I have an old Montgomery Wards air compressor that I bought new in the late 70"s. I replaced the pressure switch and it hasn't worked right since. It will build up pressure, shut off at about 100 lbs(as it should), then, as the pressure decreases, instead of automatically starting up, it will try to start and trip a circuit breaker. I replaced the switch once before, a few years ago. Now, I can't find the same replacement switch. I don't know who made the compressors for Wards. A person once told me the compressor was trying to start with "head pressure" on it. I think He was right, but don't know how to fix it.
It is a 1 hp. 110 max. pressure 5.4 scfm single cylinder. The Wards model # is EXR6474. I have tried Wards web sites looking for parts, but all I get is appliance repair. I have tried air compressor web sites and they say they don't carry wards replacement parts (dah)
Does anyone have any suggestions? thanks in advance, You guys always come thru for me!

 

I have see some P/S with a unloader , when the air comp. stops the unloader opens a line to the cly head so it is not starting on comppreson. was there a line going to the head or dischage sid on the old P/S?

 

Right after it builds up pressure and shuts off, do you hear it go pssssss?

I have the same vintage compressor by Sears and it was made by DeVilbiss, it uses a Pumptrol switch. I bet it's either a DeVilbiss or Campbell Hausfield.

Barry

 

I will try this for the forth time---I keep getting a message that I am not logged on( I should be, unles higher powers took me off) Cliford, my compressore doesn't have a line. I know what you mean. I have looked at the newer compressors and most have a line from the switch to the tank, mine doesn't

BB- my compressor used to do the pssss thing after it cut off, now (with the new switch)it doesn't
I think I just need the proper switch(which I can't find)
I just e-mailed a couple of web sites that sell furnas parts, but i am having problems with the forms saying it is a bad #. The # on the old switch is plain as day, but probably is an old #

AS always any help is greatly appreciated!

 

Okay, I've got to ask these questions-I'm sure it's dumb, but I'll ask anyway. 1)Does it trip your home circuit breaker or one on the aircompressor assembly? 2)Do you have the right amperage circuit breaker installed for that air compressor?

The best way to get the current switch part number is to contact the switch manufacturer, if they are still in business. The next best way is to contact a large electrical supply house, ie. Grainger, and see if they can cross reference the part numbers to another switch.

 

hey Ron , the circuit breaker is a 30 amp. probably a little bigger than it should be, and the recepticle is just below the breaker box, so there is on significant line loss.
I will try grainger - I haven't tried them yet . Thanks!

 

You can pick up an pressure cutoff switch with unloader valve at any good tool supply store. You just need to know your motor HP and voltage. I think I have even seen them at the local Home Depot.

 

Thanks torque1st - The unloader valve must be the key. I have tried several places locally to find an exact replacement part, but the nearest GOOD tool suppy store is 100 miles from me (including home depot). I have e-mailed Grainger (as suggested in this forum) and am waiting for their reply, they should have it.

 

I ordered and recieved a new pressure switch with an unloader valve. I installed it and I have the same problem-- The compressor starts, runs fine,cuts off at the proper PSI (110 lbs), BUT it doesn't go pssss, and the compressor will not come on at the cut-in pressure. The compressor motor trys to start, but tripps a breaker.
From reading everyones posts, I think the motor is trying to start under pressure and can't start. After I bleed the pressure off and reset the breaker, it starts and runs again to the cut-out point. HOW DO I GET IT TO GO PSSSS, like it used to do ?

 

I am answering my own post, just in case someone else has the same problems with their 30 year old wards compressor. After changing the pressure switch, with no results, I removed the check valve. I gave it a thorogh cleaning, the tiny orifice in it was plugged. Installed it and now it runs like a charm, cutting in and out when it is supposed to.

 

Cleaning that valve first would have saved you a lot of trouble. You did not mention that you had the problem before the replacement of the pressure valve. You said it happened AFTER the replacement of the pressure control. -Another case of missing or not enuf information.

 

I have actually replaced the valve twice. I thought that I had purchased the wrong pressure valve the first time, so I bought the second, making sure it had an unloader valve( the first one probably had an unloader valve too, but I don't know what it looks like.) It doesn't matter! All that matters to me is that I didn't need to buy another compressor. Thanks!

 

Hehe, that is the big thing!

I have another compressor going together from parts for my shop. It is an interesting 2 cylinder single stage compressor that has unloader valves in the head so that the motor runs continually if needed for high volume applications and the compressor itself cycles on and off. I can also set it with a switch so that it runs like your compressor where the motor goes on and off also. It will be running off of a 2hp industrial motor, probably equivalent to a 5-7hp consumer model motor. When I get that one done I will probably give my old compressor to a young man I know that is just starting out in the auto shop world.

On a control with an unloader there are two pressure connections, one to sense the air pressure in the tank, and another that does the "unloader" function that vents the air in the compressor head.

 

Eric- Sounds like you will have a great compressor! There must be many different configurations of air compressors. I noticed you mentioned your 2hp industrial motor was about equivalent to a 5 hp consumer motor. I also have a 2 yr. old 5 hp Sears compressor. My 1 hp 30 year old Wards compressor will do the same job the Sears does, except it does it quieter. I guess I'm getting too old, because I always thought 5 hp meant 5 hp- not so today! My 2yr old Sears is starting to make a different noise , so Its probably about shot. Haven't had much luck with Sears lately. They just don't makem like they used to!

 

There are some threads here on air compressors that go thru the HP ratings and how the consumer is getting ...

Your old sears was probably rated with real HP not some fake instantaneous torque x Rpm type figure that has no relation to the real world off doing work.

Is your new Sears unit an integral type unit with the motor connected directly to the compressor instead of being driven by a belt? They sometimes refer to those compressors as "oilless" types. They are noisy and have a very short life.