1983 310 guages

[Bfrank]

Ok folks I need to pick someones brain on this My 83 310 I am restoring has a problem with the fuel and volt meter guages.
The fuel guage is pegged out past the full mark like it gets no voltage from the sending unit in the tank. I removed the wire from the s pole on the guage and put a ground on the guage S
pole and the needle moved to E so the guage is good. My question is what next I found a cutout in the floor somewhere
over the fuel tank and thought this was an access to sending unit
but is covered from the under side by Alum skin not sure if I want to cut this out yet to see what's under there. the other guage problem is with ign in the on position the volt guage pegs out
past the scale on the guage and in the off position the needle
moves to 13 or 13.5 volts on the scale with the engine running I
put a vom on the engine start battery and it is getting a good
13.6 volt charge the coach batterys are new and getting the
same reading with the engine running so It seems that the
alternator is doing it's thing but not sure if the two are related to some bad wiring or if the volt guage is ok yet. any suggestions
from someone who has more of this type of troubleshooting
experience would be greatly welcomed I'm not sure what to check next. Thanks in adv if you can help.

[FrankR]

Fuel gages are easy to check and repair. These devices are controlled by a float in the fuel tank. The tank unit is merely changing the ground resistance to the dash unit. If the gage shows full, the single wire from tank unit must be touching the vehicle frame/sheetmetal/ground or sending unit is bad. Identify the color wire going to fuel tank from the dash gage. Near the tank unit, cut the wire where it will be easy to repair. Test gage operation again. If gage works OK sending unit is bad or has some problem. In our shop we have a old fuel tank sender, that we connect to do a quick test. You may need to remove fuel tank to inspect/repair tank sending unit.
A DC volt meter is nearly indestructible.. My SWAG is the wiring is just slightly incorrect. The volt meter needs on 2 connections, as a +12 volt positive connection and a - negative connection anywhere to chassis ground. Most factory meters are at least 20% inaccurate. The digital gages are really kool but pricey and fussy.

[Bfrank]

Thanks for the input. The problem is going to be getting to that
fuel tank sending unit because as I stated I guess I'm going to have to cut out the skin under the plywood cutout to even see if that gets me to the fuel tank sending unit as for removing the tank the straps that hold it in place are near impossible to get
to the nuts that hold it in place. It looks to me like I may have to remove the rear storage box that houses the ac pwr cord and the blk water tank hose just to be able to get a socket on the
strap nuts to remove the tank. Have you been into one of these
units or would you go ahead and cut through the underskin to
access the sending unit ? I have rolled around under the coach
looking into wiring harnesses but have yet to find the pink wire
that the schematic shows goes to the sending unit. but it's
gotta be in there somewhere.

[FrankR]

My view...... I'd spend lots of time looking for the elusive sender wire before any cutting or removing. Move the search closer to the dash. Find the wire and cut to do the checks. Go get another GM sender at a salvage yard. Use a car or truck of about the same year. On several occasions I have removed the fuel tank only to find the wire was pinched when a hitch was installed. Removing the fuel tank is not fun and very dirty. This task usually requires at least 2 guys after the tank has been drained of fuel... It could also be that the fuel sender float is stuck in some position. Most senders can be repaired without replacement. Airstream seems to have used a lot of GM electrical parts and maybe the same drawings and color codes.

[thenewkid64]

You may want to look for the wire loom that runs inside the drivers side frame rail. This is a bundle of wires covered in a woven wrapper. This loom would have been installed by GM and contains all of the turn sigal and brake light wires. It should also contain the wire to the fuel tank. Tapping in here would allow you to test Frank's theory prior to dropping the tank.

The only other explaination is you have a magic MH that nevers needs fuel.

[Bfrank]

Frank That photo looks neat compaired to what I'm dealing with
and I gotta stand on my head just to get to it ! Thanks for the
input I'll give everyones suggestions a try before I saw up the floor and get to trying to remove the tank. I would just rather not
have to do all that but whatever it takes I just want it to work so
I can move on the next item on the list ( which is quite long at
this time

[PeterH-79MH]

Bfrank,
I dropped the 80 gal tank on my 79 MH.
I drove it to near empty before pulling the drain plug. It still had 12 gal in the tank. I drained it into a modified 5 gal bucket (with an access slot cut on the side to be able to reach in and replace the plug).
Be aware that just by dropping the tank straight down, you may still not be able to reach the sending unit. You may have to slide the tank out from under the vehicle. Careful measurements and ramps for the rear tires may be needed.
Gasoline weighs 6.17 pounds.
With 10 gal left in the tank, you are looking at 100 pounds plus.
The bolts for the straps were hard to reach and for some reason, I did not have the proper socket in my assortment. I ended up getting a 19mm socket from sears that is 1 5/8" long, which allowed it to fit over the threat to reach the nut.
If you drop the tank replacing the rubber fuel lines should be included.
Most of the wires are running on top of the drivers side chassis frame.