Holding tank monitors?

[JimM68]

My just bought 99 pace arrow has whet I believe is a conventional (not a 2 wire) ventline monitoring system, built into the range hood,

It has 2 rows of lights, each with empty, 1/1, 1/2, 3/4, and full, and a separate switch for each monitored item.

Best as I can tell / recall, everything works (I don't recall a reading other than full on the propane, will verify tomorrow, propane is known to be down to 1/4) (Batteries have never read anything but full, but as far as I know, they have always been fully charged.)
The fresh water level for sure does read correctly.

BOTH holding tanks only light the EMPTY light. I've for sure filled them at least half once.

Any info on how to test, troubleshoot, and repair this system is appreciated. I'm gonna bring the RV home tomorrow and work on it. What I typed above is from observations and what I've learned searching and reading here, I'm a newby and appreciate any/all help.

[tps0424]

Jim... As far as I can tell, the monitors are more of a guess than an actual reading. I've had trailers where the tanks were always empty no matter how much was in them and my present moho always has a 2/3 full black tank unless it makes it to full. After emptying it, it's back to 2/3.

Good luck.

[J Walker]

The holding tanks and fresh water tank without much doubt use the sensors which are just metal screws in the tank attached to a wire. When the level reaches the screw you have conductivity to ground and a light should go on. If it does not you have a wire removed from the screw. Most have the problem of indications of a higher level than is the case. That is due to residue inside the tank causing conductivity to ground. I have this situation in my black tank and various cleaning procedures take care of it. A sprayer inside the tank is the most effective. I don't know how the propane level is detected. The battery level is no doubt voltage.

[RV Wizard]

The batteries will always show full if you are plugged in or have the generator running. This is due to the fact that the charger is on line and to read a closer to actual is to have outside power off.
The lp sensor is part of the tank gage. Make sure it is connected at the tank gage.
The black tank usually can be deceptive as indicated in above post from residue (possibly tissue paper hanging on the sensor screw to ground (lower) screw. Cleaning will correct problem until next dump or so.
Bottom screw is the ground plane. as fluid (normally) build up in the tank to conduct to next sensor (screw) the corresponding light will illuminate. If not you could have an open conductor. Ohming out the wire will troubleshoot if it is the wire or a bad resistor pack located at the tank connecting all sensors to return conductor.

[Clay L]

A brief description of the way the most popular system works follows:

The sensors are just stainless steel screws going through the tank wall or in some cases blind well nuts are used - my friends Fleetwood Flair is done with well nuts.

If it's made by Ventline as many are, there is a 68k ohm resistor between the full and 2/3 sensor and one from the 2/3 sensor to the 1/3 sensor. The wire from the panel connects to the full sensor. On some units the resistors are potted in a small plastic cap close by the tank with one wire leading from it back to the panel. There is another wire from the ground sensor also going back to the panel.

On others all four wires go into the wiring harness and I don't know where the resistors are located. Maybe on the display panel?

The display panel has five "LM339 Low Power Low Offset Voltage Quad Comparator" ICs (one for each waste tank, one for the propane tank, the water tank and one for the battery voltage) that are used to sense the voltage drops across the sensors and activate the proper LED.

An empty reading could indicate an open circuit - top or bottom sensor lead - or a bad IC or other component. It seems odd that two ICs would go bad at the same time but not impossible.
I would first make sure all the connectors on the display board are tight and then go on from there.

[blacktie.shooter]

Quote:

Originally Posted by JimM68 BOTH holding tanks only light the EMPTY light. I've for sure filled them at least half once.

The holding tanks are where the gauges typically have a problem. Before you make any physical changes, make sure your problem is not just crud crusting on the sensors. As J Walker says, a sprayer on the end of a hose is the best route for the black tank.

In the grey tank, I've tried some of the "cleaners;" save your money. I read on one thread that after dumping, and rinsing or back-flushing, add a half gallon of white vinegar and some water, then let it slosh around some while driving. I gave it a shot and it seemed to work fairly well, not perfect, maybe, but now I add the vinegar every now and then. Overall, has been a help.

I know the propane gauge is supposed to read as a percent of the tank capacity, and your tank should never be more than 85% full. My gauge seems to read on the high side, for whatever reason. When it says a little over half, I can put twelve gallons in it, and it is only an eighteen gallon tank. Go figure. Good luck.

[JimM68]

Well, I've verified the propane is reading just fine. I've also found a schematic in "the book"

This is NOT the common ventline 2 wire system.

The 3 holding tanks (fresh, gray, and black) are served by 6 wires.
There are common 1/3, 2/3, and full wires, only 3, in parrallel to all 3 tanks.
There are 3 "trigger wires", one to each tank, activated (I assume) by the switches.

