LP tank level gauge repair

I think the magnet fix worked! I tried it just before having it filled, so it's still reading close to full, but at least it is within the range of normal readings. Before, it was all the way clockwise, way beyond F.

Thanks guys!

dougrainer wrote:

Dutch_12078 wrote:
Before tearing the sending unit apart, check the ground and gauge wires for continuity. The sending unit is a float operated variable resistor, and the resistance (typically 0-90 ohms) goes down as the tank level goes up. A poor/missing ground or bad gauge wire connection will cause the gauge to read full.

On edit: There are some tanks that use a reversed sending unit, where resistance (typically 240-30 ohm) goes up as the tank level goes down. On those units, the gauge will read full if the gauge wire is shorted to ground.

His problem is the tank Dial not the inside readout. The dial readout has NO wiring, just the magnetic part. Since the dial is stuck, his inside read will also show full. Doug

Oops! Right you are of course, Doug. As soon as I saw "wires", my mind jumped to the inside panel readout, instead of what the OP actually wrote. Maybe my wiring post will help someone else... :R:S

Dutch_12078 wrote:
Before tearing the sending unit apart, check the ground and gauge wires for continuity. The sending unit is a float operated variable resistor, and the resistance (typically 0-90 ohms) goes down as the tank level goes up. A poor/missing ground or bad gauge wire connection will cause the gauge to read full.

On edit: There are some tanks that use a reversed sending unit, where resistance (typically 240-30 ohm) goes up as the tank level goes down. On those units, the gauge will read full if the gauge wire is shorted to ground.

His problem is the tank Dial not the inside readout. The dial readout has NO wiring, just the magnetic part. Since the dial is stuck, his inside read will also show full. Doug

Here's an image of the gauge on my application:



and of the gauge/float assembly typically used in RV applications:



Therefore, the gauge assembly is screwed into the tank. However, from the top image, it appears the gauge is not rotatable in the housing. Oh well...

For the OP, perhaps removing the gauge to ensure it moves freely would help troubleshoot your issue.

Sounds like the gauge is stuck, but perhaps not the float.
If the float is magnetically coupled to the gauge, then (if I'm reading this correctly), one can remove the 2 screws holding the dial in place and remove the dial w/o emptying and depressurizing the tank, correct?

If that's the case, then the gauge can be removed to check to see if the dial indicator is seized. If not, then perhaps the float is stuck.

(Thread sidetrack...)
Is the dial keyed to the fitting? Mine never hits full, though the marks between 3/4 and full is about a 10th of the rest of the gauge.
I'd like to rotate the dial just a bit so that it actually reads full when it is full. I understand the need for the airspace for expansion, but I feel that the gauge should read full when the tank is as full as it can be.

Before tearing the sending unit apart, check the ground and gauge wires for continuity. The sending unit is a float operated variable resistor, and the resistance (typically 0-90 ohms) goes down as the tank level goes up. A poor/missing ground or bad gauge wire connection will cause the gauge to read full.

On edit: There are some tanks that use a reversed sending unit, where resistance (typically 240-30 ohm) goes up as the tank level goes down. On those units, the gauge will read full if the gauge wire is shorted to ground.

Chris Bryant wrote:
The outside dial is magnetically coupled to the float inside- often you can just take a small magnet (or magnetic screw driver) to move the dial and couple it again.

They sometimes stick (the dial needle) and by using the Magnet you free it up. You use the magnet to go empty and when you reattach to the tank it should go to the corect level. It is possible for the float in the tank to stick. That is easy to fix by driving the vehicle on sloped bumpy roads. Doug

The outside dial is magnetically coupled to the float inside- often you can just take a small magnet (or magnetic screw driver) to move the dial and couple it again.

My 55 gal vehicle tank had a sending unit attached to the float, cut 2 wires, unscrew 2 screws, replace and rewire. My float still worked, the sending unit/gauge no longer worked so I replace the sending unit without draining the tank. LP dealer ordered the new sending unit.