Re: Sears air compressor starting problem



Yeah: Twenty amp circuit. Seriously. Been there, done that, though not with the identical model (mine is 25 years old, give or take). Try that before you decide to spend money/time on the problem.
Jim Stuyck
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two thing come to mind the circuit cant handle the start up load of the when restarting with air in the tank. Is is in a dedicated circuit? have you tried useing a different plug on a different circuit maybe one that is closer to the service box. or the check valve has failed and or leaking keeping the pump under presuure / load making the restarting harder thus the need for more amps to restart and the circuit cant handle it.
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replace the check valve.
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Keep the whole world singing. . .
Dan G

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Hey Jim,
Why would a larger capacity circuit breaker allow a motor to start instead of stalling? I don't think so. Just lets the "stall" continue for a few more seconds.
The compressor needs to start "unloaded", and it seems to do that OK with zero pressure in the system. It seems apparent to me that the compressor unloading valve is not working when the control opens at the high pressure set-point. So it traps the high pressure air in the compressor cylinder and keeps it on BDC, thereby stalling the motor.
Take care.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXXXXXXX
wrote:

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Fellow wrote that the circuit breaker tripped. Mine did, too.
Now, if the fellow plugs his compressor into a 20-amp circuit, and that does NOT cure his problem, well and good. Nothing ventured, nothing gained. But if it DOES restart, then he's spent nothing but a few minutes.
Like I wrote, 25 years ago a 15-amp circuit, which SHOULD have been sufficient, was not. Switched to a 20-amp circuit and haven't had a problem since.
Jim Stuyck
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Brian Lawson wrote:

It's not just the breaker, it's the wiring to the outlet. The higher capacity means bigger wires, so less voltage drop in the feedwires for the same current. That gives a little more oomph when starting.
Still, the right answer is probably:

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Brian Lawson wrote:

went out and did the same thing(overloaded the motor) if it was the unloader not working even without air in the tank a defective unloader would not let the compressor start and would draw too many amps and blow the fuse or set off the circuit breaker.....
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<snip>

It COULD be either one! Some compressors are "self-unloading" and depend on the check valve to keep the pressure from coming back. Those using an unloader valve depend on BOTH. My Craftsman oilless started doing that after transporting it, found the 1/4" tube to the unloader had been bent, moving the unloader so it didn't activate when the switch shut off the motor. Result: blown breaker. Readjusted unloader bracket, it's been fine ever since.If the check valve were bleeding a little pressure back through, the unloader valve should handle keeping it bled off until startup time. Nahmie
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Does the compressor make a hissing sound when it shuts off at high pressure? If not then the unloader valve on the pressure switch is bad. My son has a PC pancake compressor that was not restarting after shutting off even though the unloader was working. The compressor was plugged in a good distance from the breaker panel and the voltage drop was too great to allow the compressor to get a good start. I solve the problem by adding a T fitting in the line going from the compressor to the tank and aconnected a piece of air hose capped on the end to the line. The extra volume allows the compressor to build up the pressure in the line before overcoming the check valve spring. Works fine. I've seen this problem alot on construction sites where compressors are often run using extension cords.
Chuck Jurgens wrote:

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No being familiar with Sears. Is this an oil or oil less?
I have an older Emglo, 15 amp, oil. From factory they put 30w oil in it, it would start up with no air in it, then do the same as what yours is doing. Hum until it would trip the breaker. Drained the oil, put in 5w30 in it, no problems for at least 8 years.
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