High water temp alarm chirping

My high water temp alarm started chirping last night. I didnt even know what was making the noise for awhile because it would just chirp but the light didnt go on. I started seeing the warning light go on finally enough to read what it said. My first thought was it was bad wiring because it seemed to only do it when I hit bumps. Today it did the same thing at the start of the day. I turned the engine fan on and it goes away unless I come to a stop (3 times today anyways) exept just now when I let it idle for about 10 minutes before I turned it off. My gauge reads the water temp is only 175-180(normal). The top pipe on the radiator is 175° and the bottom pipe is 115°

A little history. Not too long ago(a month) I had the oil cooler replaced because of oil in the coolant. They flushed the radiator but theres still oil in there. I asked about this and they said just to flush it out the next time I get a PM done that one flush isnt going to get all the oil out. I also replaced to thermostats and water pump about 8 months ago.

Im confused beacause my gauge reads normal but the warning light chirps at me (it doesnt come on fully).

 

The trucks been sitting (turned off) since I posted this a couple of hours ago and right away its chirping at me. The water temp was around 100° when I started the truck.

 

I agree. Maybe someone can explain the fan phenomena.

 

Same thing today.

 

The fan doesnt kick on until it gets to 210° but it very rarely ever does get up that high. I am guilty of turning it on sooner but I havent pulled any hills lately.