R31 Tecma head false full reading

[georgeboarhunter]

I am 2 weeks into the loop on 2023 R31CB. Main head gives red "full" light after one day out. Did the reset several times. Tank nearly empty, viewing rank with bright light shows no debris. Changed to green for 6 days. Now reading full again. Pumped out yesterday. No debris. Cut one wire to high sensor. Reset. No change. Cut second wire to sensor, reset, no change. Joined the two wires essentially jumping past the sensor, reset, no change. I can only do emergency flush. How can I fix this for the months ahead on this voyage?

 

[georgeboarhunter]

No one else having this problem?
I called Thetford yesterday. Sadly, they have eliminated ALL human technical support and all I got was a useless AI chat bot and zero assistance. Hoping someone here can offer an idea. Thanks.

 

[OverTime]

Sounds like an intermittant short?

 

[OlygirlNav]

We have had similar issue. One area to check is make sure there is no tape holding the sensors in place. The tape causes false readings. The other thing I did was added a squirt of dawn dish soap, then filled the tank with clean water and pumped out. It took doing this twice to get the green indicator. I listened for when the tank was getting full similar sound to when the water tank is full.

 

[Maggie Anne]

This from goodle search. Alternative Solutions: If the sensor fails, a 620 ohm resistor can be used to bypass the sensor and make the red light turn off, a commonly suggested fix in the Reddit/GoRVing community.
Seems like cutting both wires like you did though would be similar so not sure this is a good suggestions.

 

[fishheadbarandgrill]

Try disconnecting or removing the sensors from the tank all together. My sensors fell of the tank years ago. Always shows green. We just remember to pump out every 4-5 day or when we get fuel. Never an issue for 7 years.

 

[OverTime]

This from goodle search. Alternative Solutions: If the sensor fails, a 620 ohm resistor can be used to bypass the sensor and make the red light turn off, a commonly suggested fix in the Reddit/GoRVing community.
Seems like cutting both wires like you did though would be similar so not sure this is a good suggestions.

Put the resistor across the two wires.

 

[shontm]

We have the same issue and I just want to bypass but cutting one wire, both wires, and wiring together still shows red. Presumably we need a resistor but what type?

 

[OverTime]

We have the same issue and I just want to bypass but cutting one wire, both wires, and wiring together still shows red. Presumably we need a resistor but what type?

Get a multi-pack. Pick one and test it. If it works and doesn't get hot after awhile, you're probably ok.

 

[GZigmont]

Had the same symptoms on both our R-29 and our R-31. The most common cause was some sticky $hit and toilet paper that clings to the inside wall of the holding tank. It stays there after a pump out sometimes. Every once in a while, you need to fill the tank with some water and Dawn dish detergent - or the product that Thetford makes for this. Leave it in for a while and even take the boat out for a spin to get some sloshing. Then pump and rinse a few times.

The other problem that we had on the R-29, was that the only things keeping the holding tank in place, were gravity and luck. Sometimes in rough seas, the tank would shift toward the starboard side and allow the sensor to get too close to the air conditioner return and it would give a false reading. I made some cleats to hold the tank in one spot and eliminated that problem.

 

[georgeboarhunter]

Yet another factory defect that owners are left to deal with without support. I was told to scrape off the sensor, clean it up, and don't let it get near the tank. I zip tied it securely out of the way. Red light went away. I do not consider this "a fix". A fix would be a solution from the factory that involves a working sensor, which the owners paid for, just as auto manufacturers do for factory defects on cars that cost 12% of what this boat cost.

 

[OverTime]

Yet another factory defect that owners are left to deal with without support. I was told to scrape off the sensor, clean it up, and don't let it get near the tank. I zip tied it securely out of the way. Red light went away. I do not consider this "a fix". A fix would be a solution from the factory that involves a working sensor, which the owners paid for, just as auto manufacturers do for factory defects on cars that cost 12% of what this boat cost.

Don't sweat it too bad...it won't be the last thing you will find to fix. My experience with several boats is...the first year of a new boats' life is the commissioning period. You will find plenty of things to change, alter or "fix" to get it to your liking. Much different than an automobile.

 

[venajeff]

I have been looking for a good reliable tank level monitor for my boats and my RVs for 30 years. I have tried capacitance, resistance, ultrasonic, and infrared. The only ones that seem to be truly reliable are the float based ones, which do not work in black water tanks.

 

[OverTime]

The old "flashlight through the tank" trick is what I use. Mine always reads empty...

 

[georgeboarhunter]

Per factory advice for the "fix" i chiseled off the high sensor,scraped off the useless sealant, and zip tied sensor securely facing up into the air. No longer reads full. What about a real fix?

 

[RMarkSampson]

I've heard flushing ice down the head - and then go out for a quick rock and roll will slosh the ice around to help knock things loose within the tank. The ice then turns to water and can be pumped out normally. I have no direct experience if that helps with the holding tank sensors, but I will give this method a shot if needed.

 

[Eagle 2]

I installed a Scad monitor on my CB30, now I know to the 1/8th exactly how much material is in the tank at any time. 2 hour install

 

[BDuP]

Brand new R31 here from three weeks ago and the stateroom head has not worked since our sea trial. Then it showed half full when it was empty. Now it doesn’t work at all. Dealer is waiting on parts. Apparently the “brain” $800. These seem riddled with defective design issues. Manufacturer won’t talk to consumers.

 

[robshepherd87]

I installed a Scad monitor on my CB30, now I know to the 1/8th exactly how much material is in the tank at any time. 2 hour installView attachment 27649

Very intriguing, Eagle 2! Did you just eliminate your factory monitor from the flush system?

 

[Eagle 2]

I installed a Scad monitor on my CB30, now I know to the 1/8th exactly how much material is in the tank at any time. 2 hour installView attachment 27649

Very intriguing, Eagle 2! Did you just eliminate your factory monitor from the flush system?

Nope, I just ignore it, as it’s never really worked right, plus what good is empty, somewhat full and full tell you, the Tecma gauge is worthless, working or not. Knowing exactly how much is in your tank at all times, especially since our CB30 lives on a mooring in a harbor that dye tabs, is crucial. It’s about $225 for the system, if you go that direction, read the instructions carefully and write down your settings you desire so you can input them as it scrolls thru each procedure. It will probably take just as long to install as it does to do the setup. Once you get it, it makes sense, but at first, it’s a bit confusing.