I have looked around the site and haven't been able to find the answer I am looking for. My Riv's fuel pump is working fine, but the dash gauge is not reading correct, sometimes reads correct down to half a tank, but then fluctuates back to full. I already checked source voltage and verified ground at the pump harness. Has someone else had this problem in the past? I know I would have to pull the pump/sender, not that big of deal, I just wondering if anyone has repaired the sender to function correctly again, or is it just a better idea to buy a new pump unit for $300+ ? Thanks for any help!

Welcome to the site.
Yes, others have had the same problem. The sending unit (rheostat) goes bad.
Try typing "Fuel Pump" in the Search engine on this site, there are multiple write ups concerning replacing just the sending unit and some info on getting a pump assembly for less than $300.00.
I found an OEM AC/Delco unit new on EBay a while back for $ 75.00, but that could have been just a fluke.

What year is your car. Add some info to your signature, it helps us help you better.

Thanks for the info, I will search. Sorry I forgot to mention, 1997 Riv.

After doing some research on here, I figure that is probably the best idea. I haven't seen anything off someone fixing just the sender. Will replace it all this summer.