93 Accord temp gauge sticking on Hot

I have a 1993 Accord LX that is running fine and I just finished doing some preventative work because some things just had high mileage on them. Before I started I noticed the radiator fans were not coming on unless I had the A/C running. But the temp was staying in the middle of the dash temp gauge when the car was running with A/C on or off.
In addition I installed a nu radiator, nu radiator cap,nu heater hoses,nu coolant and a nu thermostat that I tested in a pan of boiling water before installing. I flushed everything. I am still waiting on a new temp sensor thats coming in the mail. I took the old sensor out and noticed it had some build up on it so I cleaned it off and reinstalled it.
When I put the car back together and started it the temp reading on the dash was in or just below the middle range but now the fans were coming on and it ran perfect. It has been a couple of days and now the temp gauge is going up to high but it is not a steady climb. It kind of bounces back and forth and then stays at the top.If I cool down the motor with a box fan sitting on top of it with the motor shut off for 30 minutes and then start the car the temp gauge starts in the middle but within a couple of minutes it is starting to bounce and then stays at the high reading.I have 168,000 miles on this car and this sensor might be the original one. I am going to change it as soon as the new one arrives but I wanted to see if anyone knows if this is just an old sensor that stopped working and then something I did to it revived it for a short period. The fans are coming on when I run the A/C but the temp still stays on high.The car seems to be running fine. Any thoughts?

I had mistakenly ordered the temperature gauge sensor when I really wanted the cooling fan sensor. The temperature gauge sensor is here at my house so I installed it and it seems to have fixed the problem. When the cooling fan sensor arrives I will install it because i don't know if sensors have intermittent problems as they get older. To me it is cheap insurance when I am doing the labor at my house meaning the labor is free.
One way I figured out how to test the system was when the temperature started going up i turned on the A/C which turned on both fans and the temperature went back down immediately. So the next time I sat there waiting and finally both fans turned on by themselves with the A/C off. I am still not comfortable with this so as soon as the new cooling fan sensor arives I will install it.
I did notice with all the new cooling equipt and a flush the temperature gauge is closer to cold than right in the middle like it was before. I had the same thing happen with my other daughters 99 civic.
I buy my genuine Honda parts at Majestic honda online. They are cheaper and I pay no tax. I live in Calif.

First thing to recognize is that there are temperature sensors (variable resistor) and temperature switches. The fans use temp switches and the guage uses a temperature sensor. So you can not mix them up and have things work properly.

To get my temperature gauge inside the car to go back down to normal readings I replaced the coolant temperature gauge sending unit. Before I did any work on the car the temperature gauge inside the car was working fine. I noticed when I took out the old or possibly the original coolant temperature gauge sending unit the element portion of the unit that goes inside the block had part of the finish or coating gone. I don't know if adding all new 50/50 coolant to the system might have caused this but like I said before the gauge worked fine before I started doing any work on this car. 170,000 miles on the motor -Thanks for everyones help on this.