How to repair compressor pressure switch?

That can be a symptom of a non-functioning unloader valve. Take the cover off the switch and watch the operation of the valve, make sure the pin is being pressed down when the switch shuts off. It's possible it got tweaked when you tightened the air line fittings. If it was work fine before you changed the switch that would be the first thing to check.
 
Hmm, there is a little hole in the pressure that bleeds off until it hits low pressure to restart.
That doesn't seem right.
You may be on to something here. I'll fiddle with it.
 
i'd check the pressure switch operation to make sure the contact is being made there.

the pressure should bleed off every time the compressor stops
 
Ulma Doctor said:
the pressure should bleed off every time the compressor stops
Click to expand...
That is so the motor and compressor can start turning from stopped without a load on them. Motors do not like to start under a heavy load. That is what the air line bleed down function on shutdown is for.
 
I installed a small reservoir between the pump and the check valve on my homebuilt to give the motor a better chance of coming to speed before it was loaded. The reservoir volume was similar to the displacement of the pump so it would take several revolutions of the pump to load the pump.
 
unloader.jpg

Things to check:
When the compressor shuts off lever A should press down firmly on pin B. This bleeds the air out of the cylinder to allow restarting with no load on the piston.

Check nut C and make sure it didn't come loose when you attached the air line. If it gets loose the valve will not open.

If air comes out of this valve for more than about 5 seconds after the compressor shuts off, then your check valve ( usually located where the air line from the cylinder head enters the tank) is leaking. These can often be removed and cleaned and will work again.
 
It’s definitely the valve. I really gronked down on the plastic line fittings, probably screwed up.
It makes sense, the flywheel is way too stiff. I have pressure built up. Now I know why the motor buzzes-won’t start.
It’s 5 hp.
Thanks, I’ll check it out tonight.
 
This forum is great!
You ask a question and within minutes there are several ideas and suggestions to remedy the issue.
That's one of the many reasons why I contribute to this site.
Thank you Hobby Machinists!
 
OK, I replaced the valve, no change.
The little hole on the side of the valve where the short term release of pressure is released (when the maximum pressure is achieved) just continues to bleed off pressure. When the low pressure starts the motor it just hums because the flywheel is locked due to pressure.
Is there a check valve somewhere that may be inoperative?
Why does the new valve bleed off the whole time?
I'm about ready to go buy a new IR 2 stage, 5HP, 60 gallon tank, 230v single phase. Talk me out of it please.
 
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