Blowing capacitors

I bought a house that no one has been living in for some time and it has a 1HP deep well with a control box, I don't know how deep it is or what brand motor it is.
I threw the breaker and it started to pump water for about 20-30 seconds then the control box started to smoke so I shut the breaker down. Did it again same thing but this time the cap blew. I figured it was a bad capacitor so I bought a new one, same thing started, smoke tried again worked for 30 seconds and blew. I thought a capacitor just gets the motor to start and after 20-30 seconds it would not be used but someone told me the motor must be drawing to many amps and blows the cap, does that sound right? He said there is a way of by passing the control box and getting the pump to run so I can check the amps and so forth but didn't tell me how. Does anyone know how to do this and can explain to me step by step how. I am a very handy guy and can handle it if told what to do. Could it be that the pump is just clogged up from sitting? Can it be serviced? The pressure switch is all rusty but is not stuck or the points pitted could that be it? Thank you for any help.

Usually the starting relay is stuck and blows the start cap.

Is that a run cap or a start cap that is blowing ?

If it has two caps, then the other one may be bad.

Or maybe the motor is locked up.

Or what valveman said.


Good Luck.

I think its a start capacitor. What does a run capacitor look like? All that is in the control box is a Black Capacitor and a square thing that looks like a transformer. But like I said it will start to pump water for 20 seconds then it smokes and the capacitor is done. How long is the cap in the loop until the start capacitor kicks in and where would it be? Do you know how to bypass the capacitor? Thanks

The start capacitor would normally be energized only a few seconds. I expect that square thing (passes power through the start capacitor for a limited time) is shot. I don't know if you would be better to replace the capacitor and square thing, or to just get a new control box. I don't work on wells.

You might measure the resistance of the wires to the pump after isolating them. Measure black to yellow (run winding) and red to yellow (start winding). That could be meaningful if there is some anomaly.

Regarding what an up-top run capacitor looks like-- for one thing it would be one of two capacitors in the control box.

jcamaro said:

I think its a start capacitor. What does a run capacitor look like? All that is in the control box is a Black Capacitor and a square thing that looks like a transformer. But like I said it will start to pump water for 20 seconds then it smokes and the capacitor is done. How long is the cap in the loop until the start capacitor kicks in and where would it be? Do you know how to bypass the capacitor? Thanks

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It sounds like a start cap. A run cap is normally in a metal can.

You do not want to bybass the capacitor, or your pump motor may smoke.

That Square thing may be the relay. It should not have a transformer, unless it has a electronic controller that requires low voltage.


Can You take pictures ?

The little black square thing is the starting relay. It takes the stating capacitor out of the circuit in a fraction of a second. But if the relay is bad or the pump does not come up to speed quickly, the capacitor will smoke.

The only function of the starting capacitor and starting relay is to start the pump. Starting a pump to many times or (cycling) as it is called is the reason for having problems with the start cap and relay. A bad start cap and/or relay are one of the first signs that you are cycling your pump to death.

The pump never gets a chance to cycle it blows the cap before that. I will take some pictures.

Check the connections on the relay.

The coil is pulled in by the motor current, and takes the cap out of circuit, If working properly.

If you get a new relay, get the same exact kind. The coils have different Pull-in /Drop-out voltages to match the Pump motor.

A CSV may not be a bad idea, That would depend on how you use your water, to get full benefit.

Is your replacement caps the same Value, Voltage and Current rating ? When you say "Blowing" is that explode or they just release gas and smoke ?


Good Luck.