Temp issue

[Steve]

Hi all,

I have an 86 5ktq that may be lying to me. It keeps flashing a temp warning but the gauge reads about 3/4 (between the dots). There is a gurgle sound and bubbling in the plastic tank that makes me wonder a bit.  

I thought I read in a post here that there are two sensors on this motor for temp. One for people temp meter and one for the computer. Is this right? It runs ok but is idling kinda cranky-like.(no pinging) 

Could it be just a bad sensor or is there a bigger problem about to bite me in the tail?

Thanks...