# Vintage Worthington air compressor



## BrandonA5454 (Jan 31, 2021)

Hello everyone,

I am in need of assistance with my air compressor. I have attached all of the information that I have been able to find on it, but I cannot find any information pertaining to the max and min RPM rating of the pump. Also, the compressor will start from 0psi and run up to 150psi then cut out just fine, however, when it gets back to the cut in pressure of 120psi the motor does not kick in at full speed. It is like it is bogging down. I know this could be due to the fact the unloader valve is not bleeding air off the piston and it is trying to start with pressure on the head. I do not know where the unloader valve is though. I have attached the 2 manuals I was sent by Worthington, and a photo of a pump just like mine I found on the inter-web. Any information anyone would be able to offer me would be greatly appreciated. I know some people may say get a new compressor, but the compressor builds pressure great and operates fine for the most part. It belonged to my late grandfather and I like fixing old stuff rather than buying new junk.

Thanks in advance.


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## iowagold (Jan 22, 2020)

how good are you with working on compressors?
yea this get down to hard core repair stuff.
make sure you have the old tank checked for rust on the inside.
so when the compressor kicks off do you hear the un loader working?

do you have a clamp meter for current?
you could also have a start switch or start cap issue...
or a too small of feed line to the compressor power.
that is often overlooked when dealing with older units as the current demand can be higher on the older units.


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## BrandonA5454 (Jan 31, 2021)

iowagold said:


> how good are you with working on compressors?
> yea this get down to hard core repair stuff.
> make sure you have the old tank checked for rust on the inside.
> so when the compressor kicks off do you hear the un loader working?
> ...


This is my first time working on a compressor, but I am a tinkerer. I can usually fix anything that breaks with a small amount of assistance needed as I need now. I have checked the tank with a bore scope. The tank seems to be free of major rust. It has rust in areas, but it is just surface rust. As for the motor, I took the brushes off last night and found that (2) of the (4) brushes had broken wires and the armature was extremely black. So, I cleaned the armature and ordered a new set of brushes which I will be receiving next week sometime. I do not hear the the compressor expel air at the end of the cycle, so I know that unloader valve is not working. I just cannot find an unloader valve on it. I changed the check valve a couple days ago thinking that was my problem, but to no avail. It did the same thing when the motor kicked back on to recover. I have a touch meter for current, but doesn't give a reading just says if it is live or not.


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## iowagold (Jan 22, 2020)

check the check valve.
make sure it is working right.

the unload-er is upper right of the white tag in the pix you posted
the power should feed in this switch then loop to the motor input.

i could not find any parts for this old unit.

i would still use an inspection camera and check the inside of the tank...
tanks can rust from the inside out...
so the outside paint can be good, and the tank can be thin on the inside.

they also make expensive metal thickness tools to check tanks..
most mfg's use xray for welds and tanks for cracks.

snap some real pix of the compressor you have.
and any tags.


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## stevon (Mar 5, 2019)

BrandonA5454,

Before I bought any parts or got more into fixing this compressor, I would "hydrostatic test" the tank (just google how to do this). If the tank passed the test I would either fix the original unloader valve or get a pressure switch that has an unloader valve built into it. You will also may also need a check valve that has an unloader port. Check valves are a maintenance item anyways and they are relatively cheap. Do you know if your old one even works? Take the old check valve to Graingers and tell them that you wish to by pass old unloader on your compressor. They should help you out with parts and advice.

Stephen



BrandonA5454 said:


> Hello everyone,
> 
> I am in need of assistance with my air compressor. I have attached all of the information that I have been able to find on it, but I cannot find any information pertaining to the max and min RPM rating of the pump. Also, the compressor will start from 0psi and run up to 150psi then cut out just fine, however, when it gets back to the cut in pressure of 120psi the motor does not kick in at full speed. It is like it is bogging down. I know this could be due to the fact the unloader valve is not bleeding air off the piston and it is trying to start with pressure on the head. I do not know where the unloader valve is though. I have attached the 2 manuals I was sent by Worthington, and a photo of a pump just like mine I found on the inter-web. Any information anyone would be able to offer me would be greatly appreciated. I know some people may say get a new compressor, but the compressor builds pressure great and operates fine for the most part. It belonged to my late grandfather and I like fixing old stuff rather than buying new junk.
> 
> Thanks in advance.


