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Discussion Starter #1
Hi all! i've noted a strange behaviour of my 750 '93: when i switch on the headlights, the temperature indicator goes up visibly and the minimum RPM ad idle speed goes down a bit (50-100 RPM less) and vice versa when i switch off the lights. Few mounths ago (i've this problem since i've bought the bike) i changed the coolant; i suppose the old liquid was simply water with no coolant added -or it wasn't been changed for a lot of time- because it was dirt and dark but luckily it doesn't seemed to be contaminated with oil. Obviously the problem is still there -i suppose it's an electrical problem?!

Moreover i don't know if the fan works in the right way: it usually starts when the temperature indicator is almost at the red level and in this case it does it's job pulling down the temperature but sometimes (when it's very hot or i'm stuck in traffic) it starts when the temperature indicator is already in the red level and it's not able to pull down the temperature, unless i switch the lights off.
During the winter it not seems to be a problem because the temperature hardly goes up to the higher point; instead now with hotter season i have to switch off the lights eg when i stop at the traffic light so that the indicator turns down again.
The big problem is that in these case i don't know what is the "real" engine temperature and i'm afraid that this could cause damage to the engine.:frown2:

Anyone with similar experiences? Any suggestions?
 

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Ex-Lady Supermod
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I don't see how turning on your headlights would increase you engine temperature. If your cluster is like this, as long as you are not in the red you are good? When you changed the coolant did you flush out the system maybe even with a coolant system flush? Got it bled well with no air bubbles?
 

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I know things... A lot of things.
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I don't see how turning on your headlights would increase you engine temperature.
+1. I find it more likely, that the high beam drops the system voltage enough to cause trouble to the various sensors. You should verify that of course, by taking a measurement with a DMM at the battery poles. Take three measurements: before starting, after starting and after switching the high beam on, with the engine idling. Does the temperature jump around at all as the engine speed changes, say during a throttle blip?
 

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Discussion Starter #4
If your cluster is like this, as long as you are not in the red you are good? When you changed the coolant did you flush out the system maybe even with a coolant system flush? Got it bled well with no air bubbles?
Yes, my cluster is this one and everything seems to work fine if i don't switch on the lights! :serious: i flushed the system until the water was clean and then i added again the coolant; after that, since i didn't solve the problem, i bought a cooling system flush but i didn't use it yet because i thought that it isn't a problem of dirt or obstruction in the system, since it works fine with lights off!!

+1. I find it more likely, that the high beam drops the system voltage enough to cause trouble to the various sensors. You should verify that of course, by taking a measurement with a DMM at the battery poles. Take three measurements: before starting, after starting and after switching the high beam on, with the engine idling. Does the temperature jump around at all as the engine speed changes, say during a throttle blip?
The problem occurs as i turn on the low beam headlights; everything seems to work perfectly until then.. No changing in the temperature indicator when i speed up or down.. The only other change is in the idle speed RPM, increasing a bit when i turn the lights off and decreasing when i put the lights on :frown2: i don't know if it's relevant, but i mount a lithium battery..
 

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Try taking a couple of voltage measurements at the battery, as I suggested, and see what you get.
 
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