Air compressor pressure switch

[Craftsman86]

http://www.homedepot.com/h_d1/N-5yc...1&keyword=air+compressor+switch&storeId=10051

Is the switch That I bought, And I tried to wire it in to my Sanborn 30 gal compressor, no luck. So I took it to my dads old Campbell Hausfield compressor wired it in the same way as before, and It kicked right over. There is a small micro line hose that runs from the tank to the bottom of the switch into a gator grip fitting. The valve the hose hooks into has a small needle protruding out of the top, and when the compressor is turned off, the switch lowers a plate on the needle draining the air from the tank. Please tell me this is an easy fix, I have 4 hours invested in the install so far and am still not willing to give up.

Now to try and direct wire the Sanborn to make sure the motor is ok, Learn how to use these switches, and order up another one. Both take the same switch.

 

[nattyTread]

If you haven't yet found the answer, that needle valve on the switch is called an unloader. Once the tank is up to pressure and the motor shuts off, the unloader valve opens and relieves air pressure from the pump pistons. This is to permit ease of startup at next cycle since the pump pistons have less resistance to overcome.

The unloader should bleed air only for a few seconds at most; on my old CH twin compressor it is probably less than a second. Any longer than that I would suspect either the unloader is plumbed wrong, or that the check valve may be inoperable.

 

[Craftsman86]

I am reading about the unloader valve, and this does seem like the issue as when the compressor is under pressure it has a hard time turning over. Would there be a one way valve where the air line coming from the pump meets the tank? On both of the compressors that I have the unloader drains the tank completely. Hopefully that valve being out didn't ruin my compressor.

 

[nattyTread]

Yes, there is probably a check valve between the pump and tank. This is a one-way valve allowing air from the pump to go into the tank, but prevents air from the tank going back through to the pump.

If you don't have a manual/diagram, see if you can find your model online here http://www.aircompressorpartsonline.com and identify the check valve.

Testing the check valve is easy; take it off, blow through both sides; air should only go in one direction.

 

[Craftsman86]

I found them at Northern for $13 thanks man that changes everything. I bet the switch from my Sanborn wasnt blown it was the check valve the entire time.

 

[Craftsman86]

Air compressor Diagnosis
1. If it leaks air out of the switch but still turns on- Check Valve
2. Only of it doesn't turn on- Switch

 

[bsaint]

Its actually critical piece in the longevity of your compressor. On some bigger models, you'll trip the heaters if you try even once to start "loaded"

 

[Craftsman86]

It all makes sence to me now, I would go as far as saying all 4 of the compressors I have owned in the last 2 years need a check valve. Fortunately I have a friend that has a craftsman compressor with a burnt out pump hopefully Sanborn compressor will fit the craftsman motor