Electrical problem

[The Welsh Cruiser]

24 minutes ago, Sea Dog said:

I thought from an earlier post that @Tash and Bex was coming to see you tomorrow? Might it not be best to await the cavalry at this stage?

You're probably right but I stubbornly try to do things myself if I can! This has held me in good stead, mostly, but I am a bit nervous about this one.

[ditchcrawler]

5 minutes ago, The Welsh Cruiser said:

You're probably right but I stubbornly try to do things myself if I can! This has held me in good stead, mostly, but I am a bit nervous about this one.

Just wait for conformation, if you are right it will be a confidence boost and if wrong save a lot of hassle

[Tony Brooks]

34 minutes ago, The Welsh Cruiser said:

I think I know how to bypass the switch but could only do it by wrapping a bit of wire around a ring connector, then a joint at the other end by twisting 2 wires together. I don't have any crocodile clips or similar. I'm a bit nervous about doing it to be honest, but might just give it a go. 

You could easily bypass a typical switch by using a screwdriver, knife blade, fork or spoon handle to  join the two terminals on the back of the switch. If the motor then runs you will have proven it is a resistive switch. You will NOT get a shock and as long as you keep the metal of the blade away from the metal of the boat nothing startling will happen.

 

If the switch is OK you do the same to the fuse and then if the motor runs with the switch on you have proven a faulty fuse assembly, it may or may not be the actual fuse.

 

However I agree with Sea Dog it may be best to wait for help.

 

At present while you are only using terminals on the back of the switch/fuse panel for meter connections I am about 80% sure that you are in fact measuring volt drops between positives of one sort or another and not "normal" voltages. Volt drops are very useful for those with experience but are usually very confusing for most  boaters. At present I have seen no confirmation a true negative has been fund from which to measure voltages and it is also not been proven if the fault is in the positive or negative side of the circuit. This is why waiting for help is probably a good idea.

[Tony Brooks]

From post 27 I think this is your circuit so no negatives anywhere near the switches and fuses. Hope it helps.

 

[The Welsh Cruiser]

1 hour ago, Tony Brooks said:

From post 27 I think this is your circuit so no negatives anywhere near the switches and fuses. Hope it helps.

 

Thanks Tony that matches what I can make of what I can see. I'm going to re connect the pump, check everything I can then attempt to by pass the switch and fuse. I'll post again when I've tried this.

[The Welsh Cruiser]

This is becoming a bit of a nightmare! I've re-done the wiring connections around the pump with the intention of by passing the switch to see if the pump runs.

 

The factory wires from the pump are attached to my live feed with screw connectors. My live feed shows the same voltage as I get at the switch. Good so far. However, when I connect the wires from the pump to the positive and negative feed my meter shows a few milliamps then slowly drops back to zero. I think this indicates a short circuit. How can this be? I've connected the pump wires directly to a battery on several occasions and the pump runs, indicating that there isn't a short circuit.

 

I'm going to wait for Bex to arrive before doing any more but I'm curious, what's going on here?

[Sir Nibble]

Lord above! Friend, electrics is not for you. There are basic truths about the nature of electricity and how to understand how to use test instruments and interpret the results which you don't have a handle on. Stop now.

[The Welsh Cruiser]

4 minutes ago, Sir Nibble said:

Lord above! Friend, electrics is not for you. There are basic truths about the nature of electricity and how to understand how to use test instruments and interpret the results which you don't have a handle on. Stop now.

I know, and I've stopped! I like to learn though so, in time, I won't have to ask such ridiculous questions  

[tree monkey]

51 minutes ago, The Welsh Cruiser said:

This is becoming a bit of a nightmare! I've re-done the wiring connections around the pump with the intention of by passing the switch to see if the pump runs.

 

The factory wires from the pump are attached to my live feed with screw connectors. My live feed shows the same voltage as I get at the switch. Good so far. However, when I connect the wires from the pump to the positive and negative feed my meter shows a few milliamps then slowly drops back to zero. I think this indicates a short circuit. How can this be? I've connected the pump wires directly to a battery on several occasions and the pump runs, indicating that there isn't a short circuit.

 

I'm going to wait for Bex to arrive before doing any more but I'm curious, what's going on here?

I'm with sir nibs here.

 

Also I have massive sympathy with you, electrics are the devils work but having someone actually point and show will clarify much of the confusion, taking stuff apart at this point could make the magic smoke escape.

 

I have now learnt to back away from electrical stuff unless I completely understand what's going on, each time something else goes wrong I learn a little bit more, baby steps

[Tony Brooks]

2 hours ago, The Welsh Cruiser said:

This is becoming a bit of a nightmare! I've re-done the wiring connections around the pump with the intention of by passing the switch to see if the pump runs.

 

The factory wires from the pump are attached to my live feed with screw connectors. My live feed shows the same voltage as I get at the switch. Good so far. However, when I connect the wires from the pump to the positive and negative feed my meter shows a few milliamps then slowly drops back to zero. I think this indicates a short circuit. How can this be? I've connected the pump wires directly to a battery on several occasions and the pump runs, indicating that there isn't a short circuit.

 

I'm going to wait for Bex to arrive before doing any more but I'm curious, what's going on here?

 

For explanation.

 

If by the bit in red you mean you disconnected the wires at whatever serves as a junction box at the pump end of the wring and then connected your meter to the wires coming out of the pump I am surprised you got ant reading unless the pump motor has a suppressor fitted. If so that reading might be normal EXCEPT it would not me milliamps when the meter is set to volts. It would be millivolts but when the meter is set to 20 volts DC it wont actually show millivolts. It will show volts to a couple of decimal places though. One thing it is not is a short circuit - possibly a bit of static but not a short.

