Community Forums

Kahoona · 07-20-2020, 01:30 PM

Hi
We have a National Tropical 33.5 with a 100 gal fresh tank. The level lights worked until recently when the 1/2 and 2/3 lights went out. In the picture the tank is 3/4 full but only the bottom light is on. The Top does work if it full.

My understanding, from threads I read here, is that the logic is cumulative: If one sensor is covered then it reads 1/3, if 2 are covered it reads 1/2, 3 covered is 2/3 and 4 is full. In that case having the top and bottom working means a bad board/led problem?

If that is true then do I need to replace the board and no point in dismantling the wet bay to check wires?

Does anyone know and if true then does anyone know more about this board and where to get one? Those numbers aren't getting me any info.

happy2rv · 07-21-2020, 06:56 PM

These work by probes sticking into the tank forming an electric circuit. There is a "common" probe at the bottom of the tank and then probes for 1/4, 1/2, 3/4, and full. The wiring harness has a different resistor for each probe and when you push the button to read the tank level, a voltage is sent through the wiring harness through yet another resistor. If water is covering the probe, it "completes" the circuit for the wire attached to that probe.

The resistor at the panel and the resistors on each probe, along with the resistance of the water itself, form a voltage divider network. The voltage at the junction between the wiring harness and the resistor at the panel will indicate which probes are in water completing the circuit.

Having said all that, the "electronics" of the control panel are rarely the problem. With these panels, the problem is almost always the probes in the tank. While it is possible that you could have a broken wire or a problem with the panel, it is far more likely to be a problem with probes.

Some of the probes are easily removable. They are basically a rubber stopper with a nut that spreads the stopper as its tightened. You loosen the nut and pull the probe out. However, some of them aren't so easily removed. These monitors are notorious for having problems, but it is usually the black tank that has the most problems.

There are alternative systems like the SeeLevel that use a capacative strip stuck to the outside of the tank to read the levels. Since these are completely outside the tank, they don't "foul" like the OEM tank readers. They also offer the benefit of true analog readings of percentage full instead of just 4 levels. They are pricey though and would require rewiring.

Kahoona · 07-22-2020, 11:08 AM

Thank you. You have answered my question nicely. I have a couple of other important things broken but when they are taken care of I will have to find the probes which are probably behind the wet bay and check connections and perhaps switch wires between the fresh and grey or jump wires to narrow the source down. We did have some mice that climbed aboard and got into the basement one day last month. They were removed right away but from what you say they could have gnawed a wire or two. Soon as I can get there I will post back.

Kahoona · 01-18-2021, 02:34 PM

Hi
hope that you left the thread followed while i was working on other more critical things. If anyone is here I found the sensors which were under a panel on the other side if the RV from the wet bay side. It was held on by hidden screws (rusted solid of course.) Here is what I found when I did testing. There are 4 sensors. There are empty, 1/2, 2/3 and full. Empty is always lit. Full will light as well as empty when the bottom is connected to full sensor. The 1/3 and 2/3 never light. The 1/3 and 2/3 should light when full is lit.

There is a something I did not expect. The 4 wires from the sensors go to a rubber tube fulled with RTV. 2 wires come out of the other end and head on up towards the panel. They cannot be traced because of the mess.

I cant figure out what is going on. Could it be a bad board? I believe 2 wires are intact or the empty and full would not work. Could it be the RTV filled tube? I could probably fit a sight glass between the fill hose and the drain. Kind of Steampunk. I am not prepared to replace the system with strips or anything.

HarryStone · 01-18-2021, 06:40 PM

Grab your meter, and a long wire. attach your wire with an alligator clip or like it to one end of the wire you want to test, then attach the other end to your test lead. Attach the other test lead to the other end of the wire and check continuity.

Kahoona · 01-19-2021, 08:09 AM

Quote:

Originally Posted by HarryStone

Grab your meter, and a long wire. attach your wire with an alligator clip or like it to one end of the wire you want to test, then attach the other end to your test lead. Attach the other test lead to the other end of the wire and check continuity.

I will do that today. The only part that I can test is the two wires from the connector near the tank to the board on the control panel. Unfortunately the 4 sensors to not connect to the board but they go to that piece of tube with RTV inside it where they become 2 wires. I posted a picture of that tube. Very strange.

Kahoona · 01-19-2021, 09:00 AM

Quote:

Originally Posted by HarryStone

Grab your meter, and a long wire. attach your wire with an alligator clip or like it to one end of the wire you want to test, then attach the other end to your test lead. Attach the other test lead to the other end of the wire and check continuity.

OK. Done. I do have continuity on the 2 wires going from the connector after the strange tube (see photo) and the panel. The problem has to be either in the board or in that tube with the rtv in it where the 3 sensors turn into one wire. I would try buying parts if I could find out where they come from.

Kahoona · 01-19-2021, 09:55 AM

I found a diagram of another system that identifies the tube as a Resistor Pigtail. Now to find how to test mine.

Kahoona · 01-19-2021, 10:31 AM

Found a resistance pigtail from the same mfg, JRV that may, if lucky, have the same values. Ordered from eBay. Relatively cheap way to find if it is the board or the pigtail.

HarryStone · 01-20-2021, 09:51 PM

Kib states:

K101 pigtail test procedure

the k101 pigtail can be tested with an ohm meter as follows

red to orange – 0 ohms
red to green – 68k ohms
red to yellow – 188k ohms

note: Do not short fresh water tank probes with jumper
wires. Water test or use a 43k ohm resistor for testing

HarryStone · 01-20-2021, 09:53 PM

https://www.forestriverforums.com/fo...es-131266.html

Kahoona · 01-21-2021, 06:59 AM

Quote:

Originally Posted by HarryStone

Kib states:

K101 pigtail test procedure

the k101 pigtail can be tested with an ohm meter as follows

red to orange – 0 ohms
red to green – 68k ohms
red to yellow – 188k ohms

note: Do not short fresh water tank probes with jumper
wires. Water test or use a 43k ohm resistor for testing

Thank you for this info. It will make things easier to check.

Kahoona · 01-21-2021, 08:01 AM

How do folks clean the fresh tank to remove scale? I could see using vinegar but it would take 70gal of the stuff and then at least three fill and dumps.

Dav L · 01-22-2021, 07:54 AM

Clean the tank: If all other "normal" measures fail, then put a flush adapter on the tank outlet. Drill a hole on the top side. Insert a "Jetter" power wash hose and end into the hole and snake it into the tank. Keep the flush adapter's flush opened to a container / septic drain. Power wash the heck out of the insides.

Nasty job but it will clean out whatever is electrically messing with the interior of the sensors.