Compressor repair success story -- Hitachi EC12

[roger wiegand]

I have a portable Hitachi EC12 compressor that has served me well for many years. A couple of years ago it got so that it wouldn't run on an extension cord, and this winter it stopped running pretty much altogether, especially after it was at pressure. It just hummed. Many of you will recognize this as the sign of failing motor capacitors.

OK, I thought I'll try replacing them, but then I discovered that it needed two caps at a cost of $50-60 each, plus $10 postage for the "correct" replacement parts. So, the dilemma-- invest ~$120 in buying capacitors for a 25 year old compressor when that might not fix it-- when a whole new compressor costs $300?

The answer-- McMaster Carr. Two new caps with the correct specs for $7 each, a little epoxy to replicate the attachment bolt on the OEM parts (could have used a couple radiator clamps and an angle bracket), and we're off to the races! It now runs like new, even on an extension cord.

A lot of folks online complain of this problem with this compressor, swearing that they will never buy another Hitachi. If you happen to be in that camp, spend the $20 for a pair of generic capacitors and swap them out, you might be happy you did!

[Mark Bolton]

Always rewarding to same something from the scrap heap. Nice work. Probably run forever.

[Bill Dufour]

Please ad the MFD to your post for future reference.
Bill D.

[roger wiegand]

Please ad the MFD to your post for future reference.
Bill D.

Sorry, what is a MFD?

[Mark Bolton]

The size of the capacitor in microfarad

[Mike Cutler]

Capacitors are generally fairly inexpensive as long as you're not trying to source them from the manufacturer. There are a myriad of capacitor cross reference charts on the internet.
In addition to the µFD, micro farad, rating, you need to know the working voltage rating. If the capacitor is not marked, there are also website, with charts, that can provide the µFD range application for a motor, based on size and voltage.

[Mark Bolton]

Im guessing the reason Bill suggested posting the capacitor ratings is because the motor/equipment manufacturers determine specific capacitor sizing based on the motor and equipment they are running and the application charts commonly available are just a coarse estimate based on the motor size knowing nothing about what the motor is doing or connected to. A 1hp motor doing one job may have a completely different capacitor from the equipment manufacturer when its doing some other job.

We have gone through this on a few motors and the wild *** guess from the charts has always worked fine but having a definitive result pop up for the specific make/model/application would most definitely simplify things. Even landing on an application that is close with the same specs would be helpful.

[roger wiegand]

Doh! The old capacitors were marked 40 micofarad and 425-500 V; I consulted an electrical engineer friend and he told me that the 40 uF 250V ones offered by McMaster would be fine for the purpose (it's a 120 V motor). So far so good.

[Bill Dufour]

Glad to see the voltage is double the supply volts as it should be. The cap sees full voltage which is about two times the RMS as reported for ac power lines.
Bill D.

[Jeff Duncan]

For anyone with the stalling problem.... before spending money on new parts check to be sure it's not the compressor head vent tube, (sorry not sure of the correct term at the moment). This is a frequent cause of problems with these Hitachi compressors and the fix requires nothing more than removing a little rubber stopper and cleaning/sanding it down a bit. Obviously it wasn't the same problem for Roger, but I had that problem and fixed it in 5 minutes with a little sandpaper.

good luck,
JeffD