Sensor Panel Help Please

[Jim & Susan]

Just wondering if either of you ever figured out the problem. Interesting thread.

I'll have to check tonight, but I'm pretty sure that my '73 has a power and ground directly off the Univolt.

Jim

[BillTex]

Stay tuned...lengthy thread detailing the resolution on it's way!

Bill

[DKDarrow]

Hey Folks.........just got back from 2 weeks of video editing/relaxin/rest..........
Early in this thread I talked about putting a few drops of WD-40 on the adjuster screw for each switch/rheostat and then working the screw in and out a few times............No results I thought.......A few days later the grey water began to register 1/2 full, when full and the black was 3/4 when full................These had not worked for 2 seasons...........

A few days later decided to fill up the fresh water tank as the grey and black were both full again.....................IT WAS WORKING.........

Pulled the panel apart again...........a few more drops of WD 40 on each screw, let set overnight and am able to get a full reading on each..........Calibrated them and YES they are working..........

God is so very good to me.................Dennis

[Jim & Susan]

Congrats Dennis. Bill, looking forward to your thread.

Jim

[BillTex]

Yes, I also tried Dennis' fix last week, but it was clear my gauge failure was of a different nature...
I believe I made a break through last night and will document the entire fix and post in a week or so...

Bill

[BillTex]

This post details the process to repair to my once working monitor panel; let me define what happened. As we have been doing an increasing amount of boon docking, the ability to monitor fresh, particularly, becomes critical. If you camp with hookups, you can easily get by with out gauges.
If your failure mode is similar,and your system is of the same vintage (80’s-90’s) you may benefit from this troubleshooting and repair process.
The system uses a board manufactured by Larson Electronics ; board should be labeled on the back, which utilizes foil pads on the tanks. From what I have found, this system was used by AS in the 1980’s until about mid 90’s. A voltage is passed to the tanks, and based on the amount of fluid in the tanks contacting the foil pads (resistance) a voltage is returned to the gauge panel, resulting in a certain number of LED’s illuminating indicating the fluid level in your tank (s).

Failure mode, in our case, was catastrophic; one day all gauges were working, the next day all three tanks (Fresh-Black-Grey) would only return a reading of “E.” All other functions controlled by the monitor panel (fan/light/battery level) continued to function. The manual outlines several causes for gauge readings of “E”; lost connection at foil pads on tank, bad board, and bad wire, lost ground, etc. It is my understanding that several other Folks have had this exact same failure, so this may be a very typical failure mode.
Some of these conditions would be easy to diagnose; I had ground, it was unlikely the foil on all 3 tanks came loose at the same time (camper had not moved since this happened). After checking all the obvious, I began to dig deeper and started to think that it was the board that failed. I pulled the board and diagnosed at board level. I found one proprietary chip that I began to think was faulty. AS said they no longer stocked this board or any components. Then I tried to contact Larson, which has since been sold/bought 3 times. No one there had any real history with this board, it is no longer manufactured, and there was no willingness to diagnose. I then contacted a Tech house which offered to diagnose and rebuild the board at some cost. They did infer that it would be more cost effective to gather several boards to send in for repair. I contacted some other members and started to consider doing this. After some time passed, I contacted the Tech house again and they said their business was ramping up and they sounded a little reluctant to take on this project (understandable). Meanwhile I have been scouring every Salvage yard, internet site, other members looking for another board. One year later, I hear from a member that (most unfortunately) has a tree fall on their early 90’s AS and is parting out. They say their monitor panel was working fine, and yes it is a Larson. One paypal and a few days later my new board arrives (still winter here in New England); I rush outside and plug in the board-Eureka!? Nope, same failure mode, tanks only read “E.” Disheartened, but not discouraged, I reassess my attack; it must be in the harness.
The next step is to begin working through the harness at the board connection, using the schematic in my manual it soon becomes clear that the problem is in the blue wire (fresh) red side (positive return from tank) which supplies power to all 3 tanks! As the only exposed wire is maybe 12” or so at the board and under the range hood, and the bulk of it runs inside the wall, that left only what is in the belly of the beast. Now what? Drop the pan? (This as you know is a big project; jack up, support, drop the pan, fix it, reassemble). I call AS again and they say there should be access through the wardrobe near the water pump…well…maybe a 6” hole, but it is not enough to see anything. I also asked if there were any common connection for the tanks in the belly and they reply that no, all 3 tanks are wired independently. This does not make sense to me as all 3 tank gauges failed at once and I am sure they share some common connection. I start to poke around underneath and soon find myself near the dump valve. I pull away some silicone sealant and look inside with a flashlight…what is that? The blue wire? Can’t be I am on the opposite side-why would the wires run all the way over here. I reach in and grab the wire; there is sufficient slack to pull it out through the small hole I exposed adjacent to the dump valve.



