Why Are My RV Sensors Not Working? How Do I Fix Them?

June 25, 2020

Why are my rv sensors not working and what can I do to fix them?

Key Points:

  • Black tank sensors misread because poop and toilet paper are caked on them and gray tank level sensors misread because they become layered with food grease, causing them to read “full” when the tank is only partially filled. 
  • Restoring both black and gray/galley tank sensors is an easy process described in our guide on How to Clean and Restore RV Wastewater Sensors.
  • When sensors still misread after multiple cleanings, they may just need to be replaced.
  • The best way to prevent misreading sensors in the future is to follow The Unique Method.

Why are my RV holding tank sensors not working? An age-old question. Even many experienced RVers give up on the hope of fixing their RV sensors because they are such sensitive, poorly-made devices and can break or malfunction easily. In fact, some people just gauge their habits and take a guess at when their black or gray tank is nearing full because they believe they’ll never be able to rely on their sensors to tell them the truth. We’re here to dispel the myth that you can never trust your sensors. If you are using the right products and practicing the right care habits, that crumbled wall of trust between you and your sensors can be restored!

In this article, we will walk you through why your RV tank level sensors are malfunctioning, give you resources on how to fix this problem, and prevention advice so you don’t deal with RV holding tank sensors not working in the future.


Why Are Your Holding Tank Sensors Not Working?

Sensors malfunction for only two reasons:

  1. Something is covering the sensor
  2. Sensors are broken

Different things can cover the sensors depending on the type of tank. Below, we will give you a brief description of what could cause both black and gray sensors to misread, but if you want more information on how the sensors work and the pros and cons of popular cleaning techniques/products, refer to the Cleaning RV Holding Tank Sensors guide.


Black Tank Sensors

Poop and toilet paper can cake onto the surface of your RV sensors, which causes them to read “full” when the tank is actually only partially filled. Even if you are applying bacteria-based tank treatments to properly liquefy the waste, you can still experience misreading sensors if you are not flushing your tank after each dump. Holding tanks drain using gravity and nothing else. Imagine a sink full of dirty dishwater draining; grease and food particles easily get stuck to the sink walls as the waterline slowly recedes. The instinct is to use the spray nozzle in your home kitchen to rinse those clingy particles off so they don’t cause damage/stains on the sink walls. It’s the same principle with black tanks. Even the most liquefied waste can cling to the walls and sensors as it slowly drains out.

TP is one of the usual suspects when it comes to misreading black tank sensors; be careful to not use too much. You don’t have to use specifically RV toilet paper, but without using a good bacteria-based, waste-digesting treatment product, top brand toilet paper can take longer to break down than RV toilet paper and get snagged on sensors. Using bacteria-based products requires an ample amount of water in the tank so the bacteria can survive, flourish, and reach the waste. Extra water also helps keep large chunks of waste and TP off the sensors, so be generous with water when flushing.


Gray Tank Sensors

Savvy RVers understand that solid food waste shouldn’t be allowed to go down your drain lines and end up in your gray/galley tanks. Even if you go to great lengths to make sure no food waste, grease, or debris ends up inside your gray tank, some will inevitably end up there. When you wash your dishes, pots, or pans (even though you have scraped them clean and maybe even wiped them), some residual food grease will get washed down the drain. The same sink analogy applies to the gray/galley tanks; when dumping, gravity slowly causes the water level to decrease, which allows grease and oils to cling to walls and sensors on the way down, so make sure you make a point of flushing the tank each time you dump.

Hook-up campers don’t need to worry as much about the stealthy bits of grease getting in there because they typically keep their gray tank valves open, which means that grease and oils don’t have a chance to block the holding tank sensors because the waterline never gets that high. Dry campers/boondockers who must keep their gray tank valves closed can experience a slow buildup of this residual grease on the tank walls and sensors as the waterline sits idle for periods and slowly rises with continued use. Eventually, even small amounts of built-up grease that haven’t been rinsed can cause your sensors to read "full" all the time. 

Besides food waste and cooking grease, hygiene products like soap, shampoo, and toothpaste will end up inside your gray tank as well, not to mention human hair (which can cause super nasty odors); the combination of these and food grease can make for a powerful concoction of slime that can easily cause tank sensors to misread. But removing this greasy layer is easy and inexpensive and can be done overnight while you sleep!

Note: How you use your grey water valve can have a huge impact on your sensors, so refer to our Definitive Guide to Using Your RV Waste Water Valves guide for detailed information on how to use your RV wastewater valves as responsibly as possible.


Cleaning and Restoring Your RV Holding Tank Sensors

Restoring your malfunctioning sensor probes is easy and affordable for both black tanks and gray/galley tanks. For black tanks, the best product to use is Unique Sensor Cleaner and we recommend Dawn Ultra dish soap for cleaning and restoring gray/galley tank sensors. We have provided an easy process to restore them all in our guide on How to Clean and Restore RV Holding Tank Sensors. Black tank sensor restoration can be a little more challenging for full-timers who need to use the tank while cleaning the sensors, but we have that modified process covered in that guide too!


Preventing Sensor Issues

It’s so satisfying when you have fixed a misreading sensor and are now enjoying the luxury of your RV with the confidence that your tank is as full or empty as the level monitor indicates. 

Because misreading sensors can cause serious anxiety in the middle of a trip, we recommend adopting The Unique Method to prevent sensor misreadings in the future. The Unique Method is a proven process for caring for wastewater holding tanks. It is a 50/50 approach: 50 percent the right care habits and 50 percent the right products. We also recommend that dry campers and boondockers use our Dry Camper Pack, which includes a helpful guide and all the necessary treatments to keep your tanks clog and odor free!




Adopt The Unique Method

You bought your RV so you could enjoy life and spend time with family and friends. The last thing you want to do is waste precious time and money on fixing wastewater holding tank problems. Keeping your tanks in peak operating condition doesn’t have to be hard, confusing, or expensive if you follow our proven process: The Unique Method.

The Unique Method is a comprehensive tank care plan that we developed after years of conversations with real customers facing real problems. The Unique Method provides you with simple, preventative steps to stop odors, clogs, and sensor problems before they start so you can spend less time worrying about your holding tanks and more time enjoying the freedom and adventure of RVing. Try it yourself and see why thousands of campers trust their RVs with The Unique Method every day.

If you need more help with anything covered in this guide or simply have a comment, we’re here to help you anytime!

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