How To Spot A Bad Oiler, Or Electrolytic

[Grainger49]

Three days ago my upstairs air conditioning int stopped working.  (This makes the listening room uninhabitable)  The compressor and fan were not running but the recirculating fan was running.  It was 86 upstairs.  I checked the breaker, the voltage at the compressor and the condensate overflow switch.  Everything was normal.  Into our bedroom window went the air conditioner we have for emergencies.  I called the service folks today.  There is a huge backlog and the service manager suggested checking for 24V AC on the contactor, checking for a manual reset on the over pressure switch (I don't have one) and checking the capacitor.  I had figured the cap was ok because neither the compressor nor the fan were running.

This is what I saw when I opened the service panel.  The rounded top indicates complete failure.  For reference, the top is horizontal when new.  Often a bad electrolytic will bulge but I have never seen one this badly domed.  I have seen both the top and bottom of electrolytic capacitors swollen, but never the side.

[groomster]

G49,

     I have had two similar instances the same exact thing, only on my whole house AC.  (Glad it is still under warranty, because those caps are pretty hefty in price!)

-groomster

[Grainger49]

I paid ~$40 for the one cap.  I will buy an extra for each unit and not let it stop me again.  Then I have to learn to put in the R22 gas... and more.

[Laudanum]

Thats a dual section cap from the looks of it.  Starts/Runs both the fan and the compressor.  Luckily, I have a full 10 year warranty on the ac.  They have replaced the cap/caps 3 times now.  However, only one section went bad the first time, the section for the fan.  I believe the cap was a 40uf / 7uf but no bulge on the top of that one when the 7uf section went south.  They left the original cap in for the compressor and then installed a USED one for the fan.  Not knowing much but knowing enough, I told the tech that he would be back soon because the original cap was going to fail and the compressor would no longer run.  When you get a 10 year full warranty, they cheap out as much as possible.  Sure enough, no more than two months later they were back replacing that cap for the compressor which had a bulging top at that point just like the one in your picture. They replaced with single section, thankfully a new one.  The following summer (last summer) they were back again replacing that used fan cap they put in the year before but from memory, the cap showed no physical sign of problems.  That AC unit has gone out every summer (Florida) for something minor for the past 4 years.  Fan motor, fan blade, those 2 caps, and the cap again.  ALWAYS on friday night or on the weekend.  I bought a 12000 BTU room ac window unit when the fan motor went because it required a part order.  It's installed in the living room window with a quick and easy way to close off the room with plastic tarp just for the now annual occassion.  Everyone just crashes in the cool living room for a night or two or 7.  2 years left on the warranty then I'll either replace the unit or buy a spare cap.  I should be tarping the living room again anytime between now and August.  :-) 

[Grainger49]

Laudanum,

Mine was a 5/35uf.  I will guess that the 35uF side failed pretty catastrophically and it opened the lead to the fan (5uF) as well.  The dome on the top of the cap still amazes me.  I'm not sure the picture does it justice.  It looks like an old distribution transformer from the 50s.

I'm also pretty amazed at the efficiency and low current of today's window units.  I remember the big, two men to handle them, old units.  They needed about 10-15 amps to run them.  They tripped weak breakers all the time.  They dimmed all the lights in the house when they cycled on and they cost an arm and a leg to run.  

[Laudanum]

Yep, I remember as a kid having the thru-wall units before we got central ac.  The unit i bought for the living room was a cheapie and it isnt very efficient relative to what's available.  But it isnt a beast like those old units you mention and that I remember.  I Wasnt going to spend a lot for an emergency unit.  It's a cheaper LG but works when we need it.  I saw the cap when the compressor finished it off.  Just like you describe and your picture shows. Pretty cool actually.  No pun intended.

[Grainger49]

Just for yucks I am considering finding a cheap source for these caps and changing them every 2-3 years regardless of condition.  The service call charge will offset the PM costs here.  Same thing for the fan cap in the air handler for the upstairs.  The downstairs unit includes the compressor and all air handling functions in one big box.  I had never seen these before I moved to Knoxville but they are everywhere here.

[Paul Joppa]

Grainger? Grainger the capacitor junkie? You feeling OK? I thought you'd be the first to seek out an upgrade capacitor!

Can't help but think there must be better quality, more reliable capacitors than those which come with low-priced consumer appliances ...  :^)  I think it's CDE who have some interesting lifetime plots on their web site, as a function of temperature and voltage. I'll bet the stock stuff is right on the edge of adequate voltage rating, for instance!

Maybe a spike protector would be a good idea. I'll admit, a regenerator would be a little over the top for an AC unit though.

[Grainger49]

Yes, yes, that is me!

LOL, but I don't think there would be an audible difference with upgrade caps.

I'll take a look at CDE and see if there is a longer life replacement that is affordable.  When I worked for Alcoa in a rolling mill I wrote a PM that replaced Honeywell motors on Reliance DC drive systems, the MOR to be specific, every year.  The cost of the motor and replacement covered only a part of an hour's downtime charge.  

We may have supplied aircraft sheet to your former employer.  The plant I worked in was built for WWII starting in Jan. 1942.  The controls included Mag Amps and Amplidynes (did I spell that right?).

[2wo]

I've used these guys.

http://stores.ebay.com/JEA-CAPACITORS/Motor-Start-Motor-Run-/_i.html?_fsub=8&_sid=70580994&_trksid=p4634.c0.m322

Before the upgrade my AC was cold and sterile. Now. Well, warm was perhaps not the word I was looking for, Ill get back to you. But I can tell you good break in is the key ...John     

[Grainger49]

John,

Thanks, I will open the units and get a list of what I need.  Too late this morning to get into the AHU in the attic I would fry now, tomorrow.

Yesterday was the first day in 17 days that it didn't hit 90 or above.