# well pump electrical multimeter question



## joed (Mar 13, 2005)

Two wire or three wire feed to pump. could be a bad capacitor or control box if three wire. The pump could be running on start winding and overheating.


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## tpolk (Nov 7, 2009)

2 wire


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## joed (Mar 13, 2005)

When it stops is there still voltage to it? If there is then I would say the pump is defective.


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## tpolk (Nov 7, 2009)

yes still voltage. is there a way to check continuity thru the pump by using the two wires or does it not work like that since each wire supplys juice to the motor


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## 3 legged dog (Dec 21, 2009)

Every time my well acts up, it is this pressure switch that is the problem.


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## tpolk (Nov 7, 2009)

pressure switch brand new and appears to be functioning correctly. how would i know if it wasnt?


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## Yoyizit (Jul 11, 2008)

You need to measure the current, 7A or so. A clamp-on ammeter is recommended, but you can also use a shunt. Even if your meter has a 20A AC current scale, it still may pop the meter's internal fuse, if it has one.
Post a link to your meter; maybe more performance can be squeezed out of it.


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## tpolk (Nov 7, 2009)

sorry computer illiterate for links. its a sears craftsman auto ranging digital multi meter model 82400


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## Yoyizit (Jul 11, 2008)

tpolk said:


> sorry computer illiterate for links. its a sears craftsman auto ranging digital multi meter model 82400


Can't get a pic of it, even from the Sears site. Search engines are great when they actually work. What's the lowest AC voltage range on the meter?


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## tpolk (Nov 7, 2009)

from the table in the book it shows ac voltage-range 400mV,resolution-0.1mV
v-ac, range 4v, resolution-1mV
40-400 Hz, range 40v, resolution 10mV
auto ranging,400v/700v, resolution 100mV/1v
thanks for your input once i get a handle on the use of this tool it will stick, been in construction long time so some experience with electric first time wading into meter pool


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## Yoyizit (Jul 11, 2008)

Using the pump wire itself as a shunt is kind of hard to explain, so I'd get a clamp on ammeter. It'll pay for itself the first time you successfully diagnose anything with it.

Voltage is half the story; current is what makes things happen.


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## tpolk (Nov 7, 2009)

under current it has range 4A/ resolution 1mA
range 20A/ resolution 10 mA does this have any bearing?


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## Yoyizit (Jul 11, 2008)

tpolk said:


> under current it has range 4A/ resolution 1mA
> range 20A/ resolution 10 mA does this have any bearing?


Resolving 1 mA out of 4000 mA is pretty good.

I doubt you'll get away with using the 20A scale for a 1/2 hp motor. Even good motors draw a start-up surge.


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## tpolk (Nov 7, 2009)

thanks for your input


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## Yoyizit (Jul 11, 2008)

Actually, you already have used the wire as a shunt.



tpolk said:


> I was able to check both sides of the 30amp double pole breaker and was reading 124 each leg.
> 
> checked the wire at the well and read almost exactly the same


What size wire are you using and how many feet between the breaker and your measurement point?

100' of #10 [50' for a two conductor cable] has a resistance of 0.1 ohm. 7A would drop the voltage 0.7V, so 248.0 v at your breaker would be 247.3v at your measurement point. 
If you had very long test leads you could then measure the voltage drop on one 50' conductor, and it would be 0.35v corresponding to 7A. This way is much more accurate for measuring the current draw.


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## tpolk (Nov 7, 2009)

100' of#10


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## jbfan (Jul 1, 2004)

You can read the resistance of the motor, but what good will it do you?
The pressure switch sholud be wired with the incoming wires on the two outaide contacts, and the pump wired to the two inside contacts, or it could be wired the other way around.
Turn the power off and work the pressure switch by hand to see how it works.

With a deep well pump, there is not much troubleshooting you can do if everything up top works.
If you go through the trouble of pulling it out, you may as well replace it.


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## tpolk (Nov 7, 2009)

everything new from press switch thru well pump last nov. guess i'm yanking the rascal should still be under warranty


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## 3 legged dog (Dec 21, 2009)

Do you have 240v going to the pump when it stops pumping?


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## joed (Mar 13, 2005)

Here's my thoughts. The pump runs for 3 seconds. It's not seized. 
There is still voltage on the cables to the pump when it stops running. That indicates to me one of two problems. 1. The pump is defective and cutting off on thermal overload. 2. Bad cable that is flexing with the pump torque and opening. Either one requires the pump to be pulled. Measuring the current might help. But it still going to lead to #1 if current too high or #2 if no current when pump stops.


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## 3 legged dog (Dec 21, 2009)

If you are testing the voltage on the cable to ground, then you will not 
get a proper diagnosis.


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