Odd starting issue

[speedy231278]

I've always wondered if the gauge can actually reach the red or not, or if it's just symbolic. I suffered a leaking bottom rad on one occasion, and even that failed to get any further that it ever has in any other situation. Maybe the fan does a really good job of keeping the temp down from the astronomical end of things or the temp sensor for the gauge can't produce a high/low enough output to send the needle to the limit, but I can't imagine anyone fitting a temp gauge and sensor combination that don't produce a full scale deflection. I'm 90 miles from my Haynes at the moment, is there a test you can to do make sure the temp sensor is producing the correct output, or would removing the lead and grounding it cause the gauge to go full scale? To be honest, I'm not sure if the fan was cutting in or not. I'm pretty sure it's not one of those arrangements where the fan can keep running if the ignition is off, and I wear earplugs. I wasn't listening out for it after I got off the bike and tried to start it, however it was a little cooler by then and I'm pretty sure I'd have noticed it. I have a spare stat in stock and stat housing gasket on the way, as replacing it was on my to-do list as I've thought for quite a long time that the bike takes forever to warm up in the cold (like about 15 miles before the needle moves more than a fag paper or two) and it does seem to get hot a little quickly these days even with the rads cleaned inside and out. They're not perfect, but they are a very long way from being tatty. I wonder if the stat is stuck partially open.

My job next Saturday might end up being replacing it and cleaning the rads again. I did flush them about 15 months ago with some Speedflush. Not a lot of grot came out, however most of the grot that was removed turned out to be from the water pump, and was the only thing stopping the seal from leaking, so I'm a little reluctant to do that again in a hurry in case the replacement is suffering from the same. Unless anyone knows Speedflush to be harmful to some water pump seals, it's never done anything like that in anything else I've used it on! I only use premixed coolant or antifreeze mixed with distilled water, so hopefully the inside of things should be pretty tidy. I'll make sure the lower rad is squeaky clean on the outside too as they always get full of crap you only seem to be able to remove by taking the thing off.

[magg]

Fan power comes from the ignition switch and therefore is stopped when the ignition is off. Probably a precaution against a dud fan switch keeping the fan on after the owner has walked away and discharging the battery. Since you get gauge movement, it is functional, the temperature gauge sensor resistance should be:

50 C 130-180 ohms
80 C 45-60 ohms
120 C 10-20 ohms

You can test the sensor against the resistance values and also use resistors to drive the gauge and note the reading on the temp gauge.