Pond Boss Forums AERATION Systems questions Problem with Gast pump

I have two Gast 1/3 HP double piston pumps I bought fromTed Lea several years ago ( may he rest in peace.) they both have run pretty much 24/7 for 8 months out of the year for several years now. With the exception of keeping the air filters cleaned, they have required very little maintenance.

Yesterday, I went out to clean the air filters and noticed one of the pumps wasn't running but had a very low level humming noise. So low it was very difficult to hear even with the other pump off. Obviously, with the other pump running, it hadn't kicked the circuit breaker and I'm not really sure how long it had been in this condition. I thought maybe it was the capacitor/solenoid that hangs on the side of the pump (not really sure what it's called) so I swapped out the one from the pump that runs to the one that doesn't and it still wouldn't kick on.

Again, when it's plugged in, you don't hear a click but just a real soft hum and it's not in any kind of overload because it doesn't kick the breaker or even get hot to the touch.

Any ideas on possible causes and fixes would be greatly appreciated.

Warmest Regards to all,
Paul

Will the motor rotate by hand? Also, what is the model #.

It's a Gast 1/3 HP dual piston model number 75R. I can't see how to get to the motor shaft without taking one of the two end plates off...haven't done that yet

JKB is on the right advice. Take both of the end fan guards off and see if you can turn both of the fan blades. If they turn fairly freely then it is likely a start switch/electrical problem. If the blades don't easily turn then you have something bound up in the piston heads. It may need a rebuilding of the internal 'cups'. Worst case it is a bad motor bearing.

It may also be a bad capacitor. We see that problem often. Most multimeters has a capacitance function. Make sure you unhook the capacitor prior to checking its capacitance. You probably have a 15uF capacitor. Or take the one off the running pump and put it on the non-running pump and see if it starts working.

Shawn! Where the heck have you been hiding? Good to see you posting again.

That is the same model I have here. The motor is a PSC (Permanent Split Capacitor) motor. Good motors, but have very low starting torque. You swapped the capacitor, so it would be more likely that something is binding it up, like Bill said. These motors do not have an internal switch, so you won't hear a click when they start.

Shaft was locked pretty tight. Was able to free it. It turned freely by hand. Plug it in and it ran for about a half second and locked up again. Freed by hand again, ran again and same thing happened. Am thinking something is jamming it up in one or both cylinders.

Bill, should I just go the rebuild rout eat this point?

Thanks to all for your comments/suggestions.

I suspect one of the rubber cups is broken/cracked and causing the binding or locking up. I think a rebuild should be investigated. There are instructions here and on line of how to rebuild those pumps. Sprkplug a member here does rebuilding of those pumps. Here is some additional information. Sprkplug and I have rebuild kits available for those GAST pumps. The rebuild procedure for Gast and Thomas rocking piston compressors are similar.
https://www.youtube.com/watch?v=JvVv2iRDVz8
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=390615

[quote=
Bill, should I just go the rebuild rout eat this point?

Thanks to all for your comments/suggestions.[/quote]

Rebuild sounds in order but DONT eat it what ever you do!! LOL Just kidding....

Your apparent mechanical failure is one that I have not thought much about with the 75R... yet.

From my perspective, and the possibility of being remote with the compressor. It would be fairly easy to add a Zero Speed Switch to detect if the motor is rotating after turning it on.



Just pick-up the bottom of the rod with a proximity switch every time the motor makes a revolution. Can also get RPM this way.

Just another thing for diagnostics tho.

I agree with Bill in that a cylinder/piston issue is a strong possibility. I had a Thomas snap off the screw that holds the top half of the piston to the conn rod. You could hear the racket over the engine noise of the Kawasaki mule while driving up. Maybe something on top of a piston also, that jams up the works at TDC....not much clearance in there.

Whatever the reason, dis-assembly is in order.

FWIW I bought a pump rebuild kit for my 75R from Bill C. when I was buying an inlet filter upgrade kit he designed. Figured a reasonably priced pump rebuild kit would be nice to have on hand should the need arise. I suspect Sparkie can hook you up with some reasonably priced items to have on hand as well.

Thanks all for your comments. Bill squared me away.

Have a great 4th!

Finding this thread on a google search, I have the same Gast 1/3hp pump (model 75R) as Freedomeagle and now having the same problem.

