How to diagnose an air compressor that won’t start. Fixing a Harbor Freight compressor

My 29 gallon Central Pneumatic air compressor from Harbor Freight would not start. I'll show you how to diagnose the problem and how to fix it.

[mariojunco]

Your absolutely right! Thank You! I fixed it!

[foxwood]

Glad you got it figured out .Most people dont have ability to diagnose problems and would junk it. I would have thought the starting capacitor first Check valve second then switch. Ive been lucky and saved a couple compressors from heap pile by just spending a bit of money and time to figure out the problem. Hope you get 500 hours more

[erichsh]

My HF 3 gallon McGraw compressor won't restart after initially compressing the tank. Eventually (1/2 hour or more) it will start again. i believe it is overheating but cannot find any way to confirm that, what to do about it, and how to reset it. The tank becomes almost fully charged (110 PSI)) and then the compressor stops.

[thegaragehub]

I just replaced that whole pressure control on my 9 year old 29 gallon harbor freight air compressor. It had cracked the 4 way body and began to leak. The only other failure I've had was the gasket from the head to the manifold going to the tank. It's nice they added the hour meter to the newer models.

[TF]

Darn it. That's a non-reversible motor.
Otherwise you can reverse polarity in the motor and use it as a handheld vacuum cleaner. 😃😁😉🙄

Actually somebody on YouTube shows how to reverse a non-reversible motor.

[TF]

By the way, you should never check a run capacitor the same way to check a 9 volt
The taste is absolutely shocking!!!⚰️

[kennydiel]

Laid my compressor down on the ground to look for circuit breaker, stood back up and it turned on. CRAZY

[apoach]

I bought the same 29 gallon compressor from HFT About 2 months ago and it doesn’t have an hour meter. Please share what you upgrade the pressure switch with.

[ronyerke]

There's no reset on your hour meter? Dang digital thing. Some analog ones used to have a reset button.
Grainger Industries sells a vibration activated hour meter by the way.

[JohnGotts]

Quite often I catch Harbor Freight selling rusty goods. Check your purchase in the parking lot, or if possible in the store.

[larrycroft]

Young man you have a very gifted mind. Your mechanical knowledge is wide and varied. But most importantly you have an amazing ability to communicate your subject matter so that it is easily understood. I have learned a tremendous amount watching your videos over the years. I have acted on your advice on particular pieces of equipment reviewed and disassembled by purchasing them. So far every one of them have worked well for me. I hope your time and intelligence is rewarded by this platform. Thank you for taking time to make these videos.

[kevinroebke]

Really like your reviews. What replacement pressure switch would you recommend as a replacement? Source?

[Broddi]

Could happen to any compressor yet the hf trolls bash it anyway. They hate hf but follow all their tools . Guess it helps them feel better about spending to much on their name brand china junk.

[TF]

I had a similar problem with a bench grinder because the centrifugal switch inside was bad and it would sit there and hum.
But I decided not to fix it because this way I could start the Grinder running in either direction by starting it by hand.

And a week ago I picked up a free air compressor on Craigslist and it would not start because I found out that it had a bad start capacitor. I knew enough about motors that was one of the first things I checked.
With no load at all on the motor when I turned it on it would pick up speed run normal and I would hear the centrifugal switch clicking inside so I knew it wasn't the switch.

[TF]

I had a similar problem like yours many years ago. The wiring on the switch only used half of the contacts and was burnt burnt.
So I cleaned the contacts and divided the amperage between two different sets of contacts.

Try reversing the polarity on the hour meter and see if it runs backwards.

[_Ptat_]

Those pressure switches are a pain in the ass to rebuild. Our HF compressor was leaking out of the pressure switch diaphragm so I had to take the whole contact switch mechanism apart, then used some RTV to fix the diaphragm. It’s not so much hard to put the pieces back together, it’s trying to get all the pieces back together under spring tension.

[johnysilver]

My compressor starts working and builds pressure up to 150psi but sometimes during work it will not start and won't keep tank charged. Sometimes it turns on only for a few seconds then goes quiet. Sometimes I hears something that it wants to start like air going somewhere through the pipe for about 2 second and then quiets and stays like that. Fails to keep up pressure in tank when I use it. Pressure goes low as 50psi but compressor doesn't start. Then I had to open drain valve to release remaining air pressure in the tank. Disconnect it from AC power for few minutes and it starts working again build up to 150psi again. I don't hear any air leaks. What could be wrong??

[ACoustaDC]

I love this channel. Hope you are getting a chance to work on the bug a bit.

[yojoebananas]

Seems shortsighted to build a compressor with a good pump, start caps and motor but put a cheap part that is high failure and essentielly “kills” the machine for most people.

[hubertrobinson]

You did good job finding the problem 2 months ago I was given a 10yr old just like that the switch was stuck on run I cleaned it worked for couple times then went back to sticking I bought on Amazon an identical replacement that working pretty good now