Upgrading My RV Tank Level Monitoring System

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The See Level II Tank Monitor

Well, I finally bit the bullet and laid out some hard earned cash on a new RV tank level monitor called the SeeLevel II from a company called Garnet Instruments. The hefty price tag of $280 bucks Canadian (less in USD) had always held me back from this upgrade. But with a birthday on the horizon, I decided to treat myself. I needed a new “want to have but not gotta have” gadget.

I thought it would go hand in hand with the recent storage box upgrade I made to my Waste Master sewer system. I scanned the multiple product offerings on the Garnet website and settled on the SeeLevel II model 709-4PH.

It comes with four tank level sensor strips to cover my fresh water and black, gray and galley waste tanks. The display unit also contains two switches. One for my Suburban water heater and one for the new Shurflo water pump plus a button to show the current battery voltage.

Tank and Battery Level Display Panel

The SeeLevel II monitor will be a “night and day” upgrade over the existing OEM dummy light readout package which rarely works correctly and only displays four levels (empty, 1/3, 2/3 and full). The model I purchased will be a complete replacement for the existing panel.

The SeeLevel II promises to be much more accurate utilizing a digital readout showing percentage full. Rather than using four metal sensor pins inside the tank, it uses an external stick-on sensor circuit strip which will never foul leading to inaccurate readings.

Unboxing the SeeLevel II 709-4PH

Installing the SeeLevel II RV Tank Level Monitor

Control Panel Wiring

Luckily the SeeLevel can use the existing OEM monitor’s wiring saving the hassle of fishing new runs though the rigs bowels. I decide to start with wiring up the control/display panel first, before venturing underneath the rig to attach the four tank sensor strips. I pulled off the OEM tank monitor display box and holy crap. It looked like my Cougar had barfed up a wire fur ball!

Cougar Tank Monitor Panel Wiring

Lucky for me I have decades of experience in electronics repair otherwise, it would be quite intimidating. One thing those years have taught me is the best approach to a complex task is “divide and conquer.”

So I set to work with the aid of my multimeter separating each circuit, figuring out which wire did what. As you’ll see in the video at the end of this article, I was able to greatly simplify the wiring mess with the SeeLevel II connection harness.

Cleaned up wiring

Once I completed attaching the wires, I performed a quick test confirming proper operation of the water pump, water heater switches, and battery reading. Looking Good! At this point the waste tanks read as an open circuit, to be expected since I hadn’t installed them yet.

Opening Up the Belly of the Beast

Our Keystone Cougar fifth wheel has a thin coroplast underbelly and reflective bubble insulation covering screwed to the frame. Over the years I have had to pry it back multiple times to do repairs and modifications so was well aware of the tank placement and where the tank level sensor wiring ran. Even so, I wasn’t looking forward to the job. I knew the workspace was going to be cramped.

Under the rig looking at fresh water tank

I used my cordless impact driver to undo some of the 3/8ths self-tapping screws to gain access. Plus, I have over time cut myself some flaps to get into certain areas. When done I seal the seams with Gorilla tape.

Installing the SeeLevel II Sensor Pads

The wire hook up was dead easy. I just had to splice the two wires from the SeeLevel sender pad to the existing sensor wires. Blue to blue and black to white. The SeeLevel II uses a common bus to transmit tank level information digitally back to the panel. Because of this, the next step is critical.

I needed to program each sensor for the tank it would monitor. This is done by simply snipping off a small tab at the top of the sensor strip. The control boxes brain can read which tab is missing and therefore knows which tank it is measuring. The default program is no cut tabs which indicates the fresh water tank.

Sensor Tabs

Once the sensor strips are connected and programmed, the next step is to mount them on the tank side using temporary tapes, like duct or masking. You want to make sure they are reading accurately with strong signal strength before peeling off the 3M backing film and mount them for good.

For final mounting the owners manual suggests sanding down the proposed mounting area’s surface, clean it with acetone and make sure it’s at least 2 inches away from any metal. Being too close to the frame could impact the signal. Finally the two sensor wires at the top and need to be dressed off to the right of the strip.

Initial Test and Control Panel Wall Mount

With the sensor strips all taped on and wired up I headed back inside the RV to check the display. Success! I had percentage readouts on all four sensors. Now I could mount the display panel on the wall. It’s a flush mount type panel, but unfortunately, the existing cutout was a little too tall. To remedy this, I purchased a run of the mill electrical outlet plate and modified it to fit.

SeeLevel display wall mount

Doh! Big Screw Up Made

In my haste to order the SeeLevel II system, I neglected to measure my waste tanks for height. In my mind, I figured they must be at least 10 inches. So when ordering the 709-PH4 kit, I went with the default 13″ (710ES) sensor strips. In hindsight, I now realize I have reduced the resolution and accuracy of the system.

710es sensor

Once I got under the rig and measured the tanks, they ended up being more like 7 1/2 inches tall. Which I figured was OK, I’ll just cut the sensor strips down in size as shown in the install manual. The only problem with that was the bottom of the waste tanks are curved causing the end of sensor strip to stick out. Not wanting to try to bend them I went and cut them to 4 1/2 inches so they would stick to the flat area of the tank side.

710js sensor


The shortened sensor pad works, but now I only have three 1 1/2 inch sections left on the strip to do the level measurements. If I had been smarter, I would have made sure of the tank heights beforehand. And ordered the optional shorter (710JS) tank sensor strips. The (710JS) uses 1-inch sections so I would have had five sections leading to better resolution. Oh well, live and learn. At least I can pass my mistake along and prevent it from happening to you.

Video Detailing the SeeLevel II Installation

Stay Tuned For a Full Review

Currently, my fifth wheel is in storage, so a final placement of the sensors is not a smart idea. I need to make sure the rig is level and experiment with empty and full tanks, etc. before I peel the backing and stick them on. I’ve used 3M adhesives before and you usually only get one shot.

In a few weeks, I’ll be back on the road and in an RV Park where I can play around with it to my heart’s content. After thorough experimenting and using the new RV tank level system a bit I’ll come out with another posting sharing my findings and thoughts on this upgrade.

See More Love Your RV! Mods and Upgrades

Installing My New SeeLevel II RV tank monitor panel into our Keystone Cougar fifth wheel trailer by the Love Your RV! blog - https://www.loveyourrv.com/rv-tank-level-monitoring-system/ #RVing #RVupgrades

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