 

If you mean you connected your meter to the whatever serves as a junction box by the pump with the pump connected to the boat's wiring then it suggest that you have a fault on the negative (return) side of the circuit much as I suggested in post 3.

 

Wait for help tomorrow.

[WotEver]

I’ve just ploughed through the entire thread.
 

I’d place good money on a faulty fuseholder. Those screw in ones are awful - the spring loses its temper and results in exactly what the OP has described. 

[Tony Brooks]

3 minutes ago, WotEver said:

I’ve just ploughed through the entire thread.
 

I’d place good money on a faulty fuseholder. Those screw in ones are awful - the spring loses its temper and results in exactly what the OP has described. 

There is good experience talking - especially if you have had a string of low battery voltages because that will up the current drawn and potentially hat up the fuse and holder.

 

From the OP's description I would be fitting a blade type fuse holder with blade type push on connection's  and spare fuse locations and blade connected switches. It may not look so posh but it will be far easier to fault find and be more reliable if the positives to the fuses are fed from a busbar rather than just a soldered cable.

[The Welsh Cruiser]

I've a feeling this low voltage thing has been going on for a while. I replaced the pump 3 years ago. A month or two after fitting it I noticed that if my battery was a bit on the low side, say 12.3 volts the pump would 'rumble' for a couple of seconds after closing a tap. The lower the voltage the longer the 'rumbling' went on for. The temporary bodge of wiring an old battery direct to the pump over the last couple of days seems to confirm this as although it's basically knackered, only showing 11.8-12 volts the pump doesn't rumble after closing a tap. This suggests to me that I've had a voltage significantly lower than this for some time, hence the struggling pump.   

[Tony Brooks]

4 minutes ago, The Welsh Cruiser said:

I've a feeling this low voltage thing has been going on for a while. I replaced the pump 3 years ago. A month or two after fitting it I noticed that if my battery was a bit on the low side, say 12.3 volts the pump would 'rumble' for a couple of seconds after closing a tap. The lower the voltage the longer the 'rumbling' went on for. The temporary bodge of wiring an old battery direct to the pump over the last couple of days seems to confirm this as although it's basically knackered, only showing 11.8-12 volts the pump doesn't rumble after closing a tap. This suggests to me that I've had a voltage significantly lower than this for some time, hence the struggling pump.   

In view of that it is likely to indicate undersized wiring to the pump, both positive and negtaive but see how it goes once you have cured the fault. A bad connection in the fuse holder or anywhere else would also give low voltage symptoms.

[The Welsh Cruiser]

1 hour ago, Tony Brooks said:

In view of that it is likely to indicate undersized wiring to the pump, both positive and negtaive but see how it goes once you have cured the fault. A bad connection in the fuse holder or anywhere else would also give low voltage symptoms.

The wire does seem fairly thin, given that it runs around 20 feet and the pump draws 6 amps. Having said that the previous pump didn't rumble at all. This leads me to it being linked to the issue I'm having now but who knows, maybe the 2 pumps, same brand and model, have different characteristics.

[Tony Brooks]

40 minutes ago, The Welsh Cruiser said:

The wire does seem fairly thin, given that it runs around 20 feet and the pump draws 6 amps. Having said that the previous pump didn't rumble at all. This leads me to it being linked to the issue I'm having now but who knows, maybe the 2 pumps, same brand and model, have different characteristics.

If the inlet strainer becomes blocked water pumps can become noisy.

[The Welsh Cruiser]

3 minutes ago, Tony Brooks said:

If the inlet strainer becomes blocked water pumps can become noisy.

Sorry perhaps rumble wasn't the best description. What I mean is that the pump continues to run for some seconds after the tap is closed.

[Tony Brooks]

Just now, The Welsh Cruiser said:

Sorry perhaps rumble wasn't the best description. What I mean is that the pump continues to run for some seconds after the tap is closed.

That is normal to some degree, esecially if you have an accumulator but it is likely to be for longer if the voltage is down or the inlet strainer is blocked.

 

Now we learn about this I would suggest checking the inlet strainer to ensure it is clean before tomorrow's sort out. A blocked inlet strainer may also caused excess current draw.

[The Welsh Cruiser]

5 minutes ago, Tony Brooks said:

That is normal to some degree, esecially if you have an accumulator but it is likely to be for longer if the voltage is down or the inlet strainer is blocked.

 

Now we learn about this I would suggest checking the inlet strainer to ensure it is clean before tomorrow's sort out. A blocked inlet strainer may also caused excess current draw.

Thanks, I'll do that. I don't have an accumulator.

[ditchcrawler]

21 minutes ago, The Welsh Cruiser said:

Thanks, I'll do that. I don't have an accumulator.

That will also increase current draw as you will be doing more starts

[The Welsh Cruiser]

Water pump up and running again. A simple fix, but not easy to find! Bex established that the switch and fuse holder were ok. So the problem was the cable between the switch and the pump. Much of this is under the floor so we discussed the prospect of replacing the cable, not great! Almost as an afterthought we checked behind the fridge, found a joint in the cable there. Bex did her magic there (continuity test by wrapping both ends of wire together at one end, probes on the 2 wires at the other, brilliant!), established was that the fault was simply this joint, one of those horrible scotchjoin things are whatever they are called.

 

Bex was great, really friendly and helpful. 

[Tony Brooks]

Well done Bex & pleased you are sorted.

[Sir Nibble]

Scotchloks! Horrible things. Blue one where it should have been red?

[The Welsh Cruiser]

Yes a blue one, don't know if it should have been red! There are half a dozen of them around the fuse panel, I shall be replacing them!

[Dr Bob]

Yes, well done Bex.