- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
HOW please ???? - 2001 Mercedes Hymer B680, TIA
Replacement of black water tank LEVEL SENSOR
- Thread starter bigalw35
- Start date
- Nov 3, 2013
- 3,315
- 10,545
- Funster No
- 28,868
- MH
- Fiat Ducato Auto Wildax
- Exp
- C/van since '73 .M/h.2009
Hi.
Being as you have had no replies. Our 100 ltr Waste water tanks gauge is not working.( To sort it means dropping the tank,stripping insulation etc ) So when we empty it ,i fill the Fresh water 100ltr tank up to the brim ( gauge works ),when that one is empty the other one must be near full. Simple ? Works for me.
You will have allready thought of this,but i am not taking the mickey. Genuine reply.
Tea Bag
Being as you have had no replies. Our 100 ltr Waste water tanks gauge is not working.( To sort it means dropping the tank,stripping insulation etc ) So when we empty it ,i fill the Fresh water 100ltr tank up to the brim ( gauge works ),when that one is empty the other one must be near full. Simple ? Works for me.
You will have allready thought of this,but i am not taking the mickey. Genuine reply.
Tea Bag
Our waste water tank rarely gives accurate readings. When empty it can read 100% at other times 50%. I assume that a good clean with water or chemicals should rectify this but how to do this?
One reading last week was - - -. Doing large mileage just now touring S Spain so sloshing about should help?
One reading last week was - - -. Doing large mileage just now touring S Spain so sloshing about should help?
Are you sure it has a Black tank - for toilet? I would have though a Cassette would be more likely
Shrimp
Funster
Title says Black tank but post is on about waste water tank!
Our grey water tank never reads correctly, the probes that give the reading get mucky then stop working, there should be a plate somewhere-in van-to access the tank!
Our grey water tank never reads correctly, the probes that give the reading get mucky then stop working, there should be a plate somewhere-in van-to access the tank!
Subscribers do not see these advertisements
- May 8, 2011
- 4,261
- 55,434
- Funster No
- 16,317
- MH
- IH Tio 630 RL
- Exp
- Since April 1846 but have always camped.
Ours has never worked for the last 7 years. Just leave the tap open with a bucket underneath.
On my 2004 B544 I replaced the waste water sensor unit by removing the tank access screwed top, and then unscrewing the internal sensor unit plastic locking nut. I found the main 'failure' with the unit was due to.the poor internal electrical/mechanical connections between the top of the probes and the output leads inside the potted section.
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
We have a separate black tank and a separate cassette, I put Solbio in the tank, a drive around I empty the tank, but it still shows as being full
Edit
I get confused with the grey tank and the black. The tank I’m having problems with is the tank underneath, where all the sink’s, shower wast goes
Last edited:
My fresh water tank was a white coloured one and my waste (sink, shower) tank was a black coloured one!
Last edited:
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
So, many thanks for the replies so far 
but back to my original question, how do I get to the sensor in the tank underneath ?
but back to my original question, how do I get to the sensor in the tank underneath ?Subscribers do not see these advertisements
What sort of sensor? The most common type uses the liquid in the tank to connect varying length rods to a common rod. The rods can be replaced by a series of screws into the side of the tank. The rod variety can only be accessed through the large cap whether it be in the bottom of the tank, or top, or both. So it's difficult to know how to answer your question without much more information about which tank specifically (grey waste or black toilet waste), is it insulated, and which types of sensor.
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
That’s the same as mine, there’s various little trap covers, but I can’t find one for the waste tank sensor
Access to my tank and sensor unit was via an internal small floor trap cover immediately above the tank.
I think 'my' sensor is a common one for 2000/2005 Hymers and is just one unit of probes/cable/connector attached to the tank with an internal 32mm plastic nut.
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
Many thanks SS, I imagine that would be in the garage on the “top shelf” looking in from the door ?
Last edited:
On my Autotrail the sensors are just stainless screws set in the side of the waste tank at the various levels, I replaced them with Horst miracle probes and the readings have been ok ever since.
Subscribers do not see these advertisements
Have you done a 'Search' for any previous postings from any other B680 members?
- Aug 18, 2011
- 12,484
- 18,873
- Funster No
- 17,808
- MH
- AUTOSLEEPER SYMBOL
- Exp
- since 2007.Tugger before since 1970
Same here,,,I work on the theory that if I need to top fresh water tank up ,which I try to do every day ,I therefore need to empty grey waste as it's a smaller tank..Gauge has never worked on freshwater tank and there isn't one on the grey.BUSBY.
Its not the colour of the tank itself, its the classification of the waste, From the shower basins and sinks are called Grey Water and waster from the toilet is called black water. I think you re struggling with the grey waste, those tanks usually have either a spinoff cover or a screwed in probe, you need to get to the probe and get the limescale off it. I would expect the grey tank to be in the double floor somewhere so you need to find the hatch, if its not in the floor ( Earlier Mercedes based models only have a partial double floor) so it could be hanging underneath somewhere.
Wherever it is it will be low down
I believe the op has already acknowledged it is the grey water tanks sensors that need attention. Has any Hymer 680 owner found access to service the sensors?
Subscribers do not see these advertisements
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
Hi and many thanks for your input, unfortunately I tried that little panel but that only hides one of the waste traps to the shower, I also think that our tank is a little further back, towards the rear end
Last edited:
And a hole in the bucket
- May 8, 2011
- 4,261
- 55,434
- Funster No
- 16,317
- MH
- IH Tio 630 RL
- Exp
- Since April 1846 but have always camped.
I didn’t mention that.
My B544 waste tank was located the 'short' distance between the shower and sink.
A Hymer manual download for a 2010 (?) B680, shows both the waste water and fresh water tanks side by side under the same floor trap.
Happy hunting!
Subscribers do not see these advertisements
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
Ours is a 2001 b680, the fresh water tank is under the rear of the mid dining area seat/table and I changed the sensor in that tank a couple of years ago, perfect, following the earlier post concerning the alternative sensors, im just about to order a set of four, I’ll keep the site informed
OP
OP
- Oct 13, 2016
- 1,068
- 903
- Funster No
- 45,568
- MH
- Mercedes Hymer B680
- Exp
- Been moho’ing for a time now
Many, many thanks for the replies, but I'm going to try the horst miracle setup, it would appear to be a better setup, BUT, does anyone have the wiring diagram/colours of the existing waste tank sensor please 
or the whole wiring diagram mainly what I need is the colour for the common probe
or the whole wiring diagram mainly what I need is the colour for the common probe
As I have an Auto-Trail mine was a direct replacement so I had no probs with the wiring. If yours is the top fitting with probes using a multimeter you should be able to determine which prob is connected to which wire. Hopefully someone will be along with the wiring diagram.Many, many thanks for the replies, but I'm going to try the horst miracle setup, it would appear to be a better setup, BUT, does anyone have the wiring diagram/colours of the existing waste tank sensor please
Ive got the Horst sensors, grey and black, my tanks were wired for that kind of sensor so I drilled new holes and fitted them easily, they were great at first but still need cleaning from time to time.Many, many thanks for the replies, but I'm going to try the horst miracle setup, it would appear to be a better setup, BUT, does anyone have the wiring diagram/colours of the existing waste tank sensor please
If you've found the grey tank and can get at the prongs a good clean will probably give you years more service. There will almost certainly be a hatch.
Join us or log in to post a reply.
To join in you must be a member of MotorhomeFun
Join MotorhomeFun
Join us, it quick and easy!
Log in
Already a member? Log in here.