air compressor help

David Anderson · August 26, 2009, 09:13:40 AM

My Harbor Freight air compressor had a capacitor meltdown. It was running fine, attempted a restart and couldn't turn the motor. I pulled it out of the bus and one of the capacitors has a melted spot on it. (see picture). Would it be worth trying to replace the capacitor or should I replace the whole compressor. It has been very reliable.

The capacitor is listed as 70uF +/-5% MK SH
250Vac DB HPFPU, 50/60HZ 25/7021 There is another set of numbers lower on the case:
CH0012083-96 E2026163

Len Silva · August 26, 2009, 09:37:50 AM

Absolutely, change out the capacitor, not a big deal and not all that expensive.

Make sure that the unloader is working properly. If the compressor tried to start against a loaded head, that might have caused the capacitor failure. More likely it just failed on it's own.

Sojourner · August 26, 2009, 09:44:42 AM

Change capacitor would my choice for around 10 dollars. Whatever, never replace it with lower voltage rating. The higher uf (mean larger physical size) the better starting power but might snap the drive shaft.

Quote from: Len Silva on August 26, 2009, 09:37:50 AM
Absolutely, change out the capacitor, not a big deal and not all that expensive.

Make sure that the unloader is working properly. If the compressor tried to start against a loaded head, that might have caused the capacitor failure. More likely it just failed on it's own.

Amen!

The bottomline is keep it cool air via outside air and exhaust the heated air will increase compressor's life.

And keep draining the pump's air tank to avoid too many unnecessary restarts.

Example

Sojourn for Christ, Gerald

David Anderson · August 26, 2009, 10:39:01 AM

Why does the compressor have 2 capacitors??

David

Len Silva · August 26, 2009, 11:10:17 AM

You have a start capacitor and a run capacitor. This will explain it better and simpler that I can.
http://www.allaboutcircuits.com/vol_2/chpt_13/9.html

JohnEd · August 26, 2009, 02:26:45 PM

Do what Gerald and Len said. Always keep elect stuff as cool as you can....within reason. Caps are less sensitive to temp than the motor would be. If this compressor is in a closed space you should consider a ventilation fan of some sort. Regardless.....run it for a while and then feel the side of the motor. Real warm is OK. Hot is not.

John

David Anderson · August 27, 2009, 05:27:47 PM

Phooey,

I found a new start capacitor, installed it and the compressor ran like a top, for about 3 minutes. All of the sudden the capacitor began to enlarge, then kaboom. It exploded and sprayed this gooey stuff all over my shirt. I unplugged an inspected it. The goo was oozing out. Oh, well, I fired it up again and it started right up, but after about 50 seconds the capacitor started smoking and was super hot to the touch. I did this about 5 times and it always started and ran fine, but lots of smoke.

I assume the start windings in the motor are seized or something. Anyway, I now have a new compressor and I'll use this one for an extra tank. Sometimes it just doesn't work out the way you want it.

David

JohnEd · August 27, 2009, 05:45:59 PM

David,

If your start circuit was bad it would not "start". It is the run winding that is shorted. Time for a new Harbor Freight motor. Yours may still be under warranty. The replacement motor would be a cheap item.

I handed them a torque wrench that went breasts up today. Didn't even have to fill out a form. Just got the replacement off of the shelf and walked out....with their permission.

Now who said the walking around with an assault rifle slung was not a good thing.

Just kidding about the rifle.

John

David Anderson · August 27, 2009, 09:31:40 PM

The compressor was 8 years old. I got my money's worth. Time for a new one.

David