Trouble shooting wiring - advice please.

[Simi 60]

Woke this morning to no water coming from taps, figured it was another 24v pump dead.
We tend to go through one every 12 to 18 mths so have a spare on hand

Old one out, new on in, no go.

Multimeter on wires and there's 25+ volt there
Takes old pump into ER and connect up to 24v start battery and the old pump lives.

Back to where the pump was installed and again, 25+v at the wires, but pump no go.
Scratches head - what's going on?
I am guessing somewhere in the wires there is a break or bad connection allowing voltage reading but no actual amps flowing?
Have I described that right?


Installs a 240v AC pressure pump and we are away again but I still wouldn't mind knowing why 25v+DC is not running the pumps

[SV_FlyingTigress]

First clean the connections of the power and ground at the pump.-you probably did that, but if not do it and see if it runs...if not then remove, clean and reinstall the positive and ground connections at the source ends (probably the switch for the power and some buss bar for the ground). If that fix things, great, if not then if there is a way to externally connect a *known good* ground jumper wire and run it to the pump and replace the ground on the pump with the known good jumper ground and see if the pump all the sudden works. If it does the ground wire is compromised with a bad connection; run a new wire or troubleshoot the existing one. If it doesn't work, try running a jumper positive 24v *power* jumper wire in the same manner and replace the power wire and see if that helps. That will tell you if the bad connection is on the power or ground side. You can measure correct voltage but if you have a bad ground it won't allow enough amps through to run the pump...same with a poorly connected power wire. Poor connections can be corrosion or wire breakage at the connector to terminal or at the wire to connector junction or in the middle of the wire. If you have a DC wiring problem, it is probably covered above.

[Simi 60]

Thanks and what I was thinking and would have got to eventually.

[SV_FlyingTigress]

Order this and put it on all your new electrical connections that you make (wire to connector crimp or connector to terminal) or old ones that you disconnect and clean. Very unlikely to get oxidation there in the near future:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Simi 60]

Thanks, I used ox gard (same same but different) and tinned copper on my end down to the bus bars when I did the install several years ago.
Has to be original wiring running internally that has the issue.

Depending on ease of access to wire I may decide to not worry about the 24v pumps and stick with the 240v pump as I had bought it with the intention of scrapping the unreliable 24v pumps a year ago.
We have gone through 5 in 6 years
1 Johnson and 4 Vetus


New hopefully more robust Big Bertha below

[SailingHarmonie]

Originally Posted by Simi 60

Woke this morning to no water coming from taps, figured it was another 24v pump dead.
We tend to go through one every 12 to 18 mths so have a spare on hand

Aside from your current wiring issue, why do you tolerate such crappy pumps? They are designed for people who use their boats once a month for a few hours, not for 24/7/365 liveaboard service.

I learned many sea miles ago that the lifespan of cheap potable water pumps just doesn't make up for the frustrations for short lifespans and deaths at very inconvenient times. Usually just after you have soaped up in the shower but before you have had a chance to rinse off...

Spend a little more money, get decent pumps. Live better.

Groco PJR are awesome, and really expensive. Your grandchildren will inherit them.

Marcos are a good deal less expensive but really reliable. Change the shaft seal once a year, and they will go forever.

[mglomstead]

Had the same symptoms with a radio - had voltage, but not enough juice to light up the radio. Traced the issue to a bad connection on one end of an inline fuse. You may have a bad connection some where.

[Simi 60]

Originally Posted by SailingHarmonie

Aside from your current wiring issue, why do you tolerate such crappy pumps? They are designed for people who use their boats once a month for a few hours, not for 24/7/365 liveaboard service.

I learned many sea miles ago that the lifespan of cheap potable water pumps just doesn't make up for the frustrations for short lifespans and deaths at very inconvenient times. Usually just after you have soaped up in the shower but before you have had a chance to rinse off...

Spend a little more money, get decent pumps. Live better.

Groco PJR are awesome, and really expensive. Your grandchildren will inherit them.

Marcos are a good deal less expensive but really reliable. Change the shaft seal once a year, and they will go forever.

The Vetus have a 3 year warranty and crap out in less than that so I have only bought one
Where I have the pumps set up takes all of 10 minutes to change them out

And I have no kids let alone grand kids so seems pretty silly dropping near $6000 (Australia) on a pump
https://www.marinedirect.com.au/psr-...ressure-system

I hope the continuous rated 240v pump that cost $150 delivered will have a longer life.
It to will take no more than 10 minutes to swap out.

[smac999]

get another device to hook up and then measure the voltage. like a 24v non led lightbulb. see if it turns on. it'll be hard to measure voltage drop on the pump if it never turns on in the first place.

but yes, you can have 25v with no load, and then no volts with a load. from bad connections ect

[Bobby Lex]

Sometimes just running new wires to the device is easier and quicker than trying to find a fault in the existing wiring.

Bob

[noelex 77]

You need to measure the voltage under load. In this case that means measuring the voltage at the pump with the pump running, or trying to run.

With a high resistance connection somewhere in the wiring (which is the fault in this case) the voltage will read normally (25v) until the pump is engaged. As soon as the pump tries to draw current, the voltage will collapse to a low level and the pump will not function.

If there is any doubt about the battery, the voltage can be checked at the battery in the same way. If the battery is good, the voltage at the battery end will not collapse in the same way it does at the pump.

This collapse of the voltage under load at the supply end and not at the battery end is pathognomonic of a bad connection.

[Scorpius]

Originally Posted by Simi 60

Woke this morning to no water coming from taps, figured it was another 24v pump dead.
We tend to go through one every 12 to 18 mths so have a spare on hand

My gawd, that's eating a lot of pumps! I'm just installed my third pump. The first one was not new when I bought the boat 38 years ago. That pump died a natural death after 20 or so years. The second one lasted until it froze last winter (my bad!). And it's only a 12v system!

Perhaps you've been going through so many pumps because you've had bad wiring or connections all this time and the pumps have been running on MUCH less than 24V.

[wholybee]

Maybe I am lucky. All of my cheap pumps from West Marine lasted through my 5 year circumnavigation and are still going. If I had one fail every 18 months I would be looking for something else wrong to cause it. Certainly, change brands. I see no reason for a pump to be expensive to last.

[Bycrick]

Using a digital voltmeter to debug circuits will quite often lead you down this rabbit hole where you can waste lots of time and money. A DVM draws almost no current when measuring. Hence a "bad" connection that will only allow micro amps to flow will read as just fine. Debugging is easier with an old-fashioned incandescent test light bulb. It will draw enough current to show most bad connections and wires.