TOPIC:

I'm hoping that I'm not having a senior's moment but I also have it in the back of my mind that Scotch came across this some time ago.

Yup ! It was me. Seems everything else has been covered so per "the Bible", check the voltage output of the instrument voltage regulator.
It's a simple circuit. This is a similar schematic:



If it checks-out, test the temp. gauge sender.

scotch wrote: I'm hoping that I'm not having a senior's moment but I also have it in the back of my mind that Scotch came across this some time ago.

Yup ! It was me. Seems everything else has been covered so per "the Bible", check the voltage output of the instrument voltage regulator.
It's a simple circuit. This is a similar schematic:

If it checks-out, test the temp. gauge sender.

As I understand it, the job of that voltage regulator is to supply a constant & stable 7 volts DC, irrespective of battery voltage, to the fuel & temperature gauges, so that the needles don't move with the constantly changing battery voltage?

And this is a prime example why I choose to be part of a Forum after retiring 12 years ago. Keeps the brain in check. So maybe a senior but not ready for seniors moments quite yet (maybe next week? ).

Kawboy wrote: Here to help if I can Don. Just going to throw out some logic for consideration.
The engine thermostat measures and reacts to engine temperature and no matter what the ambient temperature does not react to ambient temperature so whatever you're witnessing on the temp gauge is what's happening in the engine.
When the thermostat opens and exchanges coolant between the rad and the engine, the coolant headed to the rad is around 180 F and the ambient temperature around 80 F. That differential, the greater it is the quicker the exchange of heat but in theory even if it was 140 F outside, there would still be a transfer of heat and unless the creation of heat is greater than the expulsion of heat, the thermostat should be able to maintain the engine temp at operating temp.
In the 50 years of wrenching I don't think I've had to change out more than 3 thermostats but in every case where I did, that was the problem. I still think that for whatever reason, you're experiencing a bad thermostat, be it a weak thermostat or a misfitting thermostat due to some dimensional issue.

The only other thing that comes to mind and don't hold me to this is I have it in the back of my mind that the fuel gauge and thermostat work at a reduced voltage from system voltage due to the indicator needle gauges. I'm hoping that I'm not having a senior's moment but I also have it in the back of my mind that Scotch came across this some time ago. That being said, are we sure that the indicated temp is accurate? or are you chasing a ghost?

The thermostat should be here in a week or two. No worries, no hurries. It's supposed to above 80F tomorrow, will try another ride in hotter weather.

I understand the heat generation vs cooling idea, and agree if cooling systems are working correctly, should be able to shed excess engine heat to ambient via the heat exchanger (radiator). My thought from previous post that maybe at 60 F ambient, the cooling is greater than heat production, thus preventing the thermostat from fulling closing the bypass, e.g. the t-stat is providing bypass flow to prevent the engine from running too cool. Then, when ambient conditions rise, and cooling capacity diminishes, engine heat increases, the t-stat goes into 'full cool' mode and is why the needle dropped about 2-3 widths when ambient temps rose? Noticed this several times yesterday.

Interesting thought on instrument cluster voltage regulator. I noticed yesterday my system voltage ramped from 12.0 to 14.9, apparently randomly, as not into the fan, or knowingly adding additional load. So charging will be next. This bike has dual alternator setup. Of note to is I connected to a brown wire near headlight for voltage sampling. Will move it directly to battery after procuring appropriate connectors and cabling.

Phil wrote:

scotch wrote: I'm hoping that I'm not having a senior's moment but I also have it in the back of my mind that Scotch came across this some time ago.

Yup ! It was me. Seems everything else has been covered so per "the Bible", check the voltage output of the instrument voltage regulator.
It's a simple circuit. This is a similar schematic:

If it checks-out, test the temp. gauge sender.

As I understand it, the job of that voltage regulator is to supply a constant & stable 7 volts DC, irrespective of battery voltage, to the fuel & temperature gauges, so that the needles don't move with the constantly changing battery voltage?

I assume the regulator is in the instrument cluster? Off to the FSM and Thank You!

Stiggy wrote: I haven't had cooling issues but I temporarily fitted a cheap digital temperature indicator as a cross check. They are cheap but accurate enough for this purpose. Lots on fleabay. They have internal battery so no wiring needed.
Here's the item number of the one I got. 274386235926. Beware some similar looking only go to 70 deg c.

Most i ever saw was 89 deg c in traffic but usually about 86 at mach 1.
Note... mine is a UK ZG1300 DFI.


I used a blob of silicone sealant to attach the sensor to the coolant outlet, then added a piece of insulation about 2 x 2 inches to prevent any false reading due to air cooling.

Great idea! You know, IIRC I have some T/C wire and a T/C portable reader.. Off to the drawers!