water temp sensor

[carlb]

I have a 1988 Vogue Diesel on a Crown chassis powered by an 8.2L turbo detroit diesel. I was about 4 miles from home when the water temp alarm and chime came on.  The water temp gauge was normal, about 195.  I pulled over and checked it out but found nothing unusual, no leaks normal temp. I waited an hour till the temp gauge was down to 80, but the alarm did not reset. I drove back home and the temp gauge read normal. Back home I started looking around, found the temp gauge sending unit right in the water pump manafold. My problem is that I cannot find any other water temp sensors. Anyone know where a second sensor might be located?