Mod Description:

Knowing how much propane you have left always seems to be a guessing game. You tap on the tank to hear the difference in sound where the liquid is. You pour hot water over the propane tanks and where the tank feels cold is where the level is. Then there are those stick on level indicators that are notoriously inaccurate. But if you have two propane tanks, which most towables do, then chances are you also have a changeover valve that switches the propane supply over to the backup tank when the primary tank is empty. An indicator on the top of the changeover valve changes from green to red indicating the switchover has taken place. How do you know this is happening without removing the propane tank cover? Do the propane tank changeover indicator mod of course.

Mod Difficulty:

Remote propane changeover indicator kit - image © 2008 by it's respective owner

LED indicator circuit board showing AA battery holders - image © 2008 by it's respective owner

Backside of circuit board - image © 2008 by it's respective owner

Changeover indicator sensor clips on to changeover valve at the propane tanks - image © 2008 by it's respective owner

Marshall two-stage automatic changeover regulator with indicator - © 2009 by Marshall Gas Products

The black sensor wire at the top is run through the wall along with other factory wiring - image © 2008 by it's respective owner

Circuit board shown from the back in its mounted position - batteries are being used in this configuration - image © 2008 by it's respective owner

LED indicator light showing through wall of dinette bench - image © 2008 by it's respective owner

Removal of battery holders - soldered power supply wires to circuit board - image © 2008 by it's respective owner

Sticky tape on front side of circuit board - used to mount board on backside of dinette bench - image © 2008 by it's respective owner

Alternative to indicator light - uses pressure to determine propane level

Another view of pressure gauge level indicator

To do this mod, you must first verify that you have the correct changeover regulator. It should be a Marshall two stage model 254
Model 254 or equivalent. This type of regulator (see part recommendations below) is required because the indicator sensor in the kit is clipped on to the changeover valve’s indicator bulb. When the valve switches to the backup tank, the sensor senses the change in the changeover valve’s indicator, sending a signal to the circuit board to flash the LED bulb.

Once you have determined you have the correct changeover regulator, you will need to find an opening in the RV wall or floor to run the sensor wire. Try and use an existing entry point, like a factory wiring loom pass-through. This way, you can more easily avoid a water leakage problem if the hole is not properly sealed.

The kit shown requires two AA batteries that need to be installed before mounting the LED box. Install the batteries now. You can test the unit by doing the following:

• Clip the sensor on to the changeover valve indicator bulb.
• Turn both propane tank valves fully on.
• Turn the changeover valve switch to the nine o’clock position so gas flows from the primary tank. The changeover indicator should be green at this point and the LED indicator should be off.
• Turn on an appliance that uses propane, like the heater or stove.
• Turn the gas valve on the primary tank to the off position
• Let the changeover valve switch tanks
• The LED indicator light should begin flashing. If not, be sure the batteries are good, the sensor is clipped on correctly, and the changeover valve bulb indicator has switched from green to red.

Locate a suitable mounting location for the LED box, preferably a place where you can easily see the indicator light from most locations in your RV. The sensor wire in the kit is 25 feet long so be sure the mounting location is not too far away from the sensor. The location should also allow you to run the wire through the wall so the LED box can be mounted flat to the mounting surface. Drill a hole in the mounting surface large enough to pass the wiring through. Use double-sided sticky tape to mount the LED box.

Once mounted, run the wiring to the propane tank area, giving careful consideration to the routing of the wiring near the tank location. You need to be sure that once you have secured the wiring, you can still install the propane tank cover (if you have one). Run the wiring from the bottom of the tank mount up through and to the changeover valve. Use a rubber grommet in the tank mount to avoid chaffing the wiring. That should cover the basic installation for most RVs.

Also shown in the pictures is a modification to the LED indicator itself. As mentioned, the indicator requires two AA batteries to run. Although the indicator requires very little power to run, it may be a hassle to change out the batteries every now and then. It just so happens that the circuit board components in the kit shown can operate on 12 volts.

After checking that the components in the kit you purchased can be run on 12-volts (some brands may not be able to), carefully remove the battery holders from the circuit board. Solder wires at the positive and negative power locations on the circuit board. If you were paying attention to the battery holder connections, you should be able to identify where to solder the new wires. Be sure to make them long enough so for connection to a 12-volt source. Connect the wiring and re-mount. You can also remove the LED indicator box and mount just the circuit board as shown above. Doing it this way requires drilling a small pilot hole for the LED to mount in. RV walls are thin so the LED should poke through enough to see. You can even get fancy and add a small LED bezel to finish off the mounting hole looks.

For those that have a single, permanently mounted propane tank in your RV, such as in a class A, B, or C, there is still hope for you. Most every permanent-mount RV propane tank has a propane level gauge mounted on the tank from the factory. Although it is nice to see the propane level from the tank compartment, you must go outside to see the gauge. There is an alternative similar to the LED indicator. It uses an inline gauge that goes between the tank and the supply hose. The gauge also has a pressure sensor that sends a signal to a display which indicates the level of propane in the tank.

The alternative gauge has a fairly short sensor-to-display wire but fortunately it uses a standard 1/8″ male/female connector. You can buy an extension cable from any audio supply store. The unit runs on a 9-volt battery so you may be able to mod it and use a 12-volt supply as discussed. Another cool feature is that the unit has an audible alarm that goes off when the supply pressure is low. This is nice if you are using a single tank or dual tanks with no automatic changeover valve.

Bet you didn’t expect to have so many options for such a simple indicator, huh?

ModMyRV recommends these parts for this mod:

GasWatch TVL212E Electronic Propane-Level Indicator and Safety Gauge
GasWatch TVL212 Propane-Level Indicator and Safety Gauge
Marshall Gas Controls 254-00 REG 2-Stage Auto Vert
Remote Change-Over Indicator Kit

2 Comments For This Mod

1. Bob Vaughn (December 8th, 2009 at 7:23 am)

   I did this one a couple of years ago then when the batterys kept running down I added an on/off switch so when the TT was in storage I could just switch it off….
2. ModMyRV (December 8th, 2009 at 8:54 am)

   Good idea Bob. Fitting an on/off switch should be very easy to do. Are you referring to the batteries on the indicator box? If so, you should mod the indicator to use the RV’s 12-volt system. I’m sure it would take a bit longer for the indicator to draw down the house batteries…

Let's hear your comments about this mod!