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Hi There,
I bought a replacement air pump for my Harbor Freight 21 Gallon Compressor.
Now i’m trying to get it wired up correctly and i can’t seem to get the new air pump to start.
Steven, thanks for the photo. It helps. It certainly looks like you’ve got the wiring right. The lower cord is the power supply, and the upper cord is the cord to the motor it seems. You’ve also got the ground or “earth” wire connected.
Do you have a voltage tester? If not, it will be hard to check as you’d want to know – with the tank empty – if power is actually flowing across the switch, as well as ensuring that power is flowing to an across the On/Off switch. Can you check and let us know? Thanks.
I have a mid 2000s 30 gallon Craftsman compressor that I bought for $50. I live in Germany and the gentleman I bought it from brought it from the US. The motor is 110v only.
He told me that he plugged it in with a transformer when he got here and it ran for a few seconds then tripped the house breaker. He reset the breaker and then the capacitor made a loud pop and smoke came out.
I bought it thinking it was only a bad capacitor. I replaced both capacitors with brand new capacitors and plugged them in. I ran it on a 1600W transformer and it kept blowing the breaker. So I bought a 3000W transformer which should have been plenty of power for the 110v at 15 amps. I ran it and it blew the garage breaker. I reset and it ran for about 15 seconds, then the same issue. Loud pop, white smoke, and capacitor is fried.
I’m wondering what the issue may be. I was really hoping the new capacitors would work and I could run it okay on 220v here in Germany.
Can anyone help me diagnose my issues? I’m wondering if there is an internal issue with the motor or if it’s just an issue with it being 110v running through a transformer.
Any help is appreciated. I am not an electrician but I have tools and can diagnose if given appropriate instructions.
Hello Chris. Can you access the motor information plate? Is it rated for 50/60hZ? Just wondering.
I’m wondering too why a simple plug adapter couldn’t have been used versus adding a transformer? I was of the impression that the adapter plug that allows a 110/120 Volt item to be plugged into a 220 V power supply, had a transformer built in to reduce the voltage? Guess I’m wrong.
When you remove the belt from the pump to the motor, can you rotate the pump sheave fairly easily? Any noise from the pump. I ask as if the motor is being overloaded by the force necessary to drive the pump, that could cause cap problems. Thanks.
Thank you for the reply. The motor is 110v 60hz only. Not 50hz/60hz. Of course you know we run 50hz here in Germany. I assume this could be my issue. I will say though that I have a craftsman 20 gallon compressor also that is dual voltage but also 60hz only that runs fine plugged directly into the wall (wired for 220v) with no issues at all.
There is no belt connecting the motor and the pump but I can rotate the fan which moves the piston up and down very freely. There are no sounds I can hear.
When the motor was running it definitely did not sound right. It sounded like it was sluggish. Also I want to add that it was the start capacitor that blew both times. The run capacitor appears fine. The capacitor was completely shredded. The plastic casing was all that was left. All internals blew out the top.
Would 50hz on a 60hz motor cause these issues? I’m wondering why my other compressor runs fine. Both use a Weg motor.
Hey Chris. I’m no electrician, so I can’t offer authoritative electrical advice. I can say that on the motor it should say if it’s 50/60 hz. If not, I wonder too if that’s the issue? I wish I could tell you for sure.
Anyone else help Chris with this issue?
I had a thought about this issue. Is it possible that the capacitors were installed in one anothers place by the previous owner, or that there is an issue inside the motor that keeps it from switching from the start capacitor to the run capacitor?
Well Chris, I found this:
“Run capacitors are used for continuous voltage and current control to a motor’s windings and are therefore continuous duty. They are generally of a much lower capacitance value. … A start capacitor can never be used as a run capacitor, because it cannot not handle current continuously.”
Source: Motor Capacitor FAQ – Capacitors – Product Guidestemcoindustrial.com › Product Guides › Capacitors
So if the caps were switched, yup, that could be the problem.
Also, if you pull the motor cap off the shaft end of the motor, if there was a centrifugal switch there, make sure it’s not seized up.
Sorry to keep posting, but I keep digging a little deeper, and I have some more information.
I removed the motor endplate, and looked at the wire routing and got a better idea of how the starter switch and centrifugal clutch work. The capacitors were hooked up properly, so that isn’t the issue. I tested the start switch with a multimeter, and it appears to be working. There is continuity when the bars on each side are touching down, and no continuity when they are up. I am now thinking that the issue is with the centrifugal clutch itself.
I moved the clutch open and closed, and while it moves, it sounds a bit squeaky and does not have the characteristic snap when moving to the neutral position (closed?) that I’ve seen demonstrated on some YouTube videos. I would like to try replacing the clutch, but I’m not sure how to get it off the shaft (there is a bearing at the end that I’m not sure how to remove) and I don’t know what to source for a replacement. I took some photos, but I’m not sure how, or if I can post them on here.
Is there a way, besides powering the motor with the end plate off and watching the clutch to see if it opens to diagnose if it is in fact sticking closed? I have two run capacitors that should both work (I ordered a new start capacitor to replace the one that blew up) but I’m apprehensive to use a run capacitor in place of the start capacitor even for troubleshooting.
Chris, please, no apology necessary. It’s good to see someone tracking down all the reasons for, and trying to resolve, issues with their air compressor.
I’m going to have to rely on our network of visitors to try and provide the answer for the last question, or, perhaps if you have a motor rebuild shop anywhere where you live, you might contact them and ask. If you get a response, it would be a kindness to others grappling with the same issue if you would post your findings as a comment.
As to photos, I’m puzzled that you cannot upload some. There should be a paperclip icon to the right in the main comment, and follow up comment areas where you post a comment. Clicking on that icon will allow someone to upload up to five photos at a time.