Nuevo fresh water gauge

Currently in France with frequent 0% full on Sargent panel. Have checked connections to studs and suspect some corrosion between stud screws and wire terminals.
2 questions - If I remove tefminal screw will stud fall into tank leaving me with a hole?
What should be resistance between successive studs? I have laid underneath and measured approx 80 ohms between bottom stud and 25% stud and 8 ohms between 25% and 50% studs. I guess that 8 is the correct figure. I would be grateful if somebody could check theirs - Peter , I know you have a different van but probably same water system?
Alternatively, does anyone have Mark's email - I recall mark.burdett@autosleepers.co.uk but am unsure if it is mark. orm. and if autosleepers has a hyphen.
Thanks for any response.

Hi Ron,
Can't help with tank indication (my grey water is up the creek as well) but I have mburdett@auto-sleepers.co.uk as a good contact.

Good luck, John .

Thanks, John.
I have emailec Mark. He is very helpful.

Marks e-mail mburdett@autosleeper.co.uk or 01386853511
Boaby

Sorry, I see John has already supplied Marks email address .
Boaby

Should check other reviews before submitting mine, senior moment

Now home so today, having checked some details that Mark did not have with Sargent I cleaned up the ground contact on the tank. 
The studs are much smaller than I had expected. They are a bit like a small cavity rawlbolt fitting. The terminal screw goes into a rubber bush that fits into the hole in the tank. The terminal screw is also the stud. The connection wires are terminated with brass terminal tags that are zinc(?) plated.
I had expectex to bd able to remove the screw completely to release the terminal tag for cleaning. Sadly, this did not seem to be possible. Hosever, I was able to unscrew the terminal about 6mm which was enough to be able to gst a light file to the surface of the tag. The screw tightened again without difficulty to weather proof the connections and hopefully avoid corrosion between tags snd screws I put some transparent bath sealant onto the screw heads and over the tags on 4 of the 5 connections. The ground tag and the 25% and 50% tags were easy to deal with.  The 100% I did by feel but the 75% tag is inaccessible close against the chassis.
I suspect that, had I been brave enough,  I could have pulled any of the accessible studs out of the tank together with its rubber plug but I decided that it was not really necessary. The screw could be unscrewed enough to give access to clean the tag with a file but it then came to a stop, apparently captive within the rubber plug, and further screwing merely turned screw and plug.
Having cleaned up the ground tag I replaced water and it went to 25% as the level rose. Only time will tell if I have made a permanent cure but I am optimistic!

I know most people go for the tank end but my experience with the build of Sargent Panels (including my own) would go for dry or unsoldered joints in the control panel made a world of difference including less errors on other readings

I have had discussions with both Mark and Sargent. Corrosion of the bottom tag to stud connection seems the most likely. I hope that the clear silicone over the connection will prevent that recurring. That was Mark's suggestion - he said do NOT use tape over the connections. On mine the connections are exposed to the full force of road crud so it is not surprising that they corrode. I was very surprised at the small size of the studs. Also, I was expecting to be able to remove the stud completely but when unscrewing it came to a solid stop. I might have been able to pull the complete rubber plug out at that stage but it did not seem to want to come. If I do have problems in the future I will be tempted to replace studs with ones from Schaudt who supply Hymer.

I have just found this sentence in the Q&A's on Sargent's site in relation to the EC500:

Some tank arrangements use 5 stainless steel screws through the side of the tank rather than one probe assembly through the top of the tank.  These 50mm long screws can be affected by deposits in the same way as the top fitting water level probe.  To clean the bottom earth screw, unscrew the screw fully and then refit it.  The unscrewing process causes any deposits to be removed by the threaded insert that the screw is fitted in.  Also you can of course use a descaling solution.

That sounds helpful and sensible - as I said in an earlier post on this thread the screws do not come out completely - at least they do not appear to on my tank - but the unscrewing would clean any thread exposed on the inside.  However, my indicator is working OK at present after de-winterising. I will be interested to see what happens on our first outing this week.  The connections to my studs each have a blob of bath sealant over them.

I have just cleaned the main earth point and terminal ends on the chassis where a big bunch of hab wires are connected. It was pretty cruddy and although the indication is not 'fixed' they are all better

Hi Peter,

Photos follow 

The Earth point is on the nearside fwd face of the cross member on which the handbrake compensator mech is attached. Not the best of pics but a tad tight getting underneath where it is at the mo.
All best John.

I think that earth point is one of the MB provided ground terminals for after market builder use.

http://www.sprinter-rv.com/wp-content/uploads/2010/09/Bodybuilder_ground-terminals_NCV3.pdf

Yes it is  Now, why isn't mine all clean and white like that