Temperature gauge reading

The temp gauge on my 84 F250 reads about where the M is on the gauge. Well when I accelerated the gauge quickly shot up to H and when I slowed down the gauge went back to M so when I got back to I took out the temp gun and it read 209 degrees at the cylinder heads. The top hose read 184 and the lower hose was 90 degrees. I don't consider 209 degrees overheating and I've already replaced the water pump and temp sending unit awhile ago. So is the IVR that is causing the problem?

If the IVR is the problem you will see the oil pressure and gas level do the same as the water temp since it feeds all three.  If not, then I think you have a short to ground on the wire running back to the tank(s).  (You don't have a signature so I don't know what year your truck is, what engine you have, etc.)

But your normal temp reading looks about right.  I have both the factory gauge as well as an aftermarket gauge, and the latter shows the temp running in the 204 to 208 range.  At the same time the factory gauge is pointing directly to M.

I had a problem with "sudden overheating" according to my temperature gauge. I wasn't sure what the problem was since the actual temp was not a problem. I did notice that when my temp read high, my fuel gauge also read higher than actual, but all other gauges were correct. Then, I started getting ridiculous reading on the tach a couple of times (like it was pinned past redline even though I was at idle). I was also experiencing an untraceable power drain on the battery when off.

I replaced the IVR with a new one for $40 and it fixed all of the problems. It's incredible how much that little piece of tin can mess up when it's not working.

I just pulled the new IVR ourt of my 84 because I upgraded the alternator. Want me to send it to you to see if replacing yours solves the problem?