Water tank sensors

[Bren360]

Hi i have a Timberland endeavour and i am having problems with my waterworks, i thought it was an air lock but i have found out today that my water tank reading is always showing 75% full because i have faulty sensors, so it is in fact empty, i have only used the van twice so im clueless, is it a specialist job, as the company is very far away,or could any motorhome repair place sort it out .thanks

 

[Figaro]

Try cleaning existing sensor, many recommend coke.
Having said that they never seem to work properly.
I never consider mine accurate, just brim it and I can estimate how long it'll last.

 

[Bren360]

Is the sensors inside the tank or outside the tank, im not sure were to get coke from, thanks for your fast response.

 

[Bren360]

I have just told my husband and he said coke a cola, is it like a can full?

 

[Bren360]

Thanks

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[Figaro]

I think most are a kind of float arrangement inside the tank.
Is it fresh or grey your having troubles with ?
If grey, some people recommend putting cheap coke down, driving to slosh it around then rinse out. Never tried it myself.

 

[Figaro]

A couple of 2 litre bottles I think, just the cheap Aldi stuff

 

[autorouter]

Can you see inside the tank? Can you access the top of the tank? There are many kinds of sensor, but the ones I've seen are either several vertical wire rods or two vertical wire rods.

It sounds like you have the type that has a stepped scale, maybe 0%, 25%, 50% 75%, 100%, which will be several vertical rods of different lengths. One for each step level, plus an extra one. Two long rods reach to near the bottom of the tank. When water bridges the rods, the circuit senses the change in resistance and registers that water is present. By measuring the resistance between each of the rods and one of the long rods, the circuit can sense which rods are in the water, and shows it on the display.

There is one wire from each of the rods to the circuit in the display panel. If there are bad connections, some of the sensors might not work. Or the wires could be shorted, another way to get a false reading. If there is dirt/gunge on the wire rod, the resistance might not be what is expected. So clean the wire rods and check the connections.

 

[tonyidle]

I think most are a kind of float arrangement inside the tank.

If only they were! Most comprise six stainless rods: 1 rod top to bottom, 1 rod almost top to bottom, three more rods from top to 3/4, 1/2, 1/4 , full. Each rod is connected to the common (longest) rod by the water content and indicates level via sensitive electronics using a meter, LCD display, or lights. In an alternative and equally common version the rods are replaced by a series of studs screwed the tank wall. In either case most faults are caused by the rods or studs being bridged by (normal) algae or other deposits. The rods can only be bridged at the top where they are mounted to a fitting so that's where cleaning should be concentrated and best achieved by removing the fitting and rods. For the stud type a tank cleaner or a bottle of Coca Cola will clean the tank walls.

As autorouter said

 

[Bren360]

I have no clue, its the fresh water that is reading 75% full. It looks like a big job, i will try the coke thing as the timberland place is over 100 miles away, looks like an expensive job,another secret the dealer never told me.

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[Bren360]

I cant see in the tank,

 

[Gellyneck]

I can understand your frustration with the gauges showing incorrect levels, we suffer the same along with a lot of others!
Yes, cleaning with cola (cheap and cheerful out of Lidl \ Aldi will do) could work however you'll probably have the problem return within a short period of time. You can also get "pukka" cleaners, eg Puraclean, but the issue just keeps returning. It's a cr*p design of the sensors that's the root cause.
You can get a different design that seems to work better and I think Diabalo may have self-fitted.
We've just given up however we measure the fresh water going in when we fill the tank so we know how much we've put in. Manual \ rough calculations from then on.
If it was me, I wouldn't worry yourself about it and live with it like loads of others.

 

[Diabalo]

I had the same problem and it drove me crackers tried all the cleaning remedies but the the problem soon returned, in the end I fitted Horst miracle probes a couple of years ago and the waste tank readings have been spot on ever since, and no cleaning needed at all. You can get them from TankBlankets but I got mine direct from the states at half the price. They are expensive but for me they worked.

TankBlanket.....Motorhome,Caravan, Leisure & Support Vehicle Tank Heaters : Winterisation thats works! - Horst Miracle Probes

New page

www.tankblanket.co.uk

 

[WillH]

I just ignore mine and fill/empty as required.

 

[Devon Sue]

You wouldn't clean a fresh water tank with cola surely?

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[M-J]

What make/model is your motorhome?

 

[Pausim]

You wouldn't clean a fresh water tank with cola surely?

I was thinking the same, cola for cleaning the grey water is ok but putting it in the fresh water tank is something I would avoid. Likely to gum up the water pump and taint the drinking water.

 

[SMB]

I think from memory previous posts mentioned white vinegar is used by some to treat the sensors in the fresh water tank. Keep meaning to try it as my sensors haven't worked properly for three or four years, tried using puriclean but that didn't help.

 

[Deneb]

I've only had the problem once. Cleaned the tank with Elsan Fresh Water Tank Cleaner two years ago and no problems since. The tank has the rod type sensors.