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## BrandonA5454 (Jan 31, 2021)

stevon said:


> BrandonA5454,
> 
> Before I bought any parts or got more into fixing this compressor, I would "hydrostatic test" the tank (just google how to do this). If the tank passed the test I would either fix the original unloader valve or get a pressure switch that has an unloader valve built into it. You will also may also need a check valve that has an unloader port. Check valves are a maintenance item anyways and they are relatively cheap. Do you know if your old one even works? Take the old check valve to Graingers and tell them that you wish to by pass old unloader on your compressor. They should help you out with parts and advice.
> 
> Stephen


I ended up replacing the check valve because the spring was broken inside of it. I just got a new pressure switch that has an integrated unloader valve. There isn't one on the compressor at the moment and it does not look like there has been for a while. It came from the manufacturer with a magnetic unloader valve, but I have not seen one on it since I have used the compressor. I will be hooking everything back up this evening. I took the motor apart and found that (2) of the (4) motor brushes had broken wires so i will be replacing them as well. I am confident that all of this will solve my issue as well. Also, I upped the size of the pulley on the motor to 5" and increased my RPM from 400ish to around 600ish. I am not worried about the tank at all. I inspected the tank when I had the pump off cleaning the heads. Used a bore scope to inspect all seams. Inside of the tank looks good. I have no issues with leaking air either.


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## stevon (Mar 5, 2019)

BrandonA54,

Changing the drive pulley to a larger size will change the pump rpm but also the current drawn. Motor will see more load, draw more current and heat up more. With a worn compressor you might get away with a slightly bigger pulley and lowering the cutoff pressure on the pressure shutoff switch. Pipe the port in the check valve to the new pressure switch unloader valve. Have fun!

Stephen



BrandonA5454 said:


> I ended up replacing the check valve because the spring was broken inside of it. I just got a new pressure switch that has an integrated unloader valve. There isn't one on the compressor at the moment and it does not look like there has been for a while. It came from the manufacturer with a magnetic unloader valve, but I have not seen one on it since I have used the compressor. I will be hooking everything back up this evening. I took the motor apart and found that (2) of the (4) motor brushes had broken wires so i will be replacing them as well. I am confident that all of this will solve my issue as well. Also, I upped the size of the pulley on the motor to 5" and increased my RPM from 400ish to around 600ish. I am not worried about the tank at all. I inspected the tank when I had the pump off cleaning the heads. Used a bore scope to inspect all seams. Inside of the tank looks good. I have no issues with leaking air either.


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## stevon (Mar 5, 2019)

BrandonA5454, 

A cheap clamp on ammeter does the job, for $14 bucks if I were you I'd would buy one, they are quite handy when working with electric motors.









6 Function Mini Clamp Meter


Amazing deals on this 6 Function Mini Digital Multimeter at Harbor Freight. Quality tools & low prices.




www.harborfreight.com





Stephen


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## BrandonA5454 (Jan 31, 2021)

Hello everyone,

I want to thank you all for the help. I ended up buying a pressure switch that had an unloader valve built in. Then I just plumbed over from the check valve to the switch using 1/4" high pressure hose. I bought a new motor as well. I ended up buying a Tractor Supply 6hp 3450rpm motor. I put a 3.5" pulley on the motor and the pump has a 16.5", this upped my rpms from 600ish where my old motor was turning it. This cut down on my recover time by over half. It was taking around 5 minutes to recover from 120psi to 160psi. Now it recovers in around 1 minute and a half. The compressor is still quiet and seems to run better at this speed as well. I just wanted to say thanks and give an update.

Good day.


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## stevon (Mar 5, 2019)

BrandonA5454, 

Sounds like you got things sorted, thanks for the update

Stephen


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