cleaning all of the connectors in the path of the temperature sensor's signal to the instruments? Also, it doesn't hurt to clean all the grounds of the VFR. Good luck!

 

If I was a VFR and you took me to the Arctic circle, I'd probably punish you for the experience too... :tongue:

 

My 2004 does the exact same thing. I've replaced all the parts you've replaced (except for the instruments) and the problem persists. The fan comes on when I'd expect it to and the engine doesn't seem to be running any hotter. I've talked to a few motorcycle guys (not professional mechanics) and the consensus is the next step would be check the wiring specifically the grounds. I haven't don't this because I'm taking a little hiatus from riding (I moved to NYC) so the bike is in storage until I get back to TN.

Sorry no help from me but its good to know I'm not the only one that's experienced this problem.

 

So I'm not the only one!
Yesterday I removed the front and the instrumentation and I cleaned and checked all the wiring, also all the negative.
Always the same display, I post a new video to show you...

Vfr temperature display incorrect - YouTube

So now what can I check?
Thank you very much for your cooperation

 

That is weird symptom have you talk no any Honda mechanic in your area to see if they know any thing?

 

Yes, I tried to Honda mechanic but they have no idea (I tried two mechanics)...
My question now is if this wrong signal can damage the engine or if I can safely go on a motorcycle for a day and the problem is with the display only,
what do you think abaut this...
the centraline of the engine receive the wrong signal?

 

I am sure you can install after market sensor to display the temperature and other info as well.
I know it is annoying :chaingun:
https://www.denniskirk.com/shindy/digital-water-temp-gauge-17850.p40663.prd/40663.sku

 

Do you have an electrical multimeter that can measure resistance? The coolant temperature sensor should read 6.8 to 7.2 kΩ @ 50C, 2.1 -2.6 kΩ @ 80C, and 650 - 730 Ω @ 120C. Even though it is new and is probably okay, it would be a good check to verify that it is okay.

Then the issue appears to be an erratic fluctuation on the gauge. The sensor signal is routed to the display gauge thru an analog-to-digital converter on a circuit board in the instrument unit. If you can remove the covers and inspect the traces from the main connector across the circuit board you may find cracked solder joints at the base of pins. Use a magnifying glass to find cracked joints and touch them up with a hot solder iron to repair.

The other high frequency failure besides cracked solder joints is failed aluminum electrolytic capacitors. Sometimes it is evident by the puffed up dome on the top of the cap. They only last 5 to 10 years before becoming 'leaky' and unable to hold voltage as designed. If the board supply voltage is fluctuating due to a bad cap, then the sensor signal will likely be affected and fluctuating also. Caps can be desoldered and removed and tested to find the culprit, or just remove and replace all of them--they are cheap and you don't really care which one is defective unless you work in electronics... Good luck and let us know what you find when you fix it.


Yes you can ride it. The ECM uses a different portion of the sensor to read coolant temperature. The problem is likely not in the sensor but on the circuit board in the instrument unit.

 

thank you very much for your perfect explanation,
I had also thought about a problem instrument.
For this reason I bought an instrumentation of a vfr that he had an accident to try,
but the problem remains the same.
I changed the sensor with new one and I tested the resistance to the old sensor and is perfect,
so as you say the problem wil be in the electric circuit...
I hope to find the problem.
Now I do not know where to look for the fault!