The motor won't start, it just hums.

I just rebuilt the pump several weeks ago with new cylinders, cups, gaskets, etc., and it was running like new. Then Monday morning went out to the pond to find the pump only humming, and warm. And this was after 4" of rain in 2 hours along with high winds Sunday night yet the inside of the cabinet was dry).

The fan blades spin freely so it's leading me to the capacitor. But not having a capacitance tester, I only have a digital and analog mulitmeter.

The rating on the capacitor is 10uf, 440VAC

On the digital one set to Ohms I get no reaction (although on the tester it shows the Ohm symbol to 250V, my capacitor shows 440VAC), it just stays on "OL". On the analog tester set to "Ohm X1k" (only setting), when I touch the contacts the dial jumps to 3 then drops back to zero very quickly. When I reverse the contacts it does the same thing. If I touch the contacts a second time, there's no reaction, only each time they're reversed.

Does anyone know of another or better way of testing the capacitor, short of finding someone with a capacitance tester?

Thanks!

Keith

Keith,

FWIW I had the same issue a couple months ago. My problem was the inlet filter was plugged with small little "worms." My advice, take your inlet filter assembly off and try again.

Bill D.

Edit: Somebody like Sparkie or JKB can give more technical advice I bet

I assume you read this post from above?.
"It may also be a bad capacitor. We see that problem often. Most multimeters has a capacitance function. Make sure you unhook the capacitor prior to checking its capacitance. You probably have a 15uF capacitor. Or take the one off the running pump and put it on the non-running pump and see if it starts working."
I found out that you can get capacitors on eBay for reasonable to low cost. A 'handy fixit man' told me you do not need a perfectly matched capacitor for most motors. Not sure if it is true, but the ill matched capacitor he loaned be worked okay until I received one from an eBay seller.

Thanks, Bill D and Mr. Cody!

The inlet filter is clear, Bill D.

I did read through the post Bill but neither of my testers have a capacitance function and I should have clarified I don't have two pumps to be able to try a different capacitor.

So I'm guessing without a capacitance tester neither of mine will test it (accurately).

I also found them on ebay from $7-$13 and was about to order one, until that part of me wouldn't until I knew if this one's bad. Unless that's a no brainer and I'm just not catching on . Which is entirely possible

Since the motor turns freely by hand, my money is on the capacitor.

Tony, did you ever find a source for parts? Didn't you have one from Cecil where the thermal switch was bad?

Cecil's unit was a rotary vane. Never did find a thermal switch, but was able to have a customer of mine take a look at it. He retired from owning an electric motor shop. His take was a short, and rather than rewind, he recommended replacement.

Maybe should add a cautionary note. Capacitors are essentially storage devices, and depending upon their application may store a pretty good charge. I tend to isolate from power, unplug the cap. with insulated pliers, and use an insulated screwdriver to short the terminals. Some can really give you a jolt.

Good cautionary note Tony. Cap's can whack you pretty good if you're not careful, but they discharge pretty quick and you don't want them discharging into you.

The 75R (I have one) has a PSC motor. There is a start winding with a capacitor and a run winding. If it just hums when you turn it on, it's most likely in the start circuit which could be the cap or start winding.

Cap's fail more frequently than winding's, but they also fail.

If the motor turns freely like spinning it with your finger, then I would discount a mechanical problem.

Thanks guys, and I'm familiar with the start and run capacitors and the charge they can hold, from a RV AC unit that I had to replace the capacitor on, and was forewarned before messing with it!

With this one being a 440V capacitor (240V pump) I wasn't about to take any chances! And I read that even crossing the terminals with a screwdriver could cause it to explode . And please don't get the impression I know what I'm talking about with this stuff, because I don't! I'm just a research junkie trying to learn .

I have a local Grainger that will have a new capacitor for me tomorrow if needed, after checking the capacitance in my old one.

My hope is that mine is bad (for a $12 fix!).

JKB, you ever charge an automotive condenser, (back in the dark ages) carry it into the auto parts store and toss it on the counter with a request for "one just like it"?

Always wanted to make sure you had a direct and clear line of travel to the door before doing so, however. Chances are there would be a partsman coming across that counter in your direction very shortly.