AARRGG, I cant find info. on a low Gl1500 temp gauge..

[Droneh8tr]

Hey all,
I simply can't find info. I thought I had seen regarding a constantly low engine temp gauge and what to look at to fix it.
97 GL1500SE:
Temp gauge is almost always low, except when it gets particularly hot and the fan comes on. But even then it's maybe 3/4 range or less.

I've seen info. and would like to try what I saw, but can't find it.
Can someone send me some links to help me sort this out.
Thanks..

[gford]

are you sure you have a problem? My gage is normally on the low end and fans come on just over half way to hot

[Rambozo]

The fans should hold it at about 3/4 on the gauge, and will cycle there. Normal going down the road is 1/4 to 1/2 depending on conditions. If it's lower than that, your thermostat is probably not closing. Also be sure the gauge and sender are working properly.

[Sadanorakman]

The fans should hold it at about 3/4 on the gauge, and will cycle there. Normal going down the road is 1/4 to 1/2 depending on conditions. If it's lower than that, your thermostat is probably not closing. Also be sure the gauge and sender are working properly.

What Rambozo said: My gauge normally sits at about 1/4 when I'm riding unless it's really hot weather. This has always seemed too low to me, but I guess it's just how the gauge reads, as she runs really fine. It never seems to reach beyond 3/4 even when sitting on its stand idling for half an hour, as the fans cut in and brings the temp back down again every couple of minutes.

When I've been riding her recently (winter), I'm concerned of the road salt, so after a couple of hours riding out, I bring her back and let her idle whilst I hose her off and take a rag literally all over, then chamois her off.. She's sat there for a good 20 mins idling during this time, with the fans cutting in and out.

[DenverWinger]

1/4 scale appears to be the temperature the thermostat opens at.

[Sadanorakman]

1/4 scale appears to be the temperature the thermostat opens at.

I know that these wax-melt thermostats open proportionally i.e. the more heat, the greater they open, but I'm wondering how the phase-change temperature of the wax effects this.

Does anyone know the initial wax melt temperature, and how this corelates to the initial opening temperature at which coolant is started to be re-routed? Wondered if the initial opening temperature is literally at the wax melt-point, or somewhat above it, and therefore if it is the wax melt point that is used to set the required regulating temperature, or just the valve design such as spring pressure etc...

[Droneh8tr]

are you sure you have a problem? My gage is normally on the low end and fans come on just over half way to hot

I find it hard to believe that when my temp gauge doesn't even come close to the 1/4 mark (more like 1/8) during normal riding that this is proper. I could see how you have the same issue. It seems to me that their is resistance somewhere, or at least possible. Multiple components are involved to produce a gauge reading and I'm going to go through them.. hahah... as soon as I figure out what and where they are.

[Droneh8tr]

1/4 scale appears to be the temperature the thermostat opens at.

I know that these wax-melt thermostats open proportionally i.e. the more heat, the greater they open, but I'm wondering how the phase-change temperature of the wax effects this.

Does anyone know the initial wax melt temperature, and how this corelates to the initial opening temperature at which coolant is started to be re-routed? Wondered if the initial opening temperature is literally at the wax melt-point, or somewhat above it, and therefore if it is the wax melt point that is used to set the required regulating temperature, or just the valve design such as spring pressure etc...

1/4 scale seems resonable for an opening point, THEN, the valve would do its thing causing the gauge to settle near <=1/2 scale. (just trying to use logic)

[Droneh8tr]

Does anyone know the voltage thats being allowed through the temp. sensor that the gauge converts to a deflection? This seems like a piece of knowledge I should know.. (and yes yes before you say it... A repair manual will be ordered so I don't have to keep asking these questions, but you all are so darn smart)

So can I try to expedite things:
1. any input on the voltage at the sensor to produce 1/4, 1/2, 3/4 deflection?
2. DenverWinger has an interesting question on wax melt temp..

Actually... if you know of a link to an article that would be helpful also

Thanks for chiming in everyone.. I finally got my Wing on my lift for a teardown and questions abound...
WOW... the POs did some weird wiring. I hope to show some pics soon so you can live in my annoyance..

[Sadanorakman]

Does anyone know the voltage thats being allowed through the temp. sensor that the gauge converts to a deflection? This seems like a piece of knowledge I should know.. (and yes yes before you say it... A repair manual will be ordered so I don't have to keep asking these questions, but you all are so darn smart)

So can I try to expedite things:
1. any input on the voltage at the sensor to produce 1/4, 1/2, 3/4 deflection?
2. DenverWinger has an interesting question on wax melt temp..

Actually... if you know of a link to an article that would be helpful also

Thanks for chiming in everyone.. I finally got my Wing on my lift for a teardown and questions abound...
WOW... the POs did some weird wiring. I hope to show some pics soon so you can live in my annoyance..

I'm not trying to be obnoxious here, but maybe you were originally asking the wrong question, and I think you are now perhaps more correctly redefining that question with your most recent post.

Surely what you really want to know is: Is my engine temperature being managed correctly? Is the thermostat behaving as it should, or is it sticking open a bit, causing my bike to run cold?

So perhaps you'd be better measuring the resistance of the temperature sender with a multi-meter when cold, and then with a warmed-up engine, and looking to see what temperature that should relate to, as per the manual. It can be tested on and off the bike to get an idea of your real engine temp, or you could use a known good thermometer to measure the engine temp.

https://www.manualslib.com/manual/81794 ... l?page=155


I haven't looked closely into the temperature measuring system on the GL1500, but I get the feeling its probably just about as poor as the Fuel gauge!

The temperature sender will be a Negative Temperature-coefficient thermistor: These things are reasonably reliable solid-state devices, with a very tight manufacturing tolerance, and therefore very repeatable resistance/temperature profiles from one sample to another. They do however occasionally fail.

The moving Gauge however is probably quite inaccurate, and of reasonably poor manufacturing tolerance. I would also suggest that if you happened to have a slightly high-resistance connection somewhere between the two, then the gauge will probably read a bit low.

I genuinely only see the temperature gauge as giving a rough idea of temperature state, and expect it to read differently from one bike to the next. I think it's really about 'what's normal for your bike'.

remember the GL1500 electronics were designed in the early 1980's, and things like the temperature measuring circuit would have been using tried and tested technology that was much older still.

Sure we still use NTC Thermistors as sensors these days in modern vehicles, we just read their resistance more accurately with the ECU and can report an exact degree by degree temperature reading.

[Sadanorakman]

What I didn't appreciate is that the ECU takes the input from the water temp sender, and uses it for timing adjustment. I should have considered this, as many cars use an oil temperature sensor for this exact purpose. viewtopic.php?t=40095

Interesting to read the post toward the end that described the process of replacing the sender, and that:

'The new sensor went in easily. We then started the engine, without touching the throttle, and the idle was all over the place. Apparently it needs to run to remap the air flow so we let it run until the fans came on, and then turned it off. We turned it back on and set the idle at 800 rpm and it purred like a kitten!'

[Rambozo]

Wondered if the initial opening temperature is literally at the wax melt-point, or somewhat above it, and therefore if it is the wax melt point that is used to set the required regulating temperature, or just the valve design such as spring pressure etc...

It appears that the opening temperature is set by the wax formulation.

[Droneh8tr]

Nice write up Sadanorakman. Thanks for including the link to page 155.