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.

[@foxwood67]

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

[@JohnJones-oy3md]

Exactly. I recently curb-shopped a small HF compressor that looks brand new but won't power up. Needs a new power switch. KZbin has been a great help to me in simple fixes like this.

[@larrycroft470]

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.

[@Jjjjjjc]

This is honestly one of the most positive messages I've ever seen 👍

[@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.

[@PastPreserver]

Glad you figured it out ill keep that in mind if mine starts giving me issues. good work 👍

[@TF856]

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.

[@hubertrobinson8825]

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

[@JoseSanchez-wb5rz]

Very good Young Grasshopper.

[@bleach_drink_me]

For what its worth, my old harbor freight compressor like yours is still going fine years later. So is the Mcgraw and my personal favorite, a Kobalt quiet tech. It's going strong as well. I think it's 4 years on the CP and 2.5-3 years on the Kobalt and Mcgraw. I have 3 oil filled compressors and 1 oil less. On the oiled I change it once a year unless it starts looking bad. However on all 4 I make sure to drain them every time I am done using them.

[@TF856]

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.

[@johnathanprice8255]

Excellent!!! Thank you so much bro 90% sure I need some reed valves for mine

[@kevinroebke8050]

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

[@Jason_henke]

I actually today just bought my stores last one that was on clearance and the quality was surprisingly good and this is the same one but they must of changed some things there is no more hour meter and the control/pressure switch was tuned to the left for better access but couldn't beat 380 bucks

[@Kamal_AL-Hinai]

Hey man, please upload more 🧡

[@tomcordes1768]

An informative video. Thanks.

[@ToolTeardowns]

Thanks for watching.

[@ACoustaDC]

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

[@ToolTeardowns]

Thanks for the kind words. Not working on the Beetle much. I've been busy with other things.

[@broddans]

Thank you very much! Was my check valve

[@JohnGotts]

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

[@22apoach]

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.

[@_P0tat07_]

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.

[@chrissharon3213]

How would tighten the belt on these? It’s a challenge to separate the compressor from the motor.

[@erichsh58]

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.

[@kewrock]

I have a HF beltless oil lubed compressor. It's very difficult to get started in the winter. I have to switch it on and off repeatedly while pushing the circuit breaker button. I think the oil thickens up in the cold.

[@ToolTeardowns]

You might want to look at the tank check valve and unloader valve. Sounds like maybe there's pressure remaining in the head.

[@kewrock]

@ToolTeardowns it only happens in winter. I think I need a lighter oil.

[@michaelnance5236]

Question, I have a HF compressor (direct drive) that you have to bleed off some of the air pressure at times to get it to start. It tries to start but, until enough pressure is released it just kicks the breaker after a few seconds. Once, it's running it pumps up fine, just takes a little extra effort from time to time to get it running. I have had this for years and kept the oil changed, garage kept, and emptied between uses.

[@ToolTeardowns]

Sounds like a problem with the unloader valve or tank check valve. Both of those would allow pressure to stay in the pump, which makes it hard for the compressor to start.

[@beeepizzle]

Bad start capacitor?

[@ronyerke9250]

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.

[@johnysilver1853]

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??

[@theinfernalcraftsman]

Grr. I never get those easy fixes. It seems everything I work on the part that fails is always the hard to diagnose one and the one that is the... Oh that never fails... For my stuff I always start with the obscure failures first. My 60 gallon decided that one of the rod bolts was too tight and loosened itself to the point that the rodcap fell off... I had an oiless one that the bolt holding the piston top broke... Looking forward to some more content it's been a while. How is the car coming?

[@ToolTeardowns]

I haven't worked on the Beetle much. I've been busy with a new job and kids. I bought a couple motorcycles, so I've been tinkering with those and debating whether to try some motorcycle content on the channel. Thanks for sticking with the channel during this slow period.

[@theinfernalcraftsman]

@@ToolTeardowns When you get to it you get to it. The daughter has been out of the house for several years and better half is wanting grand kids so at some point it'll be busy for us again as well.

[@andreiusdixon4687]

I have the same problem mine is humming when I switch it on ....

[@DAILYDIME69]

Bee careful with that hour meter mine shorted out today and was blowing sparks out the side of it I unplugged hour meter and compressor still works fine

[@onpoint6674]

Mine only fills air ones, when the air starts getting low it doesn't restart, I have to empty the air my self so it stars again.

[@ZEUS-xt3dt]

my compressor was stuck so i put some oil in the chamber using the airbreather

[@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.

[@joshuaward692]

Now, put some dielectric grease on those contacts so it doesn't happen again.

[@kelton5020]

"and now it works" flips switch and the compressor explodes.

[@TF856]

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 KZbin shows how to reverse a non-reversible motor.

[@Broddi169]

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.

[@jcadult101]

You must have missed he already returned the first one. This, being the second, failed at 25hrs But please, continue to praise the brand. The parking lot sales before the pandemic would always have these in the return area. Some larger stores I've seen as many as 10 of these red tagged. Sunday, everything red tagged drops 1/2 off the red tag. If I recall, these would be $75-80, well worth the price of the tank and plumbing bits. With luck, you got a compressor to do a job. With great luck it outlasts the 1 job.

[@jcadult101]

@Russell Phelan LOL. I have seen plenty of these for under $100. I have an 80gal, 3 piston that was new, still bolted to pallet that was $150. $800 welders for $350. Last day of the parking lot sales all the red tags were 50% off and they had piles of these 29gal CP units.

[@TF856]

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

[@KingKatura]

Now go get a Harber Frieght Chicago Electric Impact Wrench & make it stop working so you can tell me why its not getting power..