Fresh Water Tank Sensor Help

Nathan48035 · 08-07-2020, 02:39 PM

Wondering if anyone has an idea what could be going on with my fresh water tank level sensor.

It reads empty, 1/3, 2/3 just fine, but doesn't read full. I tried replacing the resistor pack thinking it was either the resistors or maybe one of the connections, but it still is not working.

I've had the camper for 8 years and it's always read full in the past so I'm pretty positive it's not an issue of the tank not actually being full due to water siphoning out or something like that.

My understanding is that the actual sensor part that goes into the tank is pretty much just a metal stud so I wouldn't think that would be bad, but now I'm wondering if maybe that is bad. I do have real rusty water so it could have lots of deposits on it. Not sure if that would cause this though.

I don't think the control board is bad since the other tanks all show full when full.

Does anyone know if you can replace the actual sensor studs without tanking the tank down?

**norty1** · 08-07-2020, 03:26 PM

Horst probes can be installed and the wires moved over. There are threads on JOF and on You tube.

https://www.googleadservices.com/pag...BAgKEAo&adurl=

JimD · 08-07-2020, 03:48 PM

Burnt out LED indicator? Break in wire from tank to panel?

Quick check - go to tank sensors and swap the full sensor and 2/3 (or 1/3) wire positions and see if the light comes on. If the light comes on and the sensor you swapped with goes off, there is an open in the wire somewhere.

If you don't feel like swapping wires you could just jumper the full tank sensor with the 2/3 sensor. I believe these sensors just sense the resistance of the water between the bottom tank sensor and the 1/3, 2/3, full sensors. As you say, they are probably just studs through the tank.

A simple light circuit would be 12 volts, an LED, a resistor (probably), the full tank probe, and the bottom tank probe. The bottom probe may be at ground potential which would then supply the ground to the LED to complete the circuit. When the water completes the circuit between the 2 probes the LED should light up. I am guessing there is a resistor in the circuit to add to the resistance of the water. In any case I would not jumper from the bottom sensor to the full one because that may cause an over current to the LED.

Nathan48035 · 08-07-2020, 06:15 PM

I've seen those Horst probes and heard they were better. If I knew these sensors were my problem I would have no problem buying some of those. I'm just not sure it's the sensor. I did check out the videos and the sensors seem fairly easy to remove with the tank in place so that is a big bonus.

It's not a problem with the LED for sure, because the black and grey use the same LED set and the full works on those tanks.

Instead of swapping the sensor wires I just took the wire off of the full sensor and added it to the 2/3 sensor (so I had both 2/3 and full wires hooked up to 2/3 sensor). It was still the same result (empty, 1/3, 2/3 lights on, but not full light).

I'm really stumped. I know it seems like an open, but the open would have to be in the resistor pack wiring and I just replaced that all. From the resistor pack to the control panel is just 2 wires (ground and positive) and those must be working as the bottom 3 sensors seem to be working correctly.

It also doesn't seem likely to be the control panel circuit because I would think that would use the same circuit for each tank (just depending on what button is pressed) and for the other tanks the full LED works.

Any other thoughts?

**JFlightRisk** · 08-07-2020, 06:41 PM

I just replaced my gray tank sensors with the Horst's. If your wires are the same configuration, they should be (top sensor, down) red, green, and yellow and white at the same level on the bottom. With a 2 1/2 or 3' length of wire, if you touch the white to the red, the monitor panel should read full. If it does, the sensor's fine, and it's a connection or lead issue. Note: The sensor is only two pieces. The rubber grommet, and the stainless steel stud, which is all one piece that the nuts thread onto. The nuts on the other hand, aren't stainless, and they will rust.

The Horst Miracle Sensors are great, but designed for gray and black tanks. I suppose the gray tank version could be used for a fresh water tank, but I don't know anyone that's done that.

Nathan48035 · 08-07-2020, 06:50 PM

JFlightRisk, you bring up a good point. The nuts do rust. For my latest check of moving the full wire down and adding it to the 2/3 sensor. I just put on the back of the 2/3 stuf after the nut that was already there holding on the appropriate wire. In other words that wire ring was sandwiched between the 2 nuts. It may not have been making good contact. I will have to try that again and move that wire down to the base next to the actual 2/3 wire.

