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Topic: Air Compressor Troubles (Read 1885 times) previous topic - next topic

Air Compressor Troubles

Reply #15 –
I don't know if ifixawata is still following this thread or not. He may have given up on us or got it fixed and didn't tell us about it.

Anyhow to recap; he has voltage to the line side of the motor control box and no voltage on the load side.
That would seem to rule out any problem with the motor or motor start capacitors.

Trouble shooting A/C circuits by measuring between wires and ground can be tricky and confusing. Unlike in a car, ground is not part of the circuit where current flows. The ground, green wire or bonding conductor is only for safety.

He states that the pressure switch has two small wires to it and and checks out with 110 volts to it. Measured from where to where?

If the switch is closed, which it should be with no air pressure, the measurement between the two wires should be 0 volts.
If the switch is open the voltage between the the two wires will be the pick coil voltage for the contactor relay.

Measuring 110 volts from each wire to ground could mean the switch is either open(bad) or closed(good)!! Huh? How could that be?

If the pick coil uses 110 volts and they run the "hot" wire through the switch to the pick coil and a nuetral wire to the other side of the pick coil, then 110 volts from each wire to ground means the switch is closed (good).

If the pick coil uses 220 volts and they run one "hot" wire through the switch to the pick coil and the other "hot" wire to the other side of the pick coil, then 110 volts to ground from each wire means the switch is open (bad).
On one wire you see the direct "hot" wire. On the other wire you see the other "hot" wire through the pick coil.


By the way the start capacitor can be used on either a 110 volt or a 220 volt motor.
Its purpose is to cause a delay or phase shift to some of the windings in the stator to get the motor started. Otherwise it may just sit there and hum depending on where the rotor stopped in relation to the stator and the load on the motor.

Three phase motors don't need any help from capacitors or seperate start windings etc.
They start naturally if you will.
The three phases are 120 degrees apart by the way.

Air Compressor Troubles

Reply #16 –
As far as I know, It's still dead.

Air Compressor Troubles

Reply #17 –
So, if you put your meter across the two wires going to the pressure switch, what have you got?
 

Air Compressor Troubles

Reply #18 –
Wow, you must be in the electrical business. I tip my hat to you and as futher acknowledgement I here by remove my posts on this subject. It's clear to me what I said was misleading. Thank you for righting the thread.