Compressor won’t start

[racerboy]

Hi. My 60-gal air compressor tripped a fuse today and now when I reset the fuse, it tries to start, motor spins and everything, but after about 15 seconds it just trips the fuse again. It has oil and I made sure that I drained the oil. It has a ‘Reset’ button, but that doesn’t click or do anything. When I try to reset it, there is no resistance to the button.

Any suggestions on what to do? I bought compressor about 7 years ago. It doesn’t run daily. In fact, it sometimes fouled months without use.






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[930dreamer]

A run capacitor may have blown, take the wiring box cover off.

 

[Fly YX]

Deleted

 

[Davefr]

The very first thing I'd check is the unloader valve. It should fart off head pressure so the unit starts with no air pressure load. If it tries to start under a load it could throw the breaker.

 

[bjt0055]

Not sure on the voltage? Most likely the Unloader or start capacitor like the others mentioned. I like to buy them like that as it is a simple and inexpensive fix.

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[The Cobbler]

does the motor & compressor spin freely by hand?
does it do this from zero tank pressure?

 

[racerboy]

Is the unloaded valve located near the on/off switch?




Here’s the wiring box (uncovered). It’s a 230v compressor.



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[racerboy]

How do I test the unloader valve? When I pull on it it release pressure and then it seems to stick. I have to kind of twist it to make it stop. Is that normal?


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[The Cobbler]

what you're showing id the overpressure relief valve.

 

[dagofast]

The top picture is the pressure relief valve. It only pops open in case the pressure switch (your second picture) failed to shut off the compressor. It protects the tank.

 

[bjt0055]

I'm guessing that small copper line near the switch is the Unloader valve. There's a few configurations. Some pressure switches trigger the unloading valve. It takes pressure off the head after it shuts off. You should hear air come out of it after it shuts off. Usually when this happens I buy a new tank check valve and an unload valve. The parts are cheap, just need to find the correct parts. Otherwise it could be a start capacitor as it looks to be single phase 120/208? You can check the start capacitor with a volt meter that will do that. The capacitor usually has value on it and it should check out to the that value with the meter. I would read more on that or look at YouTube to see what I'm talking about. I would focus on the valves mentioned first.

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[bjt0055]

After looking more that's a champion compressor. Look online for a parts schematic using the mod #. Then you can see what we are referring to. You should be able to easily get parts since it's a champion compressor

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[sberry]

Lots of times lead is rotted and broke right off caps. Wiggle a little.

 

[racerboy]

There are also two valves on top of the head near the air cleaner.



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[racerboy]

So the valve on the left appears frozen. I’m not sure if this is an unloader valve or a pressure release valve, but I am not able to pull Orr open by pulling on the little ring. I removed it and was going to replace it, even if it’s not the root problem.

Where do I buy one of these?



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[joe_padavano]

The unloader valve is typically built into the pressure switch and will have a small diameter copper or nylon tube leading from it to the area of check valve in the pump outlet pipe.

 

[Citation]

So the valve on the left appears frozen. I’m not sure if this is an unloader valve or a pressure release valve, but I am not able to pull Orr open by pulling on the little ring. I removed it and was going to replace it, even if it’s not the root problem.

Where do I buy one of these?



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Those are pressure relief valves/blow off valves. You have two because that's a two stage compressor. Amazon or any number of places will have them as they are a generic items (do check the pressure ratings on each).

Have you checked the capacitors in the motor? It also could be the switch in the motor that changes from starting to run mode that's the issue. Basically if the pump starts up just fine, especially if the tank is already pressurized, then you aren't dealing with an unloader valve problem

 

[Citation]

BTW, have you tried pulling the belt and seeing if the motor trips the breaker with no load?

 

[anndel]

So the valve on the left appears frozen. I’m not sure if this is an unloader valve or a pressure release valve, but I am not able to pull Orr open by pulling on the little ring. I removed it and was going to replace it, even if it’s not the root problem.

Where do I buy one of these?



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Try some WD40 on it and work it loose. Check the capacitor as well.

 

[racerboy]

I don’t see a ‘valve’ where the copper tubing goes into the switch, unless it is under the wiring block.


I ordered all new pressure relief valves and will also pull the belts tomorrow to see if it starts w/o any load on it


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[bjt0055]

Where the copper line goes to the switch is likely how it unloads, often a little needle type valve. The other end would probably go to the tank check valve.

The tank check keeps the air in the tank when the compressor unloads. A bad tank check will either leak all the time out of the unloading line or if the check valve is stuck it won't allow the compressor to pump the air in the tank. If it's stuck air has no where to go and could overload the motor.

Many things could cause this. Could be electrical? I would guess not as it doesn't look old or used hard from the few pics.

The relief valves aren't causing this but good idea to replace them.

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[redmondjp]

I seriously doubt that the unloader is causing this problem. Nobody has yet pointed out that the compressor pump itself is equipped with a centrifugal unloader - that is what the cylindrical compartment is at the end of the crankshaft - it has a flywheel centrifugal mechanism that operates a small valve, which connects to the compressor head via that 1/4" copper tubing shown in the picture above.

What is also confusing is that this compressor also seems to be equipped with a second unloader valve in the pressure control switch, with a second 1/4" copper pipe which will go back to the upstream side of the tank check valve.

You can remove the belts and take everything else out of the equation but for the motor. If it still doesn't start, as stated above check the capacitors first. If they read OK then you might want to have a motor shop look at it. It typically isn't economical to repair these motors if they end up needing a rewind. If it isn't the capacitors or the centrifugal start switch at one end of the motor, then usually you are better off going for a different motor (if that is what ends up being the issue).