**JFlightRisk** · 08-07-2020, 09:21 PM

A helper checking the monitor while you're underneath allows you to make a better connection on the studs. I had the DW do that after I swapped the sensors. That's how I found out the "full" and "2/3" wires were wired wrong from the factory. I grounded the 2/3 sensor, and she said "FULL!" That's why I remember the wire colors on them.

Let us know how you progress.

Nathan48035 · 08-08-2020, 05:46 AM

Good thinking. I'll get some up top holding the button down as I'm playing around down there to see exactly what is going on.

Nathan48035 · 08-10-2020, 07:04 PM

I finally got back out there tonight and tested it again with the full wire pressed up against the 2/3 wire (no nut in between) and the full LED lit up. It seems like the full sensor must be bad. I suspect the part of the sensor in the tank is probably fine, it's probably the part on the outside of the tank where the wire gets pressed up against. I'm guessing there is just too much oxidation there and it's not making a good connection. I tried to hit it with some sand paper and file to clean it up, but didn't have any luck with that. It's in an awkward spot to get to and so I'm guessing I just didn't do a good enough job. I'm also guessing once I pull that sensor out I won't get it to reseal in there unless I replace it.

I'm leaving this Friday for a week long trip so I think I'm going to wait until I get back and then try replacing the sensor. At least the problem is narrowed down and making some sense now.

billcf7 · 08-12-2020, 09:46 AM

Install these and your tank level problems will be solved
https://www.rvupgradestore.com/RV-Ta...stem-s/164.htm

https://www.garnetinstruments.com/rv...38366699218750

Jagiven · 08-12-2020, 10:35 AM

Quote:

Originally Posted by Nathan48035

Wondering if anyone has an idea what could be going on with my fresh water tank level sensor.

It reads empty, 1/3, 2/3 just fine, but doesn't read full. I tried replacing the resistor pack thinking it was either the resistors or maybe one of the connections, but it still is not working.

I've had the camper for 8 years and it's always read full in the past so I'm pretty positive it's not an issue of the tank not actually being full due to water siphoning out or something like that.

My understanding is that the actual sensor part that goes into the tank is pretty much just a metal stud so I wouldn't think that would be bad, but now I'm wondering if maybe that is bad. I do have real rusty water so it could have lots of deposits on it. Not sure if that would cause this though.

I don't think the control board is bad since the other tanks all show full when full.

Does anyone know if you can replace the actual sensor studs without tanking the tank down?

What do you have for a camper? Do you have an open underbelly?

With what you have done, and if you have an open underbelly, I would suspect you have a broken wire or a corroded connection at the probe. again if you have an open underbelly, check the wiring under the TT. When I bought my TT, my wires were a mess and hanging down low. I pulled them up so road debris would have less of a chance to snap a wire. I also applied liquid electrical tape, to the connections to try to keep them from having corrosion issues. If you have an enclosed underbelly, those issues noted above are less likely, and you could have a broken wire somewhere in the system, which would be a lot harder to trace.

**JFlightRisk** · 08-12-2020, 12:20 PM

Quote:

Originally Posted by Nathan48035

I finally got back out there tonight and tested it again with the full wire pressed up against the 2/3 wire (no nut in between) and the full LED lit up. It seems like the full sensor must be bad. I suspect the part of the sensor in the tank is probably fine, it's probably the part on the outside of the tank where the wire gets pressed up against. I'm guessing there is just too much oxidation there and it's not making a good connection. I tried to hit it with some sand paper and file to clean it up, but didn't have any luck with that. It's in an awkward spot to get to and so I'm guessing I just didn't do a good enough job. I'm also guessing once I pull that sensor out I won't get it to reseal in there unless I replace it.

I'm leaving this Friday for a week long trip so I think I'm going to wait until I get back and then try replacing the sensor. At least the problem is narrowed down and making some sense now.

Yes, removing the full sensor will render it unusable. The metal part of it resembles a screw, with just a smooth head on the inside, and the threads to hook the wires to. The rubber that seals it will be distorted beyond useable again.

With a separate piece of any kind of wire, touch one end to the sensor with the white wire, and the other end to the "full" sensor while your helper tests the monitor panel. If it reads full, the sensor is ok. If you do decide to take it out, just have a new one ready to take its place.

