Cheap compressor issue

nj pheonix

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I was reading a zombie drill press thread this morning and almost piled on. Being how this is only distantly related , but recently on my mind , I decided to open a new thread.
I have a cheap harbor freight compressor.
If it's not exactly this one
https://m.harborfreight.com/8-gal-2-hp-125-psi-oil-lube-air-compressor-68740.html
(It's several years old)
Here's the deal.
(Yes it has oil)
Empty (No air)
Comes on runs fine up to pressure , shuts off.
Ok so far.
Now use, drops pressure to whatever the set point is , turns on, runs slow for a cycle or two (revolutions of motor) then trips thermal.
If I reset thermal, it repeats the fail.
If I drain down air to zero.
It runs fine to full.
Truth be told, IIRC it did this since new. It did what i needed when I needed.
I meant to exchange, but let it go and it's well out of warranty now.
I just started thinking about this the other day.
I had to put air in tire and has it out.
My first Thought is maybe a start/run cap.
I have to see if it has one.
Anybody have any thoughts.
This is not a pressing issue (it's a roundtoit)
Thanks in advance
 
Make sure bleeder is dropping to re start pressure, if the comps gauge is after the switch, it will only read pressure in hose... Bleed it manually (check pressure with known good gauge), and see if it starts at full speed... Could be a start cap...
 
At first I thought the cap idea was bogus but come to think of it, when it's empty there is no load on the motor so it would start even with a weak or failing cap. If there is some pressure there is resistance to the motor and if the cap is shot it is trying to run without that extra boost. Lots of cheap caps these days. My wife bought a cheap floor fan and it lasted one season and crapped out. Bulging 4 uf motor run cap. I stuck in one I salvaged out of a dehumidifier and it works great now.
 
"Have you tried turning it off and back on again?" :p
funnily enough it works with mine sometimes . mine does have a habit of switching itself back on if i dont unplug it . then its pot luck whether it starts up and stops when full or stalls through low power issue . its not easy living with a long line issue .
 
If there is some pressure there is resistance to the motor and if the cap is shot it is trying to run without that extra boost.

Most compressors have an unloader that won't let it compress air until the motor is up to speed. Don;t know about those cheap compressors.
 
think that happens in the box with power on/off switch . or it is supposed to do so . mine will switch itself on sometimes even when i pull the plug .
 
Most compressors have an unloader that won't let it compress air until the motor is up to speed. Don;t know about those cheap compressors.
Could be. Here's mine, the unloader is that brass widget right on top of the head. Should bleed a little air out when the compressor starts.

Murray

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I likely won't get into it until the weekend.
I will say power cycling doesn't help.
I wasn't aware of the unloader. That would make sense as well.
I appreciate all the,ideas. Thanks!
 
I didn't see the size or electrical rating of the compressor here, but wondering if you're trying to use it with a long extension cord? That can make for all sorts of weirdness with voltage drop and all, throwing off the safety systems.
 
I had used a long cord.
Originally I was using to blow out sprinkler lines.
I try short cording it to wall and see if it misbehaves
I'm sure cord wouldn't be more than 50' and it was 16ga.
I also tend to have good power (122-123) so I'd tend to doubt that. I'm open minded .
I have a oilless pancake compressor that works flawlessly so unless I need more pressure or air volume I usually leave this one be.
 
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