A/C Motor Start Capacitors - Where To Buy?

Assuming lightening struck twice and the reason your A/C stopped working this time is the same as it was the last time. (But don't bet on it...)

Look for an industrial electrical supply house, or an HVAC supply place.

Jeff

Grainger, McMaster Carr, any good motor supply or repair house.

I get mine, at my local HVAC parts wholesale house. All you have to do is get your EPA card, establish a business, get a sales tax number, and go into the trade. No problem.

I curious on what he's going to do when the start cap doesn't fix the problem. Here in St. Louis there is a no return policy on electrical parts. lol

Well, you know how it is with AHR posters. He's already replaced the thermostat three times, so it's got to be the capacitor?

That's funny, most AC condensing units don't have start capacitors. It is usually an option though. You may be referring to the oil filled "run" cap that is connected to the start winding. A start capacitor is going to be of the electrolytic type along with a mechanical or solid state start relay.

TDD

No S*it?? When did they start doing that?

Many years ago. Start capacitors are going to be a high value electrolytic type in a black Bakelite case along with a potential relay. You will see it on commercial refrigeration equipment because the compressor often has to start under a load. Under ideal conditions, a home AC or refrigerator comp is going to have time for the pressures to equalize after shutdown before the thermostat calls for cold. Last summer I had to remove the factory hard start PTC thermistor from our office condensing unit after it shorted. That particular setup did not use a separate start capacitor. I replaced it with a "Kick Start" device consisting of a potential relay and a large electrolytic capacitor. A start capacitor and relay costs the manufacturer a few dollars more per unit and you may not think it's much money until you realize that manufacturer has to purchase a million of them. Here's a page that shows what I'm referring to:

Which was very common on older compressor units.

OK, just to tie up the loose ends on this one:

1. It turned out the capacitor was fine. I thought it migh be the cap because the last time that's what it was and the guy that replaced it told me that it's often the problem. The replacement was one he had already and I don't know how old it was when we installed it. I figured if I could get one and install it myself it would be a cheap enough experiment that it was worth it if I could avoid having to pay a pro.

1. I assumed it was a "motor run capacitor" when I went looking for a replacement and saw references to them. Maybe it wasn't. It's a capacitor with two sides, one labeled "fan" and the other "therm" with a common in the center.

2. In the end I ended up calling in my neighbor again. This guy has been doing heating, A/C, electric and plumbing in the neighborhood for about 50 years. Nice guy and very helpful and I hate bugging him. He determined it was low on freon, and charged it. He also checked for leaks and cleaned out the grill(?) with a hose. I paid him a little more than what he asked (still a bargain) and gave him a framed photo of his house with the sunset behind it.

1. I don't know how old the unit is. It was there when we moved in in '98. I'm going to guess it's about 15 years old.

-Scott

No Comment

Just so you know, the terminal marked "herm" means hermetic which refers to the hermetically sealed welded can compressor. I bet the wire was yellow for the "herm" and brown for the "fan". The common terminal could have been just about any color except green.

TDD

IIRC it was yellow for common, reddish brown for fan and blue for herm. I'm pretty certain about the yellow.

-Scott

You may be right, I've been putting in so many hours lately that everything is running together. My hair hurts, my toenails itch and my eyeballs are squeaking. Last service call was over at 8:00pm.

TDD

What a shame to hear that the guy has been doing this for 50yrs and cant find a simple refrigerant leak. Refrigerant doesnt wear out or go bad. It leaks out. You have a leak. It will continue to leak and it will continue to cost you money. Not to mention that it is hard on the equipment running it low on refrigerant. It is also hard on the environment by depleting our ozone although that's a whole nother crock of crap. Bubba

How small a leak is one supposed to find? One that leaks out not quite all the refrigerant in 15 years?

Just a few years ago, I was told (IIRC) that A/C techs are finding and repairing leaks of 4 ounces of refrigerant per year, and that ones around or less than 2 ounces per year are often too small to find and are often tolerated.

- Don Klipstein ( snipped-for-privacy@misty.com)

I've been using a stop leak made by Cliplight Manufacturing Company for several years and have had very good luck with it. The stuff is great for those tiny inaccessible leaks in evaporators.