Thermostat, gauge, sending unit, or 7-volt regulator?

[Jcbailey_11]

I recently bought a 78 gl1000 and the previous owner told me even though the temp gauge reads hot, it's actually not and he even had it heat-gunned at a honda dealership just in case. He didn't get around to actually fixing whatever the problem was though. The fuel gauge works fine so I don't think it's the 7-volt regulator. If he actually did have it tested with an infared gun and the temp was indeed fine, what could it be? I have a new thermostat but I'm starting to think it couldn't be the thermostat if the engine isn't actually running hot, just the gauge is reading hot.

What should I do?

[flash2002]

Hi jc, I think if the rest of the gauges work, I would suspect the temp switch on the motor. One thing, does the gauge go to hot on start up or gradually goes up ?

[Jcbailey_11]

gradually goes up but it doesn't take long and no matter the riding conditions it never reads "cooler" than about the white line immediately before the red zone. I know this might be a noob question but what does the temp switch do?

[flash2002]

JC, The temp sensor changes resistance with the temp so when the temp goes up the resistance changes making the gauge go up. Make shure your rad is full, and one thing to check is the thermostat, it might be defective.

[Placerville]

You said, "I have a new thermostat but I'm starting to think it couldn't be the thermostat if the engine isn't actually running hot, just the gauge is reading hot." Are you saying that you installed a new thermostat or that you have one in your possession? The reason I ask is, are you sure there's a thermostat installed in your bike?

Some owners have the opinion that removing a thermostat makes their bike (or car) run cooler as there's less restriction and the water flow faster. Actually, that's not the case at all. Thermostats have an important job to do. Part of which is to create just the right amount of restriction to keep the coolant flowing properly balanced.

Before replacing your temp sensor (it's very tough to get to) first, cover all the basics. Make sure you have the correct amount non-silicate coolant e.g. Peak Long Life, mixed at a 50/50 blend with distilled water. Ensure that your thermostat exists and is in good working condition. If your not sure it's working properly, replace it, their inexpensve. Make sure your radiator and hoses are clean, your rad cap seals properly and your reservoir is moving coolant in and out as it should. If all of those things check out, your cooling system is working properly.

If after all that, you find your gauge is still reading hot, it's your temp. sensor.

[Jcbailey_11]

I replaced the thermostat, flushed the cooling system, and put new 50/50 non-silicate coolant in it today and when I warmed it up it did the same thing.

Temp sensor?

[Placerville]

Yes or no, it's your next logical step. If that doesn't fix the problem (and I really hope it does), the only thing left is the gauge. If that's the case, you have two choices, 1. Buy a used gauge on eBay or, 2. Send yours to an expert to be fixed.