Author Topic: Home AC help  (Read 5319 times)

fiveoh

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Home AC help
« on: May 24, 2015, 07:06:24 AM »
Our A/C went out yesterday and I was hoping maybe someone here would be able to tell me how to fix it.  I have no prior experience with A/C stuff but I know those repair guys charge a lot! 

It will turn on and blow a little air but its not cold.  The outside unit(not sure of the name for this) fan spins but very slowly compared to what it normally does. 

Any thoughts?  Questions?  Answers?  :) 

Thanks in advance.

Vwjedi76

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Re: Home AC help
« Reply #1 on: May 24, 2015, 11:00:57 AM »
YMMV, but our outside unit wouldn't turn on at all. I went on youtube and watched videos on how to change the fuses. That fixed it for us, luckily. It was $7 per fuse, and required 2. Your motor may need replaced, but you can start with the fuses and a good cleaning on of the outside unit (just spray out debris with a hose from the inside out). If that doesn't work you can always take your fuses back and get a refund if you saved your receipt. Hope that helps, A/C repairs usually start at $100 and skyrocket from there. Good luck!

forummm

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Re: Home AC help
« Reply #2 on: May 24, 2015, 11:46:04 AM »
You have a central AC? You should probably just call an HVAC professional. We aren't going to be able to diagnose this without seeing it in person. Any number of things could be wrong. The compressor is the part outside.

zolotiyeruki

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Re: Home AC help
« Reply #3 on: May 24, 2015, 01:17:22 PM »
This time of year, there are lots of possibilities.  My money is on "low on refrigerant and evaporator coil is iced up".

fiveoh

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Re: Home AC help
« Reply #4 on: May 24, 2015, 03:20:44 PM »
So after some googling I pulled the panel and checked out the capacitor.  Am I correct to assume this is probably bad and not supposed to be bulging at the top like this?

Anyone know a good place online to order a new one, or which one of those numbers is the part # I need?

zolotiyeruki

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Re: Home AC help
« Reply #5 on: May 24, 2015, 05:58:07 PM »
No, the capacitor should not look like that.  Amazon has a replacement for $30:
http://www.amazon.com/CAPACITOR-ONETRIP-REPLACEMENT-COLEMAN-S1-02425895700/dp/B0085HHPYE

This is *definitely* a DIY-able fix.

forummm

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Re: Home AC help
« Reply #6 on: May 24, 2015, 06:22:52 PM »
I have had AC capacitors go out over the winter a couple times.

shadowmoss

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Re: Home AC help
« Reply #7 on: May 25, 2015, 03:49:37 AM »
Things that should go without saying, but I'm gonna say anyway:

Before working on the unit, turn off any and all electricity.  Really.

Also, that size capacitor can still pack a wallop if you get between the contacts.  Once the electricity is off, take something (insulated from your person) and short between the contacts.  What capacitors do is store charge and release it suddenly.  Hopefully not into your hand(s). 

Read all the precautions and follow them.

zolotiyeruki

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Re: Home AC help
« Reply #8 on: May 25, 2015, 06:39:58 AM »
Things that should go without saying, but I'm gonna say anyway:

Before working on the unit, turn off any and all electricity.  Really.

Also, that size capacitor can still pack a wallop if you get between the contacts.  Once the electricity is off, take something (insulated from your person) and short between the contacts.  What capacitors do is store charge and release it suddenly.  Hopefully not into your hand(s). 

Read all the precautions and follow them.
Good points.  My tool of choice for discharging capacitors is a screwdriver with a plastic handle.

forummm

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Re: Home AC help
« Reply #9 on: May 25, 2015, 07:08:15 AM »
Things that should go without saying, but I'm gonna say anyway:

Before working on the unit, turn off any and all electricity.  Really.

Also, that size capacitor can still pack a wallop if you get between the contacts.  Once the electricity is off, take something (insulated from your person) and short between the contacts.  What capacitors do is store charge and release it suddenly.  Hopefully not into your hand(s). 

Read all the precautions and follow them.

+1. Also, that capacitor appears to have something wrong with it. It may not behave how you think it would normally.

dcheesi

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Re: Home AC help
« Reply #10 on: May 25, 2015, 07:39:13 AM »
Yeah, my outside unit had the same behavior and it turned out to be the capacitor.

fiveoh

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Re: Home AC help
« Reply #11 on: May 25, 2015, 09:47:46 AM »
Thanks guys!  Ordered from Amazon.  I used a screwdriver and checked it with a volt meter before I messed with it.

dycker1978

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Re: Home AC help
« Reply #12 on: May 25, 2015, 11:31:09 AM »
Thanks guys!  Ordered from Amazon.  I used a screwdriver and checked it with a volt meter before I messed with it.
A volt meter will not pick up and stored charge in the capacitor.  Use a insulated screwdriver and discharge it by touching the post together with it.  It will snap, but better there the on you hand.

fiveoh

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Re: Home AC help
« Reply #13 on: May 28, 2015, 07:03:40 PM »
Fixed!  Thanks for the suggestions/help.

zolotiyeruki

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Re: Home AC help
« Reply #14 on: May 28, 2015, 10:26:01 PM »
Fixed!  Thanks for the suggestions/help.
Nice.  How long did it take?

fiveoh

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Re: Home AC help
« Reply #15 on: May 29, 2015, 10:14:16 AM »
Fixed!  Thanks for the suggestions/help.
Nice.  How long did it take?

