DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Lennox AC Compressor Problems -- Capacitor?




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Old 07-19-2008, 11:54 AM  
SomewhatHandy
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Default Lennox AC Compressor Problems -- Capacitor?

Hi all;
I've been lurking in the shadows for a while and have come out with some good advice over the years. So, to start off... Thanks for all the past help!

I've got a Lennox 10acc-036-230-02 compressor (condenser?) that just started not working yesterday evening. After shutting of power, waiting a while, then restoring power, it continues to not work. Neither the fan nor the compressor are running, but both are humming and get very hot (and the capacitor seems to be warm, as well). If I give the fan a push, it'll run, but not as fast as it used to. The fan bearings don't seem to be an issue, as it turns freely. I have no way to evaluate the state of the compressor (that I know of).

From what I've picked up here (and other sites), my best guess is a bad starting capacitor. This unit uses a dual start 50 / 7.5 MFD 330 VAC, though Cozy Parts suggests that Lennox is now replacing them with a 50 / 7.5 MFD 440 VAC (which I've ordered). I should have no problem replacing the part once I get it -- it looks easily accessible. And yes, I understand the appropriate electrical safety concerns -- especially having been zapped a few times by capacitors I was sure could no longer hold a charge. :^o

Now, the questions:

1) Am I on track here, or are there other things to consider?

2) Is there a way to evaluate the compressor?

3) Most importantly, after several hours trying to track down a capacitor locally (northern VA), I could find nobody to sell me a part. If they had parts, they only sold to contractors, or they wanted to send a tech out for a service charge of 80 to $300, plus $80 for a capacitor (which I bought for $20 from Cozy). Is it always this hard to find parts locally, or am I not calling the right folks? Where have y'all obtained parts in the past?

Thanks, again!



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Old 07-19-2008, 02:18 PM  
glennjanie
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Welcome SomeWhatHandy:
Yes, you have a good start on the trouble shooting. You may test a capicitor with an ohmmeter (preferably with an audible tone). Just disconnect the wires and touch the ohmmeter to the two leads; your audible ohmmeter will go to a high pitched whine and quickly taper off. Remember there is a capicitor on the compressor and another on the fan; its good to test both of them.
To evaluate the compressor; unplug the three wires to it and use the ohmmeter again (this time you need a digital readout which you will record in all three positions) put one lead against the compressor body making good contact, touch the other lead to each of the three contacts and record the reading. Your readings should be such that any two added together will equal the other. If that doesn't happen the compressor is dead.
While you are digging out all these wires to disconnect you will probably run into one on the compressor that is burned off and not making contact at all. Cut the burned portion of the wire off, crimp a new female plug to the end of it and plug it to the compressor. Clean all three contacts with a wire brush or 100girt sandpaper.
You might also check at the contactor for burned off wires.
The wholesalers will not sell to walk-ins because they are protecting their full time mechanics who want to keep a closed organization. Find a United Refrigeration wholesaler and sound like you know what you are doing, it may or may not work.
Let us know how you turn out with this. We may be able to help more as you experience more or take pictures of your work.
Glenn



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Old 07-20-2008, 06:23 PM  
kok328
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The particular capacitor that you have, has 3 poles on it. It must be reinstall exactly how you removed it. One pole is the common one of the other two goes for the fan and the other one goes to the compressor. You don't have separate capacitors for the fan and compressor.
See if you have a Grainger's near you, they should have one in stock and will sell to walk in's.
Before you go resplicing connections and stuff, you'll have to start at the beginning w/some basic troubleshooting.
Is the compressor contactor engaged?
Are you getting proper voltage to the compressor?
Are you getting proper voltage to the fan motor?
If yes then the component is bad.
Is the thermostat calling for cool?
Are there any fuses, main feeds or on a circuit board, that are bad?
Is the high pressure switch tripped?
Is the low pressure switch tripped?
Is this a 3phase system or a single phase system?

Answer these questions and we should be able to provide an accurate diagnosis.

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Old 07-21-2008, 04:30 PM  
SomewhatHandy
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Default Updates on Lennox Compressor

All;

Many thanks for the good tips. Here's the latest.

I've looked over all connections, none were questionable, but I cleaned connectors, re-seated the clips, and tightened screws. There are no circuit boards, just one relay (which appears to be clean and working -- it at least provided power to the motors).

I'm hesitant to check voltages (I can deal with 120, but get a bit nervous around 220), so I haven't done that yet. However, as both the compressor and fan motors were quite warm (too hot to touch), I'm starting off by assuming they both had power going to them. Oh, and it's single phase.

I performed Glenn's suggested check on the dual-use capacitor. I don't have an audible ohmmeter, but even on the 2000 M ohm setting, I barely registered any measurable resistance (effectively infinite, though it did flicker some numbers occasionally). I don't know if it's significant, but I can hear a fluid sloshing inside the can -- I'm guessing it's the oil.

The resistance readings on the compressor were OK, too.

So, as of now, I'm sticking with the capacitor as the primary culprit. Hopefully, it'll arrive from Cozy tomorrow. I'll update when I get it in.

Again, many thanks for the hints and tips. Hopefully, I'll get some pix of some of the more successful projects posted in the gallery (especially my deck and finished basement/bar).

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Old 07-21-2008, 06:05 PM  
kok328
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Leave the unit off until your new capacitor arrives.
If the new capacitor doesn't do the trick, then you'll have to check voltage to the unit.
It sounds like you've lost a leg of power.

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Old 07-23-2008, 02:53 PM  
SomewhatHandy
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Default Got Cool?

All;

Got the new capacitor from Cozy. Installed in a few minutes, and I now have a functioning AC.

Further examination of the old capacitor seems to indicate that at least one of the lugs are not connected electrically.

Thanks to all for the tips and suggestions. I'm glad I was able to get it done myself and save several hundred dollars.

Cheers!

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Old 07-23-2008, 06:14 PM  
kok328
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Cool ! (sorry about he pun ... lol)

I forgot to mention that aside from the bad terminal, a capacitor is likely to swell, when it goes bad.

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Old 08-09-2011, 02:33 AM  
clow
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Hi i have a similar cenerio with a linnox 2 ton ,furnice functionig ok but nothing from the condencor. The contacter is close for call ,the cap is new and working ,red and green on board are flashing in synnc,,still condcor not running. Help

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Old 01-19-2013, 03:40 AM  
randyortan
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wow! this is a great post. I am sure a lot if MSI users will be interested in this.



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