Fuel level sender unit

Hi all,
I have connected up my 2 fuel tank sender units to my Lowrance HDS10.
I am getting no reading from either tank, not sure if I may have connected them up incorrectly or the tank sender units are not working ?
Is there a test I can do with the sender units without removing them from the tanks to see if they are sending a signal ?
Many thanks,
Mike.

 

The HDS-10 has no inputs for tank senders, only two NMEA sockets and Ethernet.
To connect external devices you need something like an NMEA2000 hub or another interface with analog inputs.

 

Yea I got them
Connected by a marine electronics company, they used all the necessary components.
They have told me they that if I'm getting no signal that the sender units in the tanks are faulty.
I have removed the tanks as part of a full boat clean up and was hoping there may be a simple way of checking the sender units
Cheers,
Mike

 

These senders work by percentage of ground, so short the two wires on the sender and you should have a 100% full reading on your gauge. Simply put, pull the two wires at the sending unit and connect them together, at which point the gauge should show as full as it can. If the gauge does show this, the sender is faulty. If the gauge doesn't show this, you have a wiring issue (connection or break) or a gauge related issue.

 

To check the gauge, ground the wire at the sending unit (or if there are two wires, connect them as stated above), and it should read full. That will tell you if your gauge is set up properly. For the sending unit, it should read in the neighborhood of 230ohms (for an empty tank) and 30ohms for a full tank. You probably have to pull the sender out of the tank to move the arm or float up and down. Or you could turn the tank upside down/rightside up and take readings for full and empty, but taking the senders out would be better. It might have dead spots, be stuck or sticking without fuel in the tank,etc. The biggest problem generally is with the ground. It needs to be a clean ground without other components using the wire. Otherwise you get all kinds of erratic readings.