Have I been conned?

KREW2

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Well! it's only a fiver, but anyway.
At the boat jumble I bought a 12v diaphram pump. The stall holder connected it up to a battery and it ran quite sweetly.
It has the conventional red+ that goes straight into the motor, and a Black- that goes into what looks like a capacitor, exits into an in-line fuse, and then into the motor.
Today I hooked it up to a battery and nothing, fuse is ok. Is there something the seller could have done, ie charged up the capacitor, or sommat to make it work on a temporary basis?
 

exfinnsailor

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Fuse on the negative terminal is a bit rare. It means if it blows the unit is still live and it could have an internal short that would not be protected by a fuse. Try it the other way round. Your not going to do alot of damage to something that is dead.
 

KREW2

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Fuse on the negative terminal is a bit rare. It means if it blows the unit is still live and it could have an internal short that would not be protected by a fuse. Try it the other way round. Your not going to do alot of damage to something that is dead.

The fuse is between the capacitor and the motor. Are you suggesting I put red to black aand black to red.
 

davidej

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If the pump does have a capacitor it must be in parallel with the motor -not in series.

DC won't pass thru a capacitor -if it has one the purpose is to stop radio inteference from sparking at the brushes.

Have another look at what you suggest is a capacitor - it may be surpflous to requirements

But as someone said - only a fiver!
 

maxi77

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If it is a capacitor then it will not work uless the capacitor is shorted out. Capacitors do not pass DC current. Have you checked continuity with a meter or test lamp.
 

Ubergeekian

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Well! it's only a fiver, but anyway.
At the boat jumble I bought a 12v diaphram pump. The stall holder connected it up to a battery and it ran quite sweetly.
It has the conventional red+ that goes straight into the motor, and a Black- that goes into what looks like a capacitor, exits into an in-line fuse, and then into the motor.
Today I hooked it up to a battery and nothing, fuse is ok. Is there something the seller could have done, ie charged up the capacitor, or sommat to make it work on a temporary basis?

It won't be a capacitor. Maybe some sort of inline choke for RF suppression. Try feeding the fuse directly.
 

Ubergeekian

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You didn't bother reading the thread again, did you? There are better ideas in earlier posts that have already been confirmed as correct by the OP. :rolleyes:

I started answering, got called outside to join in a barbecue, came back in stuffed with carbonised chicken and hit "Submit reply". So sue me. And it still wasn't a capacitor!
 
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