[Chester Stone]

                Here is an explanation posted by Russ in 2012 which worked for me.  I have also attached his photos.

DIY Fuel Tank Sender
If at first you don't succeed..... I think I finally got it! When I purchased the coach the fuel gauge was not accurate and tests showed the problem was the sending unit. My tank is located behind a stainless steel vanity panel just below the bedroom slideout. Newell advised that if the tank had a square cutout with a mounting plate for the sensor it might be possible to do the job with the fuel and tank in place, but if no plate then it was a drain and pull the tank out a little way job. Mine had the square hole and plate. I ordered the sender at a considerable savings from here:
http://www.egauges.com/vdo_send.asp?...VDO_Adjustable

P/N is VDO 224-270 Right at fifty bucks at the time of this post. It looked just like the one I pulled out, but not so battered. It is about impossible to get the old one out or a new one in. Of course, there is not nearly enough room overhead to pull it straight up, so you must pull it at an angle and there are things in the way. The edge of the bay top and the hinge rod for the bay door are the biggies. I looked at removing the door and did not like my chances of doing it alone. I really had to push and turn and bend to get the replacement in, but I got a good reading for the low fuel level and thought maybe I had not damaged it during the install. But as soon as I filled up, the needle only made it to about 2/3 and I knew I had damaged it. I ordered another and soon was ready to try again.
This time I rigged my hydraulic jack with a 2x4 to press up on the axle rod giving me a little room. Holding the door part way closed, I was able to slip the new one in until the flange at the top of the sender contacted the top edge of the bay roof and was going to require bending to pass that point. I knew what would happen if I continued, so I stopped and stared at it for a long time.
Finally a light came on and I realized if I cut off just a small portion of the flange I would still have all the bolt holes less one and it should go in. Out came the Dremel and soon I had sliced off a segment of the flange and was ready to try again. It went right in - hurray! As I started to tighten it down I noticed it was tilted off to the side just a little and when I backed up I realized it was just touching the bottom of the tank before it was completely seated on the gasket. I just doubled up the gasket and it was fine. Tank is full and gauge agrees. I have attached a couple pictures. Hope this help someone sometime. Russ