I know I’m not in the right subsection and I don’t care. I need help and I’m not going to sit and hope a random sole wanders into the AB section as dead as it is around here.
I’ve got a basic air compressor with tank. It looks exactly the same as the one on Harbor Freight. Anyhow, I turned it on real quick to do a touch up and encounters a problem. Initially the tank filled and the motor stopped running like its supposed to. After about 10 seconds it kicked back on and continues to run. Thinking it may have been leaking air I resealed all the connections with thread tape and am still getting the problem. I hadn’t even had the chance to depress the AB. I pick it up and listen and for the life of me I can’t hear anything leaking. Sometimes I’ll turn it on and it will do the usual fill up and then wait a few seconds to start running constantly. Other times it just runs non stop from the moment I switch it on. Anyone have any ideas or suggestions?
I’m going to assume it’s an oil-less compressor. If you’ve checked every external air connection and found those to be good, then the problem is the piston inside the compressor causing leakdown. The seal around the piston has worn and gone bad, which means the pressure in the tank will leak back through there, and while it runs air is getting by the piston seal so much that the compressor can never catch up. Sounds to me like your compressor’s toast.
The larger Craftsman compressors can be rebuilt, but if yours is a Harbor Freight cheapie or similar, I wouldnt’ put good odds on finding a rebuild kit. You might try Google to see what you can find.
I’d start with Bronto’s idea; the cutoff switch may be defective, which could be a low buck fix if you have a source for a replacement, either physical or online. DP77’s idea is also good if the problem has gotten worse over time - piston wear will cause a gradual loss of pressure unless the piston or the cylinder just suddenly break. I’d caution against spending real money to rebuild an oil-less compressor, even a “heavy duty” model. I put a $50 rebuild kit in my 6HP Craftsman last year that included all the essential parts, but still doesn’t equal the original performance.
Like many other things, compressors have become easier to replace than to fix, hope your problem is the cutoff!
This isn’t an uncommon problem with some models of Chinese compressors & it generally isn’t the pressure switch, the problem being that for whatever reason the compressor pump can’t quite achieve the pressure switches cut off pressure.
I get the impression that motor power is inconsistent from one compressor to the next & that the motor specification is very close to the minimum required - it will go from empty (no load) to switch-off pressure (57>60psi ?) quite easily, but ask it to start under load & go from 40>60psi & things don’t go quite so well. You may notice that the sound while recharging is far more laboured than on the initial charge?
I’ve seen a few of these that will get up to about 50psi & can’t get any further - the motor will either stall or continue running slowly until the overheat switch cuts in…
I had the same problems with a small $25 Homier Distributing Co 1gal compressor I bought several years ago. It was a 0-115 PSI unit with regulator I picked up at one of their road shows. After about 6 months of use, it behaved just as you describe. I took it apart to see if I could fix it and found one problem was the little 'metal flapper valve" on top of the piston. It’s just a little piece of ‘beryllium copper?’ that opens as the piston descends (to allow air into the cylinder) and is closed by compression as the cylinder rises. A very simple thing but the threads for the screw that hold the ‘valve’ in place were not very precise and, after using it for 6 months, had worn from the constant movement - the valve just flopped around and couldn’t function. I re-tapped the hole for a slightly larger screw. Put it back together and same problem so took it apart again and after carefully looking at the fit of the wobble piston in the cylinder found the seal around the piston very badly worn . Decided it was beyond me to fix and, in frustration, it went out with the trash. I don’t mean to discourage but that was my experience with a very cheap ‘made in China’ compressor.
edit: I certainly didn’t mean that ALL inexpensive compressors ‘made in China’ are worthless. I have a Harbor Freight AB compressor that has worked fine for over three years (still working) and it’s made in China but it was also 3X the price of the HDC one. $25 for a compressor with regulator sounds to good to be true - it is, I think.
My garage compressor stopped comressing. It seemed to be stuck at 40psi, even after almost 20 minutes. The cylinder head turned out to be loose; I torqued the bolts down and the compressor started to build pressure again. You cold be having a similar problem.