Testing a Bilge Pump

[Islander7]

Hi,
Recently my bilge pump failed me. It was a Flojet Pump # 04125-114. I bought a multimeter which I think showed that the pump was getting good power, so I assumed the motor what shot. I bought a new pump of the exact same model online, but when I connected it, the pump wouldn't run. I can't tell if I just wasn't using the multimeter correctly or if the new pump is faulty. Is there another way to power the new pump to see if it works or any other way to troubleshoot this problem?
Thanks!

[celenoglu]

A multimeter is a good device if you know how to use it. To be sure connect your pump directly to your batteries terminals for a short time. These pumps can run dry. If pump is working check your circuitry specially float switch you have one.

[CorvetteGuy]

I would agree,, hook up the pump directly to the battery, who know now you probably have a spare bilge pump. Digital multimeters are easier to read as opposed to analog ones the settings must be right or false readings can be taken if not read correctly

[Islander7]

That was good advice, I hooked up the pump to the battery and it worked like a champ. Then just out of curiosity I hooked up the old pump and that one worked too. I'm stArting to think I'm using the multimeter wrong, the needle was fluxing when I tested the power at the pump and I just attributed it to me not holding it steady. Is there another way for me to troubleshoot this issue? Thanks for your help!

[mitiempo]

First, a digital multimeter is easier to use.

I would start at the battery where the bilge pump wires start and check the connections there. Make sure they are not corroded, then work your way to where the pump is mounted. If the wires are old a replacement is a good idea - one piece without connections from power to pump or float switch if you have one.

[MarkSF]

Originally Posted by mitiempo

First, a digital multimeter is easier to use.

I would start at the battery where the bilge pump wires start and check the connections there. Make sure they are not corroded, then work your way to where the pump is mounted. If the wires are old a replacement is a good idea - one piece without connections from power to pump or float switch if you have one.

The pump doesn't just need 12V on the live terminal, it needs a ground on the other terminal to complete the circuit.

The best way to test it is as follows :

Connect the red probe to the + terminal on the pump, and the other to a ground. Where to find a ground? The engine, a negative battery terminal, or often the through-hullss are grounded. In volts mode you should get around 12V.

Then set the meter to resistance mode. First connect the two probes together, that should give 0-1 ohms on the display. Good, the meter is working. Now test between the - terminal on the pump, and ground. You should get around 0 ohms. Anything over one is bad.

I suspect you will see infinite ohms because the float switch isn't closed to complete the circuit. So close the float switch and see if that starts the pump and brings the resistance reading down to about zero. I suspect it will not, as the float switch is faulty.

The float switches seem to fail about as often as the pumps, btw.

[Rozz]

best way to see if the pump windings are bad is ohms check. google for pics lol

[mitiempo]

MarkSF

My suggestion was for all wiring, positive and negative.

If measuring impedance between the negative terminal on the pump and a good ground the float switch shouldn't make any difference - float switches switch positive in any I have seen or installed.

If the wiring is old it is probably corroded and may not even be tinned or properly sealed at the connections. It is easier to re-wire than troubleshoot in this case.

The pump windings may be suspect on the old pump but certainly not on the new one.

[CalebD]

I've got nothing good to say about using a diaphragm pump as a bilge pump. Been there, done that.
Now we have a Rule centrifugal pump sitting in the bilge that costs 1/4 of what a diaphragm pump costs. If it breaks it wont cost $200 to replace.

[mitiempo]

I've always use Rule pumps in various sizes and that is usually what I recommend and install for others as well.

Not only are they inexpensive but durable - it is the float switches that die most often.