 

[TonyJ]

If you want a better clue on what the problem is then remove the belts and try starting it and report back. Just removing the belt first will point everyone in the right direction on helping you get it going again without all of us including yourself chasing our tails lol.


Tony

 

[The Cobbler]

I asked a few questions early on, they didn't get answered. OP is throwing parts at this compressor without a diagnose.

 

[TonyJ]

I asked a few questions early on, they didn't get answered. OP is throwing parts at this compressor without a diagnose.

Right. That’s why I suggested the removal or the belts to start figuring it out. Myself I bought a Sb clone 5hp compressor that was doing the same thing as the OP’s is doing and at first I thought the pump till I removed the belts and it still done it. Then checked the caps - good , swapped breaker -good. Took end cover off motor and found the start switch was toast and changed that for $18 and all has been well ever since.


Tony

 

[racerboy]

Hi everyone. I finally got back into the garage today. Just to see what it looks like, I disconnected the small copper line that goes into the switch box. This is what it looks like:


Is this the unloader valve?

I took off the belt/fan guard as well. I am able to turn the pulley pretty easily by hand. How do I remove the two belts?




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[Ben Buck]

How about the check valve ?

The line that goes to the tank should have a check valve installed.

If this valve goes bad it lets tank air back through the the feed line- compressor cannot over come this back pressure.

If the tank is empty- the motor will start right up and fill- once used and the preset pressure to refill is reached- it can't overcome the tank pressure already there until empty.

YMMV

I did not read all the responses !

 

[racerboy]

So I loosened the motor and slipped the belts off. I reconnected everything. When I turn on motor, it spins w/out tripping the fuse, but little wisps of smoke are coming out of the back of motor and it smells like something is burning. Does this mean the electric motor is shot?




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[racerboy]

Here’s the spec plate on the motor



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[Davefr]

So I loosened the motor and slipped the belts off. I reconnected everything. When I turn on motor, it spins w/out tripping the fuse, but little wisps of smoke are coming out of the back of motor and it smells like something is burning. Does this mean the electric motor is shot?




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That's not good. It sounds like the motor has had a hard time starting and coming up to speed. When that happens the start windings stay energized and will start to fry. The motor's centrifical switch should disengage the start windings after just a few seconds.

It could mean the motor is shot or something prevented the motor from coming up to full speed. A new motor could suffer the same fate if it tries to start under an abnormal load.

 

[dagofast]

Disconnect the power (breaker off) and remove the fan cover from the rear of the motor. Check the contacts on the centrifugal switch. Are they welded or burned? Does it have a centrifugal switch? If not, open the box on top of the motor. Does it have capacitors in there? Are they bulging or leaking oil?

If everything looks normal, turn the power back on and run the motor with the fan cover/box cover off. Now can you see where the smoke is coming from?

If it is coming from the windings, your motor will need to be rebuilt or replaced. If it is coming from the capacitors, they need to be replaced.

Baldor is a good brand of motor with parts and rebuilding available.

 

[racerboy]

I took the end caps off the motor. I didn’t see anything suspicious but I don’t really know what I’m looking at. I did start the motor and it started smoking again.






The capacitors are not leaking and nothing looks burned in the box on top of the motor. The ‘Reset’ button has no tension and it was pretty warm to the touch on the inside. Not sure that means, if anything.


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[nadogail]

Smoke leaking from the motor is a red flag. The motor might be saved but, the labor costs to remove, disassemble, dip, bake, re assemble, install and align might be more than the cost of a new motor and installation.

 

[racerboy]

Thanks. I found what I believe is the same basic motor on Amazon. Looks like it it runs a little over $300. How hard would it be to swap them? Do I need to get an electrician to come over?


BALDOR 5HP AIR COMPRESSOR ELECTRIC MOTOR, 56HZ FRAME, 3450RPM, 208/230V, SINGLE-PHASE, 7/8" SHAFT, 1.15 SERVICE FACTOR MADE IN USA https://www.amazon.com/dp/B07SNGRPP3/?tag=atomicindus08-20


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[The Cobbler]

if it's the same frame size, the same shaft size, and the same rpm it will be fairly easy . as far as needing an electrician? depends on your ability/comfort level working with electricity

 

[racerboy]

I’m pretty confident I can do the motor swap. I’ll take a look at the wiring and if I feel like I have questions that can’t be answered here,I have no problem with calling in a local electrician. I was thinking about adding one of these Big *** Fans to the shop anyway, as well as some additional lighting, so it might make sense to make the call anyway.


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[Citation]

I’m pretty confident I can do the motor swap. I’ll take a look at the wiring and if I feel like I have questions that can’t be answered here,I have no problem with calling in a local electrician. I was thinking about adding one of these Big *** Fans to the shop anyway, as well as some additional lighting, so it might make sense to make the call anyway.


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The motor swap is mostly a mechanical job. The wiring is generally easy. You might see if there is a local motor shop that could look at your motor.

 

[racerboy]

I figure I should close out this thread. I wound up purchasing a new motor for the compressor. Installation and wiring was identical to original. All is working properly again. Appreciate all the advice for forum members. I may still have the original one serviced and just put it on a shelf as a backup.


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[The Cobbler]

Great, thanks for the update

 

[Lamakocklee]

I maybe a little late, but just wanted to say thanks to racerboy...for the details of his problems with pictures.. and his resolution.

that picture of the smoking motor made my day


After seeing that I would have totally went the route you did and secure a new motor. Glad you got it all figured out.