Coolant Temperature Sensor Mystery

Kevin frazier said:
When you put it on tune ecu and start bike go to sensor page and watch your coolant temp sensor and when the fan does or not come on. This may show problem.
Click to expand...
I think it's intermittent though like yours. It's running fine now. You mean even so- might show an issue? I'll give it a go.

Hoping to do a 4 - 5 day trip next week (to be determined). I just changed the oil and put on a new rear tire. What else does she want?
 
Yeah, after bike has cooled, put it on tune ecu and start the bike, watch sensor page for that water temp sensor, note what temperature fan comes on and shuts off. Let the fan come on a couple times and see if the water temp sensor is behaving as should (lets just 190 degrees fan should come on and off when drop down below thermostat capability) and telling fan when to turn on and when to turn off. If it was the water temp sensor its gonna be bad, bike should overheat, i bet not intermittent like that fan controller like nashvegas fought.
 
Definitely overheating. In fact, on one occasion, didn’t turn it off soon enough and it was spitting out coolant. when I went into tuneECU, I could trigger both fans on with no problem. It was like the PWM Controller would have a hiccup every so often and ignore what the temperature sensor was telling it. I think if your temp bars are going up that part is working correctly. I wonder if they had a bad batch of PWM’s.
 
I think that only once in the last 30 years the the module/ecu said it was bad all the other time it blamed the sensors or actuators.
i have probably seen 100's of them bad
if you can get a resistance value you can use a resistor to check/to see if it reads correct on tuneecu as a test
you could use it value ? to trigger fan as a test. dont forget they get hot
 
Yep, I went down that rabbit-hole and it came down to the PWM “brain” not doing its job. But that’s not one of the checks. And, it got worse and worse. For $180 I figured it was easy money because the problem was becoming pretty serious/aggravating. She runs like a champ now.
 
Update: After many hundreds and hundreds of miles it hasn't occurred again, but I've been riding with the temperature sensor on display afraid I'll cook the engine. Either it was a freak incident with the sensor, it will rear its ugly head again later (probably after I finally turn off the temp display), or could it simply be that the coolant was low in the overflow tank- it wasn't dry, so not sure how that could be it and didn't take much to top back off.
 
Glad you're back on the road. The cooling fan should typically only be required when the bike is idling at a stop, never while while moving since enough airflow is available to remove heat from the radiator. If you are actually overheating it will be evident by coolant in the reservoir overflowing from the system as water expansion is exceeding system design. If the coolant in the tank is in band (and was at or above the MIN mark cold) and you get the warning check coolant tank level and you'll know whether it's a sensor or actual temperature by level indication.
 
Journeyman said:
It didn’t seem hot- just the gauge pegging. Then after a short rest it was ok.
Click to expand...
The sensor can fail in two ways. Since it's a resistance temeprature detector (RTD) type it will either fail high or fail low depending on the failure mechanism (short or open circuit). As a thumb rule always believe your indication, however when suspect, verify by other means. If your temp guage says the engine is over heating but seems normal, the physical check is what I outlined earlier, look for coolant puking out the overflow. If it's not puking then the detector is suspect and the only damage possible is to the radiator fan, not the motor. If the error is intermittent then it's an electrical issue, a connection is loose, corroded, or shorting to ground.
 
Good info- thanks. At this point not intermittent, just a one time occurrence. We'll see over time if that changes....
 
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