The waste tank has stud sensors in the sidewall. They will give false full readings if the outside of the tank is wet IME, e.g. after driving in the rain or condensation on the outside of the tank.

 

[Glas Robin]

Can you see inside the tank? Can you access the top of the tank? There are many kinds of sensor, but the ones I've seen are either several vertical wire rods or two vertical wire rods.
View attachment 354431

It sounds like you have the type that has a stepped scale, maybe 0%, 25%, 50% 75%, 100%, which will be several vertical rods of different lengths. One for each step level, plus an extra one. Two long rods reach to near the bottom of the tank. When water bridges the rods, the circuit senses the change in resistance and registers that water is present. By measuring the resistance between each of the rods and one of the long rods, the circuit can sense which rods are in the water, and shows it on the display.

There is one wire from each of the rods to the circuit in the display panel. If there are bad connections, some of the sensors might not work. Or the wires could be shorted, another way to get a false reading. If there is dirt/gunge on the wire rod, the resistance might not be what is expected. So clean the wire rods and check the connections.

Bren360. Autorouter has provided your most likely solution here.

It is almost certainly not a big nor a complicated job or one that warrants travelling 100 miles. Just open up the tank and look inside. if you have sensors like the above it should be easy to diagnose a problem and fix it. For example the 3/4 length and longest probe may be touching/shorting - hence reading 75% all time time.

If cleaning doesn't solve the problem, then replacement probes should be relatively cheap to buy and install.

I would hesitate personally before putting a lot of sticky coke in my fresh water tank - you'll need to rinse it very well through all the pipes and taps to avoid it gumming things up I would imagine. Fine for your grey water tank though.

Good luck and report back how you get on.

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[Glas Robin]

I cant see in the tank,

Why not? If you provide a few more details it will help people to help you.

Guessing here.... open one of the caps and use a torch?

 

[Pausim]

I don’t know about Bren360 ‘s Timberland but a lot of motorhomes are still built without accessible inspection caps on the tanks. Perhaps forgivable on a van conversion where they are maintaining the integrity of the floor pan but otherwise very shortsighted. This may make the cleaning of probes or float a bit more difficult.

 

[Deneb]

Honestly, Elsan Fresh Water Tank Cleaner worked for me, after trying various other methods, and saved me having to drop the tank to access the sender unit, which was in the top of the tank under the metal floor of a PVC.

 

[Jonno1103]

I agree with Deneb as a first response, try a concentrated dose of tank cleaner filling to 3/4 so it sloshes around on a drive.
If I remember correctly the fresh water tank is inboard under the sink unit next to the drawers. If so removing the drawers and fascia will give you access to the tank level probe allowing you to replace it or for removal to deep clean it- karcher type steam cleaners are good for this with the power contacts covered in duct tape.

Many motorhomes are still built using tanks without any twist cap access and the need to immerse your hand inside to pull the emptying bung and many PVC's are constructed with plastic coated maintenance free stainless steel tanks giving them less chance of furring and a longer life... but again the level probe is still the weak point in terms of build up.

Interestingly in the case of narrowboats they recommend replacing plastic tanks every three to five years or refitting with stainless steel.

 

[Jonno1103]

Perhaps forgivable on a van conversion where they are maintaining the integrity of the floor pan but otherwise very shortsighted.

I think it needs to be considered that many motorhome users may not have the mobility to to access their tank or even unscrew/tighten a removable lid. There are many accounts of owners suffering flooding due to loose caps and even new owners who haven't even bothered to check the lid is fitted correctly or tightened prior to first use then try to blame the dealer or coachbuilder.

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[Badknee]

Bren360 puritab works in the fresh water tank and cheap cola in the grey water tank.
We full time in our moho and use a ten ltr watering can to top up the fresh water and a fifteen ltr bucket to empty the grey tank.
Doing this I can check how much grey I get out so I know how much fresh to put in to replace it. Do this every couple of days or so and you will always have water.

 

[SMB]

Can you see inside the tank? Can you access the top of the tank? There are many kinds of sensor, but the ones I've seen are either several vertical wire rods or two vertical wire rods.
View attachment 354431

It sounds like you have the type that has a stepped scale, maybe 0%, 25%, 50% 75%, 100%, which will be several vertical rods of different lengths. One for each step level, plus an extra one. Two long rods reach to near the bottom of the tank. When water bridges the rods, the circuit senses the change in resistance and registers that water is present. By measuring the resistance between each of the rods and one of the long rods, the circuit can sense which rods are in the water, and shows it on the display.

There is one wire from each of the rods to the circuit in the display panel. If there are bad connections, some of the sensors might not work. Or the wires could be shorted, another way to get a false reading. If there is dirt/gunge on the wire rod, the resistance might not be what is expected. So clean the wire rods and check the connections.

I have accessed the water tank sensors which are similar to the ones shown in your picture and just scraped off the scale from them with my fingers after wetting them, took about ten minutes and the sensors are working fine now. Can't believe I left it so many years to try and sort out!