# Testing a Bilge Pump



## Islander7 (Nov 30, 2011)

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!


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## celenoglu (Dec 13, 2008)

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.


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## CorvetteGuy (Jun 4, 2011)

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


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## Islander7 (Nov 30, 2011)

*Thanks!*

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!


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## mitiempo (Sep 19, 2008)

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.


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## MarkSF (Feb 21, 2011)

mitiempo said:


> 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.


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## Rozz (Jun 30, 2011)

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


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## mitiempo (Sep 19, 2008)

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.


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## CalebD (Jan 11, 2008)

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.


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## mitiempo (Sep 19, 2008)

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.


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## SecondWindNC (Dec 29, 2008)

Float switch is usually the first thing to check when a bilge pump isn't working. Regardless of brand/type, they seem to be the weakest link.


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## btrayfors (Aug 25, 2006)

One thing to keep in mind when checking DC circuits with a multimeter is that modern multimeters have a very high internal resistance and, therefore, it requires only a tiny bit of current to get a reading.

You could very well read, e.g., 13.2 volts on the meter, but the circuit itself could be incapable of handling any real load (like a bilge pump). In other words, there could be points of high resistance in the circuit, but they would not show up with a simple voltmeter reading. Areas to look for are: wires and their terminal connections, switches, butt connectors, fuses and circuit breakers, etc. Essentially all parts of the circuit between the power source and the appliance.

I certainly agree that float switches are a common failure point. Most are practically worthless, and will fail after awhile. Some fail open (no pumping) and some even fail closed and partially closed (like the sealed electronic sensor switches). You've gotta spend big bucks for a truly reliable switch, like the Ultra Switches. TEF-GEL - Ultra safety systems - Home page

Bill


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## sfchallenger (May 17, 2011)

Rule does make a pump with the float switch integrated - it isn't actually a float, it is an electronic sensor. Might be a good option if you don't want to replace the float switch and it certainly doesn't hurt to have more than one bilge pump. Personally, I prefer Johnson pumps.


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## fallard (Nov 30, 2009)

After a recent failure of a 6 month old Jabsco "ultra reliable" bilge pump switch--just when it was called to duty for the first time, my recommendation is to test your bilge pump SYSTEM on a regular basis. My main (centrifugal) and auxiliary (diaphragm) pumps are still working and I may be pushing my luck, but I test them regularly and they seem fine. It's the switch I would worry about first: make sure you can test it on a regular basis.

I've considered rebuilding the diaphragm pump on a preventative maintenance basis, but it doesn't seem to want to come apart easily. I may replace the whole pump with a different technology (swash plate?) rather than wait for it to fail.


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## Islander7 (Nov 30, 2011)

My bilge pump has a 3 position switch; auto, off, and man. If I select man, shouldn't that bypass the float switch altogether? Or is the wiring such that any failure in the float switch prevents operation of the pump?


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## sfchallenger (May 17, 2011)

That is correct; the manual position on the switch should operate the pump irrespective of any issue with the float switch. Look for blown fuses, then try to wire the pump directly to the battery. Be careful to make sure you have the polarity correct. Many pumps don't like being wired backwards and will burn out quite quickly.

Good luck.


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## Islander7 (Nov 30, 2011)

Thanks to everyone for your good advice. 
The pump is clearly working, so that's one concern solved. I've borrowed a digital multimeter and it shows over 12 volts at the connections that lead to the pump, so I feel confident that the problem is not with the float switch, as it reads the same both in auto and man. However, when I connect the pump to these leads, select manual, and then check the volts it reads zero. Is this suggestive of the circuit not being able to hold a load? How can I further check this?
Thanks again!


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## GaryHLucas (Mar 24, 2008)

Islander,
You have a bad connection in the wiring. The volt meter draws microamps, even a very high resistance will show 12 volts with a voltmeter and no other load. When the motor on the pump gets connected through the switch the load pulls the voltage right down to near zero. You can narrow this down fairly easily. With the power on and the pump connected measure the voltage at the pump, you said you got near zero. Then measure back farther, at the load side of the switch. If you get 12 volts the switch is good, and the wire is bad between the switch and the pump. Measure at the line side of the switch, if you get 12 volts there, but not after the switch then the switch is bad. Measure back at the connection before the switch. If you get 12 volts there, and not at the switch line connection then the connection to the switch is bad. Process of elimination, but you have to have connected load like the pump to isolate the problem.

Gary H. Lucas


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