Tools, Sharpening and Power Machinery - Air compressor shut off problem, and questions

I picked up a Husky 15 gal air compressor (WL651003AJ) at a garage sale for $25. The on/off switch was broken, but it ran when the contacts were made. So I put a new 20A toggle switch on it. It starts up, but shuts off after reaching 60-70 psi. I can run it down to empty and it won't kick back on. Even after it's empty, it doesn't always turn back on right away.

Here's a pic:
http://i264.photobucket.com/albums/ii168/linex82/compressor-parts.jpg

Questions: A... is this toggle switch OK to use? It just seemed like a simple contact was being made between these two wires, so I didn't see why not. It behaved the same without this switch installed by touching the leaf connectors together.

I looked through the FAQ and previous posts, but didn't see this exact problem. And I am new to air compressors, but could it be the regulator or check valve? Since pictures really help and I don't have a manual, can you identify B through E in the pic?

Thanks a bunch.

No, you need to have a pressure switch installed. The toggle switch has no way of telling when the unit is properly pressurized, nor when it needs air. These switches are readily available at most hardware stores.
"B" is your outlet pressure regulator. The tank may build up 125 psi, but your tools don't need but 90 psi, so you regulate it. The gauge next to it indicates the outlet pressure, but will only do so accurately when the line is dead ended. It will read tank pressure otherwise.
"C" is your tank pressure gauge.
"D" is your overpressurization pop off valve. It will pop off if the air pressure exceeds what the tank is set to handle.
"E" is the air line from the compressor head to the tank. It will get hot, so be careful.
While we're at it, you need to use this thing in an enclosure or some other protected area, since you don't have the cover for it. Things can get caught in the belt and in the motor area, making for a frowny day.

No, you need to have a pressure switch installed. The toggle switch has no way of telling when the unit is properly pressurized, nor when it needs air. These switches are readily available at most hardware stores.

From what I could tell, all the plastic switch did was force contact between two sets of metal contacts. It was just a plastic knob with a bump on it. Both contacts were labeled "motor". With the plastic switch broken, they could both be put in the ON position by manually pushing them. By putting that toggle on one of them, I am able to turn it on/off. (and even when I didn't use my switch and just manually connected the contacts, it behaved the same). Unless I am missing something with the purpose of that switch. Maybe I can look at it more closely.

"B" is your outlet pressure regulator. The tank may build up 125 psi, but your tools don't need but 90 psi, so you regulate it. The gauge next to it indicates the outlet pressure, but will only do so accurately when the line is dead ended. It will read tank pressure otherwise.
"C" is your tank pressure gauge.
"D" is your overpressurization pop off valve. It will pop off if the air pressure exceeds what the tank is set to handle.
"E" is the air line from the compressor head to the tank. It will get hot, so be careful.

Cool, thanks. I was hoping one of those contained some kind of pressure release valve of some sort... seems like something is shutting down the motor prematurely, and I was thinking there was some such valve that could be malfunctioning.

While we're at it, you need to use this thing in an enclosure or some other protected area, since you don't have the cover for it. Things can get caught in the belt and in the motor area, making for a frowny day.
Oh, there's a cover (you can see it off to the right) .. but with it on, the picture made much less sense. :)

I think to the left of the popoff valve (D) is the high/low pressure switch. You can see some kind of spring loaded tower there. If there's 2 screws or nuts on the end of the spring axis, one is for set pressure and the other for differential. It could be out of adjustment or just plain shot.
It doesnt look like the 'standard' tank pressure switches, so you might want to fab up something coming out of the tank with brass T's to fit a standard pressure switch (cheap, like $20), along with your tank pressure gauge and that popoff valve. Then fit your line regulator to it. While you're at it, change out that popoff valve too, they do get corroded with time.. if your pressure switch contacts get stuck on and the compressor is able to exceed your tank pressure, you could have a situation. Some come preset, some you have to adjust.