Nathan48035 · 08-13-2020, 06:05 PM

Quote:

Originally Posted by billcf7

Install these and your tank level problems will be solved
https://www.rvupgradestore.com/RV-Ta...stem-s/164.htm

https://www.garnetinstruments.com/rv...38366699218750

I've seen these before. I will be thinking about them for my next trailer for sure. I don't want to spend the money on this one though. I have been planning on upgrading for the last couple summers. If it were not for the whole Covid 19 thing going on this summer, I probably would have upgraded this summer. It's hard to justify buying a new trailer though when you are reduced pay (when you don't really need one). There's always next year though.

Nathan48035 · 08-13-2020, 06:11 PM

Quote:

Originally Posted by billcf7

Install these and your tank level problems will be solved
https://www.rvupgradestore.com/RV-Ta...stem-s/164.htm

https://www.garnetinstruments.com/rv...38366699218750

Quote:

Originally Posted by Jagiven

What do you have for a camper? Do you have an open underbelly?

With what you have done, and if you have an open underbelly, I would suspect you have a broken wire or a corroded connection at the probe. again if you have an open underbelly, check the wiring under the TT. When I bought my TT, my wires were a mess and hanging down low. I pulled them up so road debris would have less of a chance to snap a wire. I also applied liquid electrical tape, to the connections to try to keep them from having corrosion issues. If you have an enclosed underbelly, those issues noted above are less likely, and you could have a broken wire somewhere in the system, which would be a lot harder to trace.

I have a X18D (hybrid) and it does have an open underbelly. I actually really like the open underbelly as the camper is getting older. It seems like it would be a real pain the rear to take the big tray down every time I need to troubleshoot something.

I think you are right though that the problem is due to corrosion. The wires should be good though. I bought a new resistor pigtail. That includes all the wiring going to each sensor. I think the issue is the corrosion on the sensor stud where the wire connects. I'm guessing its just not making a good connection there, but it's not the easiest to clean that up with the sensor in place.

Nathan48035 · 08-13-2020, 06:17 PM

Quote:

Originally Posted by JFlightRisk

Yes, removing the full sensor will render it unusable. The metal part of it resembles a screw, with just a smooth head on the inside, and the threads to hook the wires to. The rubber that seals it will be distorted beyond useable again.

With a separate piece of any kind of wire, touch one end to the sensor with the white wire, and the other end to the "full" sensor while your helper tests the monitor panel. If it reads full, the sensor is ok. If you do decide to take it out, just have a new one ready to take its place.

Thanks good to know that the sensor is a gone once I pull it out. That's what I suspected, but wasn't sure.

I think I pretty much did this test when I took the full sensor wire and pushed it up against the 2/3 sensor. It lit the full LED up in the camper. Seems like the wiring and all is good.

It is looking like my camping plans for this coming week are getting cancelled (was supposed to leave tomorrow) so I think I'll try and hit up the RV shop this weekend to grab a new sensor and give it a shot.

Nathan48035 · 08-28-2020, 06:09 PM

Finally got a replacement sensor installed. I had a heck of time getting the old sensor out of there, but finally got it removed. With new sensor in place the tank will now read full again!

I don't know if it was part of the problem or not, but the old sensor definitely had a good layer of rust on it. I fill my fresh with my untreated well water and it definitely has lots of iron in it. I need to run a line with softened / filtered water to one of my outdoor spigots.

Nathan

billcf7 · 08-28-2020, 08:39 PM

Eventually the new one will look like the old again

**JFlightRisk** · 08-28-2020, 09:13 PM

Appreciate the pic of the bad one. I agree the well water did that to it, but wonder if the other three are going to do the same thing, being originals.

billcf7 · 08-28-2020, 11:28 PM

Save the aggravation and go with SeaLevel tank monitors. You will wonder why you waited so long
https://www.garnetinstruments.com/rv-shop/

Nathan48035 · 08-29-2020, 06:00 AM

Yea, I assume the other ones will eventually have the same issue. That's not the end of the world though. I'm planning on upgrading the camper in the next year (give or take) so I'll wait and see what happens. If the other ones break I'll just swap them out too. The sensor was cheap and the rest will be easy to access so it's not a big deal at least. This top one was behind the angle iron that the tank sits on so it was a bit of pain to get to.

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