# Air Compressor Won't start



## meteorman (Apr 3, 2012)

I have a Campbell Hausfeld electric air compressor. 7.5 hp built in 1993 that I just inherited. I have it all set up and am having trouble getting it going. I just moved it, and we had to lean it over in order to get it in and out of the truck. It's massive and heavy. I couldn't get it to start running, and fiddled with it. I ended up draining the oil from the compressor and a BUNCH drained out (like a gallon+) I am confused because it would only accept a quart when I refilled it. I'm not even sure if that is relevant to my current problem. I did get it to run and fill the 80 gallon tank up to full pressure. I then turned off the circuit, since I don't use it much. Now that I am trying to use it again- it won't start. Nothing, nada. just sits there, no noise, motor doesn't even try. 

So I checked the power supply. it's getting 230 volts at the pressure switch. The switch is engaged and sending power to the circuit breaker (built into the compressor/not on the shop panel). The breaker is not tripped, I tripped it and reset it to check if it was working and it seems to be fine. 
The motor turns easily and the compressor seems to turn over easily too. 
I'm thinking it's either the motor or the capacitor. Any idea how to check those? the Red reset button does not seem to be tripped on the motor, and I can't push it. 
This thing is overkill for me, and if I replace it, I'd get a much smaller unit, so it's not worth it to replace the motor. 
Any ideas? is it fried? Should I have a service call for it? or just ditch it?
thanks.


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## sublime2 (Mar 21, 2012)

Generally speaking, Oil filed compressors should never be laid on their side because oil can leak into areas of the motor where it shouldn't be.
They should always be kept upright.


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## meteorman (Apr 3, 2012)

Would this keep the electric motor from turning on?
Is it toast or can it be salvaged? 
I'm confused about where all the oil came from, was it WAY over full? 

thanks for the response.


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## woodworkbykirk (Sep 25, 2011)

could be the oil issue. the compressor's reset button may have tripped also. they typically have their own breaker on them to prevent burning out the motor


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## DexterII (Jul 14, 2010)

meteorman said:


> So I checked the power supply. it's getting 230 volts at the pressure switch. The switch is engaged and sending power to the circuit breaker (built into the compressor/not on the shop panel).


I am a little confused here. You have wires coming from a circuit breaker in your main panel to the pressure switch, and then to a "breaker" on the air compressor? I'm guessing, but believe that the thing you are calling a breaker is actually a magnetic starter, perhaps with a reset, and that the power should be going to this magnetic starter, and that a pair of control wires should run from the magnetic starter to the pressure switch. Do you have the manual for this air compressor, and are you sure that you have it connected properly? A 7-1/2 H.P. motor is pretty significant, especially considering that it sounds like you did not plan to incorporate a compressor this large into your shop; are your wires properly sized?


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## meteorman (Apr 3, 2012)

My mistake, the 'circuit breaker' that I referred to is actually a magnetic starter. (i guess) 
I have a 30 amp 230v dedicated circuit for the compressor. I have 12/3 romex supplying power to the compressor. 
The compressor worked like this for 19 years. I didn't change anything about the wiring on the compressor, just ran a new supply line to it in the new shop. 
Could the problem be in the magnetic starter? I don't see any visible burn marks or disconnected wires. Everything looks clean and solid. 

I don't have a manual (that I can find) I have contacted Campbell Hausfeld for a copy of the manual.

??thanks for the responses.


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## DexterII (Jul 14, 2010)

What does the motor tag say in regard to the number of amps at 230 volts? I am thinking that the full load amps, or FLA, for a 7-1/2 HP air compressor motor is closer to 40 than 30, and, regardless, it should be on something larger than 12 gauge wire; guessing here, but probably 8 gauge. Not being critical, just trying to help you get to the problem, but maybe it's a matter of 19 years on an undersized power supply having taken its toll on one or more of the components.


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## meteorman (Apr 3, 2012)

The rating on the motor is 29 amps. I may need to upgrade the wire to #10, from what I read online, 10 is required for 30 amp service.

Would this keep the motor from running at all?
Could there be a problem with the magnetic starter? How would I check it?
Capacitor? 
Should I just take the the motor into a repair shop and have it checked?


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## DexterII (Jul 14, 2010)

Please don't be offended, but I was just reading back through your post, something occurred to me, so I have to ask; how much pressure is in the tank right now? After you get the wiring upgraded, assuming that the tank pressure is down to the point that it should kick on, and that you are comfortable in doing so, I would check the voltage at the bottom of the magnetic starter, where the leads go to the motor. If you have power at that point, the problem is in the motor, and if no power at that point, the problem is in the source side, possibly the magntic starter or pressure switch, which we may be able to further diagnose, once you get to that point.


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## meteorman (Apr 3, 2012)

I am not offended by any questions. I often miss the obvious, and my understanding of this stuff is limited.
The pressure in the tank is down to around 10psi, the pressure switch is engaged and sending power through it. 
I will check the power after the magnetic starter. Thank you for your suggestion.


