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Lutz

Water pump supply problem

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Posted (edited)

Since yesterday, when I open any of the taps, no water. Thinking that the water pump was defective I replaced it, but still nothing. Checked the electrical connection to the water pump and found out that the 12v supply is arriving there when a tap is opened. Checked the replacement water pump and it works OK when connected directly across the battery but when I reconnect it to the said 12v supply it doesn't work. Has anyone got an idea what the cause could be?

 

Edited by Lutz

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How strange, but how are the connections between pump plug and the socket on caravan, any corrosion or bent out of true?

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Sounds like a poor connection / corrosion somewhere.

Enough contact to allow the 12 volts to be seen at a meter, but when current is applied, the poor connection / resistance comes into play and knocks the vootage down to a level that won't run the pump.

 

Check fuse for poor contact.

Assuming you have a pressure switch, short the two wires together - if the pump then runs, its the pressure switch contacts (maybe water ingress?)

 

 

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5 minutes ago, David 38 said:

How strange, but how are the connections between pump plug and the socket on caravan, any corrosion or bent out of true?

 

I'm talking about the submersible pump in the on-board water tank. It is connected to the 12v supply by means of spade terminals which I have also replaced so there can't be any corrosion. Funny thing everything worked until yesterday evening.

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Classic problem, usually loose/corroded/tarnished connections. The bad connection will carry enough current to register the voltage on a meter but not enough to run the pump.

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1 minute ago, AlwynMike said:

Sounds like a poor connection / corrosion somewhere.

Enough contact to allow the 12 volts to be seen at a meter, but when current is applied, the poor connection / resistance comes into play and knocks the vootage down to a level that won't run the pump.

 

 

That's what I assume, too, because I'm getting metered 12v at the electrical connection to the water pump but it drops down to zero as soon as the pump is reconnected. Only where could the poor connection / corrosion be occurring? As all taps are affected (even the toilet flush) it must be somwhere between where all their leads join and the electrical connection to the pump itself.

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Our water pump failed whilst in Spain in December. Mobile engineer said pump was reading as OK on his meter, and it sounded OK, but, when he dunked the impeller in a bucket of water, everything ground to a halt. Turns out one of the impeller 'blades' had picked up a piece of grit and had turned itself into a plastic ribbon that looked like a tapeworm ... 1 new impeller later and all was well.

 

Steve

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6 minutes ago, marchie1053 said:

Our water pump failed whilst in Spain in December. Mobile engineer said pump was reading as OK on his meter, and it sounded OK, but, when he dunked the impeller in a bucket of water, everything ground to a halt. Turns out one of the impeller 'blades' had picked up a piece of grit and had turned itself into a plastic ribbon that looked like a tapeworm ... 1 new impeller later and all was well.

 

Steve

 

It can't be grit in the impeller because a) it's a brand new pump and b) the pump works alright when connected directly across the battery.

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3 minutes ago, Lutz said:

 

It can't be grit in the impeller because a) it's a brand new pump and b) the pump works alright when connected directly across the battery.

It was just a suggestion! Our impeller worked OK connected across the battery; not so when it encountered the water bucket, it wouldn't pump anything. I bought a spare 'for the next time', but forgot to buy the caravan supply that the pump pushes onto. Note to self to buy one when we get back to Scotland - another item for the 'just in case' box of goodies :D.

 

Steve

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Posted (edited)

The voltage can be breaking down anywhere in the circuit, not just at the pump connections. The breakdown can be in either pole too. One easy thing to try is a single wire directly from the pump live terminal to a good live supply, then do the same for the negative. You may identify the location of the failure that way. The failure can also be a broken wire. Also, is the pump switched somewhere because a switch can misbehave in the same way, so eliminate the switch temporarily and you will see.

Edited by Ern
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I guess it must have been corrosion somewhere along the line. While trying to fit a lead to bypass the suspected affected area after locating it roughly with a meter, (there was no obvious corrosion to be seen at any of the connections in between) I must have inadvertently hit the terminal involved and everything suddenly sprang to life again after hours of searching. Much happier now considering we are in a fairly remote part of Spain at the moment, miles from any dealer.

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You still need to identify the fault not rely on "it's working now"... The way to do it is with a  multimeter set on V scale (0-20).  Turn the pump ON  and hopefully running.  Starting at the battery end, at every connection check the voltage between + & -.  You should see a MUCH lower voltage at or after the faulty connection.  

I had a problem like this on the boat, and whilst I had measured Voltage at the end point, this was with no current draw.  When I removed the connection in the end, the +ve side had completely corroded into a copper salt powder, which conducted enough to show the Voltage, but wouldn't carry current

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You’re probably right, but I am fairly confident that I have eliminated the cause. There was no excessive corrosion to be seen at any of the terminals that I was able to inspect. Any more detailed investigation would involve having to remove the fridge, which I would hesitate to do unless absolutely necessary. As it was, I already had to remove all the drawers under the sink unit, but everything was dry there.

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Posted (edited)
23 hours ago, Lutz said:

 

That's what I assume, too, because I'm getting metered 12v at the electrical connection to the water pump but it drops down to zero as soon as the pump is reconnected. Only where could the poor connection / corrosion be occurring? As all taps are affected (even the toilet flush) it must be somwhere between where all their leads join and the electrical connection to the pump itself.

 

Or the negative feed as only the positive comes via the tap switches in parallel.  As the negative affects all it would be my prime target. I would simply "jury-rig" an alternative negative feed to identify that is where the attention is needed. If not then do a  the same "alternative feed test, for the positive. Doing the feeds one at a time, as opposed to doing both, narrows down the issue.

Edited by JTQ

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Actually, it was the positive feed that was the culprit.

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