Low voltage at bilge pumps

[Gypsy Diver]

My little trawler has two bilge pumps that work off the same breaker. Both have their original wiring as far as their respective terminal blocks. Both pumps have stopped working. There is proper voltage of about 13 volts at the breaker. But with the breaker on there are only about .25 volts at either terminal block. With the breaker off there are zero volts at the terminal blocks for the pumps, which is normal. Does anyone have any ideas?

 

[ScottRhodes13]

Does the wire go to a float switch before the pump?
Also, how good is the ground at the pump?

 

[Gypsy Diver]

Thanks for your reply. I can disconnect the float switches for both pumps, and the pumps themselves. That's not the problem because there is only .25 volts at the terminal blocks where the wires from the breaker switch bring power to the float switches and the pumps.

 

[tiltrider1]

You have a corrosion problem some where. Start at the bilge pump and work your way to the circuit breaker testing voltage. When you find the jump in voltage you will have found the corrosion.

 

[ScottRhodes13]

When measuring voltage, are you using the same connection point for the negative probe at both locations? Just trying to determine if the problem is with the positive or negative side of the circuit.

 

[SteveK]

Have you checked at the breaker with volt meter, both sides positve in and positive out to rule out breaker to a known ground.

At this point the ground location has not been established as good. find a another known positive + and touch to the ground wire near the pump with volt meter.

You can run a wire strand from breaker load side to check continuity on the positive wire at the terminal end. does not have to follow the existing wire or be fancy.

 

[Gypsy Diver]

You have a corrosion problem some where. Start at the bilge pump and work your way to the circuit breaker testing voltage. When you find the jump in voltage you will have found the corrosion.

Thanks!

 

[Taras]

On such a critical safety system as a bilge pump, it maybe best to run new wires from the breaker to the pump.

 

[Nick F]

On such a critical safety system as a bilge pump, it maybe best to run new wires from the breaker to the pump.

Good advice!

 

[Comodave]

I always calculate the size wire required for a 3% voltage drop and then go one size larger wire. That way I get excellent voltage at the device.

 

[DennisB1]

I would first check the function of the circuit breaker as you said both pumps failed power with the same CB. Disconnect the wire output from the CB it should be the same as the input 13v range. If ok clean the connectors to each pump and the return ground. With both pumps failing it’s good to start at the source. Next check to see if each pump works with power on by lifting each float switch. If they work good. Next would be to would be to check continuity using an ohm meter it should be in 2 to 5 ohm range depending on the pump size.with the float switch in the on position.
Next work on the pump end cleaning connects. Also check the pump/float switch resistance it should be in the 1 to 5 ohm range. If it’s ok the problem could be in the wire runs. It’s a process of checking voltage and resistance using a good voltage/ohm meter.