Compressor stalls around 35 psi and then fuses blow.

by Ted
(Canada)

Compressor will run from 0 psi fine with the air release open. Once the compressor pressurizes the motor struggles, hums and seizes to run and either the fuse at the panel or internal compressor fuse blows. If I release the pressure the motor will run again until it reaches 35 psi and then seizes again. I've checked the check valve and all looks good. Its a campbell hausefeld, 4 gallon, oil compressor that is occasionally used and is only 2-3 years old. I'm thinking it may be a motor problem and therefore is it worth fixing?

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Bill says...

This doesn't sound like a pressure switch issue to me, though it might still be.

What is the normal cut in pressure... 70-90 PSI range?

Since your compressor is starting from zero PSI, the pressure switch has closed on low pressure cut in, and electricity flows to the motor through the closed pressure switch.

As the pressure rises, the pressure switch sees that pressure. When it's working properly, the pressure will rise past the pressure switch cut in level (not affecting the switch) and when the tank pressure reaches the pressure switch cut out level, the pressure switch opens, this stops the motor, and usually opens the unloader valve.

Still, if the motor is stalling at low pressure, it's more likely that the increasing load from the pressure in the tank is forcing the motor to work harder, and the motor can't handle the additional load, draws more amperage and pops the breaker, or overheats and goes of on thermal overload.

Possibly the pressure switch (cheapest fix at around $30), but more likely either something in the pump is failing increasing motor load, or motor itself is fading.

Call your local electric motor rebuilder and ask what it costs to a) check your compressor motor, b) fix the motor if it's fixable, and then you decide if it's better to do that, or get a newer unit.

Cheers,

Bill