Well duh, I should have thought you would have a cover for it, just wasn't thinking straight. The toggle switch does not manually move the contactors. Air pressure coming from a pitot tube below actuates the lever and causes the contactors to engage with low pressure and disengage when high pressure is attained. You have a dead switch, and the compressor doesn't know when to come on if you have bypassed the contactors. This is the reason it isn't coming on when you reach a low pressure point. The switch is about $10, still within the realm of a good deal considering you stole the compressor in the first place!
Some suppliers charge more for their parts, but here's what you are looking for Grainger Industrial Supply (http://www.grainger.com/Grainger/wwg/productIndex.shtml?operator=prodIndexRefinementSearch&originalValue=compressor+switch&L1=Compressor)

ok, here's another pic...

http://i264.photobucket.com/albums/ii168/linex82/compressor-overhead.jpg

upper right: my awesome rendering of the on/off toggle that was there but not working. basically the flimsy plastic piece that connected it to the tension switch was broken. The blade connectors for B1 and B2 are what I connected to my toggle. You can see the contact point for them. I thought that if W1 and W2 were connected, this would work... but I didn't account for the pressure shutoff. The spring loaded switch (you can't see) contacts B1/B2 and W1/W2 at the same time as far as I can tell.

Now what is the thing I've labeled ??. It runs to where the air goes into the tank. By the nature of where it is, it seems like some kind of pressure sensor. Remember, it's only getting up to about 60 psi then shutting off... so something is telling it to do that. I don't think my switch is my main problem. But I could be wrong, that's why I'm asking. :)

Oh, and both gauges read the same, and my pressure regulator is turned all the way up. I think if I had a manual this would be a piece of cake.

OK, you have a pressure switch in place. Not too clear on the first pix. It is adjustable, but you will have to find that adjustment point to increase tank pressure. The thing you have marked is the pitot tube, that runs pressure from the tank to the switch to tell it about the condition of the air pressure. Both gauges will read the same until you dead end the hose. Basically let the air flow freely out the hose end, then adjust the outlet pressure with the knob. Do it quickly as you will run out of air soon. Let us know if you find that adjustment point.

I wanted to eliminate the switch as the problem. So I removed the black and white wires from the pressure switch. I wired the black to black and white to white - effectively hard-wiring the motor it to "ON".

Plugged it in, watched the pressure get up to 65 lbs, then it shut off.

So this is telling me my switch isn't shutting it down. Help me understand what could be shutting it off. If I hard-wired it ON like that, shouldn't it just run until I pull the plug? The only other wire is the one to ground.

You bypassed the pressure switch and it still shut down by itself? Hmm.. Short of thermal overload, nothing comes to mind, but ar 65 psi? Very strange. By the way, the black tube you traced out in your second pic is the unloader line. The switch has a direct npt connection to the tank on the bottom.

If you blow some air out of the line as its building up to 65.. does it still hit 65 ?

IM just wondering if the 65 is pressure related or motor-time related.

Im still going with change the pressure switch though.. :)

If you blow some air out of the line as its building up to 65.. does it still hit 65 ?

IM just wondering if the 65 is pressure related or motor-time related.

Im still going with change the pressure switch though.. :)

Good idea. I tried this - I kept blowing off the air as it was filling... did it several times in fact... once it hit 60, it stopped.

Then I went and mowed the yard, came back, and plugged it in again... it filled it to 80. I waited a little while longer, tried it again, and it filled to 105.

So now I am really confused. Shuts off at around 60, then 80, then 105. It won't kick back on on its own. I have it hard-wired on, so it isn't the pressure switch.

Any ideas?

Sounds like either the motor is tired or dirty and overheating to trip, or the compressor side worn and making the motor work harder than it should .. shutting it down on an overheat/overcurrent. I suppose its possible the overheat/current trip sensor is funky.

If you have an amp-clamp, you can check the current draw on the motor as it runs that cycle. There should be a plate on the motor showing how many amps are typical. Dont use a regular VOM amp connection, they typically top out at 1amp or so.. that motor probably draws quite a bit more.

Look thru the motor vent slots with a flashlight, is it all full of gunky dust in there ?