Could you identify this?

[TorronaPwr]

Hi and thx for any help in advance. On my TANKWATCH 4 display monitor for the black water tank, the red light designating the tank full is not working ( and resulted in an unfortunate situation lol). Do you know if this is an LED which can't be replaced, or a bulb which can? If it can be replaced how do you get it out? Bayonet? Screw? I tried gently both types but didn't want to break it. Would like to save $$$$ for a replacement monitoring system

 

[KnotYet]

Those are LEDs.
LED's seldom burn out but you can test the leads for input voltage when the sensor should
have triggered, i.e, when the tank is full. If you have a good VOM you can also test the LED.
The LED may be permanently crimped in place but you can clip one of the leads for testing.

It is way more likely that the problem is the sensor.
LEDs typically operate at 3-5 VDC and are diodes, thus polarity sensitive.
If you determine it is the LED, they are very cheap and readily available. I have hundreds...

 

[TorronaPwr]

Excuse my lack of electrical knowledge - if it is the LED can I cut the wires and attach the new LED to those wires to avoid having to solder to the circuit board?

 

[KnotYet]

Yes, it looks like there is enough wire to do what's needed if the LED is in fact the problem.
As I posted before, the sensor or related circuit is more likely.

 

[TorronaPwr]

If I understand correctly, I need to wait until tank is full before checking the leads for voltage. If I have current then I can check the LED - by voltmeter at the stem of LED?

 

[KnotYet]

If you have 3-5VDC you can check the LED. Try it both ways, 3-5VDC reversed won't harm it.
You can check LEDs using the VOM's ohmmeter function.
Once it is isolated from the circuit, try the VOM both ways.
One way the resistance should be low and the other way it should be high.

 

[Mac2]

I have sad news for you. I have the same setup. The probes have a sensor that slides up a pole and contacts the other sensor to close the circuit and activate the “full” light. It routinely gets debris between the probes, which in turn, fails to activate the light. I have three probes and they have all malfunctioned at one point. The probes are easy to clean and check before reinstalling. Just not pleasant.

 

[Nordlund Xpress]

We had the same tank sensor issues reported by Mac2 in our last boat. We gave up cleaning them as the problem just repeated itself. We did not love the system. The Head Hunter Tank Sentry system in our current boat works well. If starting over, I would start looking at the ultrasonic external tank sensor options now on the market and avoid having parts inside the black water tank.

 

[Jeff F]

I have same unit that's never worked properly.

 

[TorronaPwr]

Yes, you were correct, after testing it must be the in tank sensor itself that is the problem. I can't complain as it's 20 years old so now it's time to investigate an external tank monitor system and smash open the piggy bank Thx for all the input.