The fresh water (which works) works by lighting up all the lights to the current level, that is, when it is 2/3 full, the empty, 1/3, and 2/3 lights will all be lit.

The gray and black will work the same way. I'm now seeing some light on the 1/3 on the black tank.
I'm using some"biological" goop in the black tank, I'll use it in the rgay also, and keep using, and see if that helps. It does seem the system is working, except possibly for crud buildup in the tanks.

[Charles & Dawn]

Well mine have been not so good..I flushed my black tank 2 times in a 10 day campout until water was clear. Guess what it still showed a 1/3 full.

The grey tank does the same 1/3 full. the galley tank works fine.It's got to where I do not worry about them much.

[DAN L]

Quote:

Originally Posted by Charles & Dawn Well mine have been not so good..I flushed my black tank 2 times in a 10 day campout until water was clear. Guess what it still showed a 1/3 full. The grey tank does the same 1/3 full. the galley tank works fine.It's got to where I do not worry about them much.

i add a capful of liquid calgon water softener from wally world every time i drain the gray and black tanks. it keeps the sensors working ok.
when i first got my moho it was 5 yrs old and i used ice in the black tank while driving around to clean it.

[melvonnar]

The no fuss flushers you can buy at camper world work for me. keeps the sencers clean.

[wa8yxm]

Re: FLushers.. There is one that I SUSPECT might work and one that does. .The suspect is called "The RV Twister" and is a flush wand with a brass "Spinner" type nozzle

The one that does, (Well I built my own version) is by Valterra and I only know one store that carries it.. about 3 feet behind me as I type. It has what looks like a little fire nozzle on the end. (I don't really like the construction but then it may be good)

I made my own out of 1/2 inch PVC

You direct a hard stream of water at the sensor wall, moving it around to BLAST those suckers clean.. Works too.. At least my home made does, Since it's nearly identical to the Valterra unit (Just better made) I suspect it will work too.


On to testing the sensors.. You need a partner who can take direction and a jumper wire.. Automotive jumper cables can be used but the word "OVERKILL" comes to mind

The bottom sensor should be connected to ground, assuming there is at least 1/3 tank present jumper it to the chassis for a moment. Have partner push button and report "EMPTY"

Ok move chassis end of jumper to the TOP sensor, push button, Empty....

Ok, move bottom end of jumper back to chassis, Still empty? Broken wire or failed sensor board

Open sensor panel.. Identify the wire to the sensors and the ground wire,, Jumper them together, Still empty: Failed sensor borad.. FULL broken wire or bad connection.

IN my case they used a cap type wire connector, crimp on, to hook the very small (20 ga or smaller) wire from the panel to the larger (around 18 or 14 ga) wire they strung down to the tanks. The result was the smaller wire pulled right out of the connector.

Re-connected, (A bit of solder makes sure it's solid) and it worked great

[Roadfrog]

I had problems with mine too. Rather than fart around trying to troubleshoot for too long, I just replaced the sensors. You can get them at the RV shop of your choice for about 2 bucks apiece. took me about 25 mins to do all eight in both tanks. Grand sum of about 15 bucks and they now work as they should. All you do is loosen the screw of the sensor (they're called "well-nuts") and pull the rubber plug out, pop the new one in and tighten the screw. It's as simple as can be. Just make sure the tanks are empty! LOL

[melvonnar]

Quote:

Originally Posted by Roadfrog I had problems with mine too. Rather than fart around trying to troubleshoot for too long, I just replaced the sensors. You can get them at the RV shop of your choice for about 2 bucks apiece. took me about 25 mins to do all eight in both tanks. Grand sum of about 15 bucks and they now work as they should. All you do is loosen the screw of the sensor (they're called "well-nuts") and pull the rubber plug out, pop the new one in and tighten the screw. It's as simple as can be. Just make sure the tanks are empty! LOL

I didn't know that; you mean that screw in the middle of the sensor?
if thats it great; never tried taking that screw out.

[Roadfrog]

Quote:

Originally Posted by robert h I didn't know that; you mean that screw in the middle of the sensor? if thats it great; never tried taking that screw out.

Yes, there should be at least 4 on each tank. Simply unscrew it as much as you can and just pop off the sensor. The rubber grommet that the screw goes into has a small nut in it that is the sensor. Pop out the grommet with pliers or whatever and pop the new sensor/grommet in. When you tighten the screw, it swells the grommet to form a seal on the tank. Trust me, this is a simple job if you can get access to the sensors. Some tanks are hard to get at. Mine was not and it sounds like yours aren't either. You could even just clean teh sensor when you take it out and reinstall it if you prefer.