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## DexterII (Jul 14, 2010)

By the way, just as a matter of a quick overview, on air compressors over say 1/2 to 1 HP and up, the current draw is such that if they were to provide direct switching of the line voltage, the points of the pressure switch would burn out in fairly short order. So, typically, the magnetic starter, in addition to providing thermal protection for the motor, acts as a relay. The power ovbiously comes into the top of the magnetic starter, and goes out the bottom of the starter to the motor. In between is a contactor, contolled by a magnetic coil, or electomagnet if you will, which is powered by one leg of the 220 line coming into the starter, which in turn passes through the pressure switch. So, in addition to checking the voltage at the bottom of the magnetic starter, you should hear a "click" when that contactor is energized.


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## meteorman (Apr 3, 2012)

ok. I checked the voltage at the bottom of both legs of the magnetic starter or magnetic coils? There is power going in, but nothing coming out to the motor. So, I guess this is where the problem is. 
Could this be because of the undersized wire?


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## DexterII (Jul 14, 2010)

Don't take this as a green light to continue operating it that way, but I doubt it. Does the magnetic starter have a "reset" button? If so, press that, and try again. You said "the pressure switch is engaged and sending power through it", which I assumed to mean that you can see that the points are closed; is that correct? Did you hear the coil in the magnetic starter "click" when you turned the power on? Do you have an ohmmeter? If so, with the power off, disconnect the two wires going into the pressure switch, and check across those terminals, to make sure that you have continuity across the pressure switch.


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## DexterII (Jul 14, 2010)

Just happened to think too that since it sounds like your problem is most likely in the starter, see if there is a make and model inside of it, and post that as well.


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## meteorman (Apr 3, 2012)

Checked continuity at the pressure switch, it was fine. 

There is No click when I put power to the compressor. 
the magnetic starter is 
Square D
Class 8911
Type DP504Z
Series A

FLA 40 
240 7.5

don't see anything visibly wrong with the unit. 
don't know how to check it, but I can see that I could remove it fairly easily. As long as I got the wires back in the right spots.


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## meteorman (Apr 3, 2012)

The part number on the magnetic starter is 
ST122010AJ

It looks like I can get a replacement magnet coil (?) or whatever it's called on ebay for about $25

The whole magnetic starter is about $130ish.

Should I take this one apart to see what's going on with it?

or should I just run the #10 wire to see if that helps? if it's getting 230 volts but not enough amps, would that prevent the magnetic starter from engaging? It seems like the starter would try to engage and then trip the breaker if there was a problem with the wire being too small.


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## DexterII (Jul 14, 2010)

When I asked for the starter number, I was thinking of trying to find a schematic for it, but two things occurred to me later; there is most likely a schematic inside the enclosure, so you could check that if you wish, but, on the other hand, it did start once, and I assume that it came prewired, so, unless you took something apart for some reason, that is probably a moot point. The only thing that I can think of at this point, other than the coil, is the pressure switch. You have two wires going into the pressure switch, correct? Turn the power off, put both of those wires under one of the terminals, thereby bypassing the pressure switch, and see if it starts. Do not leave it run this way, as doing so would result in serious mechanical damage to the compressor itself, as well in potential damage to things around it, as well as personal injury. However, nothing bad should happen if you were to simply switch it on, let it run for 5-10 seconds, to see if the problem is in the pressure switch, then shut it off. If that does not pan out, then yes, I would order a coil, although you may want to remove it first, just to confirm that none of the internal wires are loose or damaged. As for the undersized wiring, I doubt it is a contributor to a bad coil, nor to it not starting, but, again, take care of that, because it is a very serious concern as far as something much more serious, like in fire.


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## DexterII (Jul 14, 2010)

DexterII said:


> You have two wires going into the pressure switch, correct? Turn the power off, put both of those wires under one of the terminals, thereby bypassing the pressure switch, and see if it starts.


Stop. I just remembered that you said you had 220 volts at the pressure switch, so, with that in mind, I assume that you have 4 wires in the pressure switch; 2 hot, probably coming from L1 and L2, and two that run back to the coil, perhaps connected to A1 and A2? If this is the case, you want to pair the wire from L1 with the one going to A1 or A2, and the one from L2 with the remaining wire going to A1 or A2. Do not pair the wires from L1 and L2, as that would obviously give you a dead short.


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## meteorman (Apr 3, 2012)

Thank you for all the help. I have decided to sell it and get a smaller unit. 
My main problem is that I have a #10 wire supplying my shop, so I'd have to rerun the whole shop wiring to be able to use this compressor. I'm thinking that a 3 or 5hp compressor will meet my needs better. 

I have determined that there is nothing wrong with the compressor, but from the manufacturer literature that i found onine, the probable issue is a wire that is too small will keep the magnetic starter from activating.
bingo


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