Bilge pump internal short?

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webcraft

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Rule 500gph sump bilge pump keeps blowing fuses. It was pretty oil-contaminated for a while.

There's a live and a neutral coming out of the pump (brown and blue).

Multimeter on continuity setting across these two sounds the buzzer.

Does this mean:

a) There is a dead short inside the pump

b) Pump is FUBAR?

- W
 
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can you spin the thingie at the end? Probably stuck, internal resistance too high, burns fuse.
If you can loosen the shaft and it starts spinning, it may work for a week or do before locking again and starts burning fuses.
If that's the case, save your time and scrap it now...

V.
 
The brown is probably pos and the blue earth. No neutral on a DC system.

If it turns easily and will spin connected across a battery with no fuse hooked up without stopping or getting hot it might be a DC fault elsewhere in the circuit.

We bought a boat that would not clear the bilge once - the blue and brown were hooked up wrong and it was sucking instead of blowing. Some run in reverse if so connected.

Good luck with a fix and stay safe.
 
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odd, fubared most likely...
in theory it's sealed so oil contamination shouldn't affect it.
worth checking it directly on a battery just to see if it works...

V
 
rotrax said:
The brown is probably pos and the blue earth. No neg on a DC system.
Click to expand...

Sorry, that's totally wrong. 12VDC is positive and negative, there is no earth. (despite what car manufacturers called "positive earth" or "negative earth".

There is also no live and neutral (note to OP), although we do often refer to "live wires".

Bizarrely, Rule refer to the black wire (negative) as being "ground" !
 
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webcraft said:
Rule 500gph sump bilge pump keeps blowing fuses. It was pretty oil-contaminated for a while.

There's a live and a neutral coming out of the pump (brown and blue).
Click to expand...

Rule wiring is usually brown = positive and black = negative (not normally a blue wire present.

Multimeter on continuity setting across these two sounds the buzzer.

Does this mean:

a) There is a dead short inside the pump

b) Pump is FUBAR?

- W
Click to expand...

If you can turn it easily by hand, it's knackered.
 
PaulRainbow said:
Sorry, that's totally wrong. 12VDC is positive and negative, there is no earth. (despite what car manufacturers called "positive earth" or "negative earth".

There is also no live and neutral (note to OP), although we do often refer to "live wires".

Bizarrely, Rule refer to the black wire (negative) as being "ground" !
Click to expand...
I’m intrigued by your reply which I’m sure is correct, but not the whole story, I think. I always think of DC systems as positive and negative, but I also know a lot of boat systems ground the negative (I do) so for my typical setup I would describe the wires as positive and negative (which is grounded).
 
Have sitting on my bench two Whale low profile pumps, both failed after about 18 months,
One failed because water seeped past the rubber "O" ring and got into the electric motor compartment.
One would still run on manual overide but not auto,something had seriously overheated and melted the case.
Both the impellers would turn.
 
RupertW said:
I’m intrigued by your reply which I’m sure is correct, but not the whole story, I think. I always think of DC systems as positive and negative, but I also know a lot of boat systems ground the negative (I do) so for my typical setup I would describe the wires as positive and negative (which is grounded).
Click to expand...

No argument here, You can ground the negative, but it's still a negative, it doesn't become an earth wire :)

Rotrax has, i know, a history with motor cycles, so i guess that's where he gets the terminology of "earth from". When i worked in the car trade the negs were always referred to as "earth". No doubt as a result of "negative earth".

Moving on, with boat systems, how about negative returns, isolated returns, grounding negatives, bonding negatives and bonding DC neg to AC ground...................................... :) :)
 
PaulRainbow said:
Sorry, that's totally wrong. 12VDC is positive and negative, there is no earth. (despite what car manufacturers called "positive earth" or "negative earth".

There is also no live and neutral (note to OP), although we do often refer to "live wires".

Bizarrely, Rule refer to the black wire (negative) as being "ground" !
Click to expand...


Quite right Paul - I meant to write 'no neutral', not no neg.
 
webcraft said:
Why?

Others have said the opposite.

- W
Click to expand...

Please point me to one post in this thread that states the opposite ?

The fuse is blowing because it's being overloaded. This can be because it's jammed or blocked, or because the motor is internally shorting. You have said the pump rotates easily by hand, ergo it's internally shorting.

Your continuity test with the multimeter is a red herring, A good motor will have a low enough resistance to set the audible alarm off, a burnt out motor will often do the same, so it's a meaningless test.
 
PaulRainbow said:
Please point me to one post in this thread that states the opposite ?
Click to expand...

Post #2

It's a tiny little motor, why would it not be expected to turn by hand?

I refer you to Bilge Pump Troubleshooting - BoatUS Magazine

"With power off and the pump withdrawn from its mounting bracket, try to turn the impeller by hand. It should rotate freely with a finger."

- W
 
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PaulRainbow said:
......Rotrax has, i know, a history with motor cycles, so i guess that's where he gets the terminology of "earth from". When i worked in the car trade the negs were always referred to as "earth". No doubt as a result of "negative earth".....
Click to expand...

Or "positive earth", if you're old enough to remember.
 
PaulRainbow said:
I think that your pump is in excellent condition and will work perfectly OK, even without a fuse.

Happy now ?

Oh, my name isn't Simon.
Click to expand...

So you disagree with the BoatUS article I linked to which says you should be able to turn the impeller by hand?

impellor.jpg

And with the poster in post #2, who also thought it should be able to be turned by hand?

I asked you a simple question, why do you think the fact that you can turn the impeller by hand means the pump is knackered, and you replied with a 'clever' remark. FYI, I could turn the impeller by hand when the pump was new, and it worked fine for a year.

Strangely, you are right about one thing, it works perfectly without a fuse. if connected directly to 12 volts.


- W
 
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