Question/Problem with capacitor

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Old 08-12-13, 11:01 AM
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Question/Problem with capacitor

Hi guys, I am having a problem with my outside air conditioning unit. I left for the day, and when I returned and turned the a/c on, it blew hot air for about 20 minutes before I realized something might be wrong. So I went outside and noticed the fan blades on the outside unit weren't turning at all. I don't hear any loud humming noises on the outside unit fan or compressor, just a very slight humming noise I cannot pinpoint which is barely noticeable. Turning the fan blades with a long screwdriver doesn't get it to start up. The system is a Nordyne/Maytag P3RA-048K and from what I have read it has a dual mode capacitor because it has 3 wires.

So I did some reading, and learned about the contactor and the capacitor. I can see the contactor pull in when I turn it on, although one time out of about 7 test tries I did see a slight small spark in it, nothing big. The contactor appears to be working from what I can tell it is pulling itself in and I see it pop back out when I turn it back off. It looks new and clean.

I discharged the capacitor with a screwdriver, and removed it. I tested it with a multimeter, and it seemed to test good although it is slightly rusty. I have a cheap digital multimeter, and it went from 0 to about 2000 then back to 1. If I reverse the jumpers, it starts at about -400 then slowly goes back on through to 0 and all the way up to 2000 before reading 1 again. Same with other side of the capacitor. I have read it should go back to 0 but I am guessing because I have a cheap multimeter or because it is digital it is reading 1 instead.

I also removed the fan wires thinking the fan motor was bad. I touched the wires to contactor's inputs and the fan started humming loud, and if I push start it and then quickly touch the fan wires to the contactors supply it turns on, either full or medium speed depending which wires I touched to contactors inputs.

I put it all back together, and try to turn it on, I see the fan blades barely twitch but no movement to speak of at all, no loud humming noise from the fan motor like when I hooked it up to the contactor inputs as previously mentioned. There is nothing written on the capacitor besides 621697 and 0031. Nothing in the label inside of outside unit cover, specifications, owners manual or wiring diagrams about the capacitor.

Does it sound like it could be the capacitor? I have read even with a bad capacitor that you can usually push the fan blades with a long screwdriver and get it to start. Is it possible the capacitor could fail to where it will not let any power through to the fan and compressor?


Thank you!
 
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Old 08-12-13, 11:15 AM
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I'm thinking that it may be the contactor. The reason is because you said that the condenser fan will run when you manually connect the fan wires directly to the contactor input (AC voltage). The capacitor is used to start the motor, so it's normal for it not to start by itself (without the capacitor) when connecting the fan wires directly to 240VAC.

Here's what I would do to check the contactor. Since you said you have a multimeter, set it to AC volts. With the thermostat set to cool and set to a low temperature (so it's turned "on"), check for voltage across the output terminals of the contactor. You should see ~240VAC across both the input and output terminals when the contactor is enabled.
 
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Old 08-12-13, 11:52 AM
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Thanks for the quick response, it is 90 degrees in my house right now! I checked the contactor inputs and it read from 247-256 range. I checked the contactor outputs and it read -4 to 3. I think you must be right! I should have checked that first! Thanks so much Bob! Do you think I could have caused any damage to the capacitor or compressor in the process?
 
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Old 08-12-13, 12:23 PM
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It's unlikely that you did any damage doing what you did. Hopefully, when you replace the contactor, everything should start working again.
 
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Old 08-12-13, 12:43 PM
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Thanks again, I wheeled my air compressor over to the unit and blew compressed air into and around the contactor, and as I did that I could smell burnt bugs and burnt plastic immediately. It seems like the contactor is broken, the flat metal peice on the part the moves in and out - that connects the inputs and outputs is defiantly way too loose. I was able to turn the system on again, and push that same flat metal piece all the way into the contactor, and the fan immediatly turned on, as well as the compressor! So my house is already 2 degrees cooler and blowing cold air out of the vents again! Everything seems to work although I am guessing it only works if I manually push that piece in with a screwdriver because of it missing plastic around it or being too loose. The A/C stores only sell to companies here, so I will have to order a new contactor online for $20. I looked up the part number for it and they even have a picture of the same one! So thanks Bob for saving the day!
 
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Old 08-12-13, 12:59 PM
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There should be stores that sell to the public..... they don't only sell just to the trade.
 
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Old 08-12-13, 06:16 PM
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Most supply houses are WHOLESALE ONLY.... but you may find one (or one that will work) locally at a Grainger store
 
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Old 08-12-13, 08:33 PM
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Thumbs up

Thanks for those suggestions, I had to call about 3 places before I somehow found a contactor relay about a 30 minute away at Appliance Parts of Ocala, they seemed to have just about everything in a small store. I was determined to find it and I was willing to call everywhere to see if I could buy it locally before I ordered it online. The important thing was I didn't have to be a contractor to buy from them, I made sure to ask them before I went. I had to hurry because I only had 45 minutes until they closed to get everything back together and drive there. It was a little more than the online one I found, at $26.99 but worth the drive and money not to have to wait days and days enduring the heat crossing my fingers that it would be in the mailbox!

Everything was the almost the same on the new contactor but I had to cut two connectors off that had spade terminal connectors on them and strip those 2 wires to go under set screws on the new contactor because it had set screws on the outputs instead of screws for spade terminal connectors. The place I went was busy, I had to wait in line! The new one is made in China but I guess almost everything is nowadays. It also has a cover for the piece that moves so that bugs, dirt and water won't get into it.

My A/c has been working great ever since, I still need to vacuum a large amount of leaves out of under the fan blades but that can wait, other than that everything looks clean, I went ahead and cleaned some more with my air compressor while it was out there. I might paint the grill above the fan blades and the top of the fan motor someday too because they are heavily rusted. It is working better than ever now. Randomly, a couple times every few months it would take a few minutes to turn on and I am guessing this was the same problem that I fixed today.

Everyone in my house is happy and this is the quickest I have ever had my air conditioning fixed, in less than 24 hours! It is now 78 degrees inside when last night it was 88 degrees inside with all the windows open and ceiling fans on! So thanks everyone especially Bob and everyone at DoItYourself.com! This is my new favorite website and I will try to help out in other ways if I can.
 
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Old 08-12-13, 09:36 PM
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Glad you found a store you could buy from. Here the supply houses are mixed. They won't sell all parts to non trade people but they'll sell most everything else to anybody.

Good job there
 
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