What do I find? A severely corroded harness with the same 12 leads that are found at the board. After snipping off the end and stripping back the insulation, I bypass the tank and yes! We have return voltage! So I mark off all 12 wires (so as not to get confused between voltage out and return) purchase some high quality butt connectors and liquid electrical tape (this is not a job you want to repeat often) and wire everything back together. Be sure to follow the schematic; blue wire red insulation to blue wire red insulation, clear to clear, etc. It took an entire year, but now I have my gauges back and Life is Good!
Summary; if you have this system, and you have had this failure mode (sudden failure of tank (s) gauges, no reading, or only “E”) then this repair may be worth your time. Maybe I got lucky, but I would start by peeking around the dump valve/pipe and look inside for the blue wire and associated harness. Maybe you can have working gauges again too! If anyone has any questions or needs more details, please contact me.
Bill

[DKDarrow]

Bill...........You are a TRUE HERO............ONE OF A KIND.........GOD BLESS YOU.........Dennis

[kontiki]

I have an 1989 Excella. The control panel has a switch labelled "Auto-Fill", I cannot find any info in the manual that refers to this. Does anyone else have this on their control panel? If you do what does it do.
Jim

[BillTex]

Dennis, I thought you would like this one...

konticki, that activates a valve to fill your fresh tank when hooked to city water.

Bill

[DKDarrow]

Love those little mysterys and then the answer out of the blue........What would be funny is when the switch is left on and then wondering how that durn tank kept getting full............

[BillTex]

Hey Dennis-how are your gauges holding up?
Did you calibrate?
I am so thrilled to have working gauges, I find myself going out to the backyard just to light them up!

Bill

[DKDarrow]

Hey Bill.........

I really relate about checking the guages and the feedback that it gives your spirit............

Since our return from the "trail" to here at home/farm so many chores to get caught up on before we head out again...............Have had to move the AS in and out of the barn 3 times to work around other equipment, wash it, wax it and such...........

Now it is perfectly level and one of my missions today or tomorrow is to fill each tank, adjust each rheostat screw to where it just lights up, and then empty it to see if it registers empty correctly.........Right now my black tank registers 1/4 even though it has maybe a couple of gallons in it.........

Keep on goin Bud and remember you have a very level spot with power to spend however long you want here in N. Ga..........God Bless........Dennis

[BillTex]

Thanks Bud-we are finally all cleaned up and ready to go...wish it woud warm up a bit.
Cloudy and cold...again...in New England. Wish we could offer Brian (moosetags) better weather. He is up North boppin around...

Oh well-beats work!

Bill

[Skatiero]

Bill, thanks for the very thorough Feedback!

[BillTex]

skatiero...you are welcome.

That thread was a blast from the past!

Happy to report gauges still work...

Later, Bill

[Skatiero]

That's a great update, Bill!

[AtomicNo13]

I have several of the Texas Instruments ICs as well as all the transistors gratis to anyone who needs them. The ic's are longtime unobtanium but the transistors are fairly common. I suggest you solder in sockets for the ic's first.....

Regarding the autofill...
I suggest while using you remove the exterior fill cap to avoid popping off the tank breather line. You can fill at a greater rate than the air can escape via the hose. Popping it off can lead to a wet belly!

[frone]

Enjoyed reading the posts -- they have helped me alot.

We have a 1993 AS that I purchased a month ago. OK shape and working through the systems. Tank level indicator does not work and I have determined that it is the little test switch on the front panel and I need a new one. By shorting the switch I get some readings, switch does nothing -- passes no current and is always open.

Can anyone help me with a source for a new "test" switch? Thanks