What is this, exactly?

[Wiley1]

I found this hanging from one wire near my propane shut-off valve.
It appears to be a combination analog tank gauge and sending unit.
I've never trusted the (Empty, 1/3, 2/3, Full) readouts so I didn't even notice when it stopped working.

It appears to be a snap-on thing using four plastic tabs, but one of the tabs appears to have broken off.

Before I repair the wiring and try to get it reattached, I'd like to understand more about how it is supposed to work.
A google search suggests that it might be a 0-90 ohm sending unit.

Attached are three pictures: the top of the gauge, the bottom of the gauge, and the place where it appears to have been mounted.

I found this part which appears to be a direct replacement.
https://www.walmart.com/ip/MANCHESTE...mpaign_id=9383

Questions:
1. To get a new plastic mounting bezel, will I need to buy a whole new gauge and sending unit?
2. If I buy the gauge, will it come with everything I need? Are there any other parts needed?
3. How is this thing able to detect the propane level inside the tank? Why does it have two contact points on the back?

[16ACE27]

It's a propane gauge/sending unit. It clips on and the gauge needle rotates magnetically. The sending unit connects via the TWO wires to the readout inside the MH.

Buy the replacement and clip it on. Normally made by Manchester. Amazon has them for $50.

[OldWEB]

I would first try to save $50 by cleaning the areas up, re-connect the wire(s) and just using electrical tape to secure the sending unit in place. It is not a critical item other than a 'approximate' level of fuel and an even less 'approximate' remote level indicated inside.

[Wiley1]

I'm still totally unclear on how this thing is supposed to work.
I notice that my particular gauge model is intended only for a horizontally mounted tank, so I guess it expects to read a certain resistance at a particular physical point on the tank? And that resistance changes depending on how full or empty the tank is? OK.

But, to measure resistance, wouldn't a current need to flow?
Why are there two red contacts on the back on the meter? Are they supposed to touch something?
What is supposed to hold the meter onto the mounting point? Somebody said it should be glued. Will just any glue work? Wouldn't the resistance of the glue affect the reading of the gauge?

Or maybe it works by ultrasound? Or vibration sensing? Or a little man with a microphone that listens for propane splashing around?

Something about this isn't making sense.
Before I starting slapping Gorilla Glue on it, I'd like to be certain that I'm doing the right thing.

[lwmcguir]

Look it up

Simply a mechanical float with a magnet

[16ACE27]

Originally Posted by Wiley1

I'm still totally unclear on how this thing is supposed to work.
I notice that my particular gauge model is intended only for a horizontally mounted tank, so I guess it expects to read a certain resistance at a particular physical point on the tank? And that resistance changes depending on how full or empty the tank is? OK.

But, to measure resistance, wouldn't a current need to flow?
Why are there two red contacts on the back on the meter? Are they supposed to touch something?
What is supposed to hold the meter onto the mounting point? Somebody said it should be glued. Will just any glue work? Wouldn't the resistance of the glue affect the reading of the gauge?

Or maybe it works by ultrasound? Or vibration sensing? Or a little man with a microphone that listens for propane splashing around?

Something about this isn't making sense.
Before I starting slapping Gorilla Glue on it, I'd like to be certain that I'm doing the right thing.

Your questions were all answered in Post #4.

It clips on.
It is magnetically coupled to a float level mechanism in the tank.

No glue required if it isn't broken.

[OldWEB]

Similar to this.
No one here mentions glue, I would NOT do that, just tape it on (around the outside) and if it has to be replaced then it would be a simple matter to remove.
The two "contact points" are just rare earth magnets for moving the pointer, so there is no connection from the hazardous insides to the real world outside of the tank.

[Wiley1]

Originally Posted by 16ACE27

It is magnetically coupled to a float level mechanism in the tank.
No glue required if it isn't broken.

Yes, in post #2, you said the needle moves magnetically. But, today is the first time anybody has mentioned a float inside the tank.

So, I guess there is something inside the giant nut that rotates?
And, the center of the nut is made of something non-metallic?
And, the two things that look like contacts on the back of the gauge aren't really contacts at all -- they are some sort of dual magnetic sensors?
So, the mechanical gauge would work just fine without the little black sending unit attached?

Now it makes more sense. Thanks.

But, one of my four plastic feet actually is broken off. If I don't want to spend $50 for a whole new gauge, I need to find a way to re-attach the gauge to the big nut. My last concern is whether some glues might interfere with the magnetic coupling.

[Beau388]

Originally Posted by Wiley1

Yes, in post #2, you said the needle moves magnetically. But, today is the first time anybody has mentioned a float inside the tank.

So, I guess there is something inside the giant nut that rotates?
And, the center of the nut is made of something non-metallic?
And, the two things that look like contacts on the back of the gauge aren't really contacts at all -- they are some sort of dual magnetic sensors?
So, the mechanical gauge would work just fine without the little black sending unit attached?

Now it makes more sense. Thanks.

But, one of my four plastic feet actually is broken off. If I don't want to spend $50 for a whole new gauge, I need to find a way to re-attach the gauge to the big nut. My last concern is whether some glues might interfere with the magnetic coupling.

I suggest you go the Manchester Tank site and educate yourself on direct reading and remote reading gauges. I had the same Manchester remote reading gauge on the 44 llb ASME propane tank in my first RV and 1968 UltraVan., so the gauges have been around for more than 50 years. You can still buy an new one if you want. The gauge comes in two parts: internal and external. Replacement external parts are available separately.