Took 3 days for the part to arrive but the actual labor probably 10 minutes.  A friend of mine said he paid $250 to have his replaced last year.  $220 savings for 10 minutes of work and a few days without A/C. 

dycker1978

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Re: Home AC help
« Reply #16 on: May 29, 2015, 10:22:23 AM »
Fixed!  Thanks for the suggestions/help.
Nice.  How long did it take?

Took 3 days for the part to arrive but the actual labor probably 10 minutes.  A friend of mine said he paid $250 to have his replaced last year.  $220 savings for 10 minutes of work and a few days without A/C.

$1320 an hours... good savings I would say.

a1smith

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Re: Home AC help
« Reply #17 on: June 14, 2015, 10:26:44 AM »
A few comments to help people that will need to change their dual run capacitor in the future.  Many of the comments are on how to do this job SAFELY so you can enjoy retiring early!
  • Disconnect the AC supply before working on the AC unit!!! By electrical code, there should be a disconnect box close to the AC unit.  You pull out an interruptor that usually has two fuses (one for each phase).  Usually, you can rotate the interruptor 180 degrees and reinsert it to store it but not reconnect the circuit.  If you are not 100% sure about this just keep it somewhere else until you are ready to restore AC power to the AC unit.
  • Once you disconnect the AC use a meter to ensure there is no power coming into the AC unit.  There are three wires coming into the unit.  Check voltage between the ground wire (screwed to the unit frame or side of electrical enclosure) and the other two wires and make sure they are both 0V.  Make sure you are measuring AC with your meter.  If you have the meter set to DC and you measure a hot AC line you will read 0V!!!!!
  • The proper and safest way to use a meter in this case is to measure a known hot voltage (120V outlet in house) to verify meter functionality.  Then, measure the AC unit.  Then, go back and measure known hot voltage.  This makes sure you have meter set properly (AC, not DC) and that the meter didn't get fried when measuring the voltage on the AC unit.
  • Since this capacitor has three terminals it is two capacitors in one can.  The larger capacitor is for the compressor, the smaller capacitor is for the condenser fan. For capacitors with two wires it is only one capacitor.
  • For this unit, the 45 uF capacitor is for the compressor, the 5 uF capacitor is for the condenser fan. There are many other sizes; the capacitor for my unit is 35/5.  Make sure you buy a capacitor with the proper rating(s).
  • The other important spec is the rated capacitor voltage; it is usually going to be 440V or 370V. Some capacitors are marked 440V/370V which means you can use the capacitor for either voltage. If you have a 440V rated capacitor you MUST use either a 440V or 440V/370V rated capacitor. If you have a 370V capacitor you can use a 440V/370V capacitor which can help it last longer. Usually, a capacitor marked 440V is the same as 440V/370V.
  • Take a picture or write down how the wires are connected.  The terminals are almost always labeled C, FAN, HERM.  C is common (ground), FAN goes to the condenser fan, HERM goes to the AC compressor.
  • The capacitor introduces a phase shift in the electricity going to some of the motor windings which allows the motor to start.  Once the motor starts the phase shift is created by the rotation of the motor. So, if your condenser fan is not rotating or rotating slowly it is usually a bad run capacitor.  If it is not rotating try spinning it with a screwdriver blade once the power is off to make sure the motor isn't siezed.  NOTE: if you try spinning the condenser fan when power is applied it will probably start spinning because then you are doing the capacitor's job.  Beware of flying screwdrivers!!  That's why you do this test with the power off.
  • The bulging top of the capacitor means that it overpressurized.  These capacitors have a pressure interruptor in them that disconnects the terminals from the (bad) capacitor.  This prevents damage to the compressor and/or fan due to a failed capacitor.
  • The formula for a capacitor is Q=CV.  Q is the charge, C is the capacitance, V is the voltage.  So, you can check for a residual charge on a capacitor with a voltmeter set to DC.  If you measure using AC you will read 0V!!! Measure with the AC supply disconnected.  Measure between C and FAN for the fan capacitor, measure between C and HERM for the compressor. If either of these readings is non-zero you need to discharge the capacitor.  Short the appropriate terminals with a screwdriver as mentioned above and make sure you are not in the circuit.  Wear safey glasses.  Even if the capacitor has no charge you may still want to short it with a screwdriver to be double sure.
  • With an overpressurized capacitor the terminals have been disconnected.  Usually, the capacitors bleed down to no charge over time.  However, make sure not to crush the top of the capacitor because that could make the terminals contact the capacitors again which could be charged.  If it is charged the capacitor could discharge through the terminals now.
  • If your meter can measure capacitance you can measure between C-FAN and C-HERM to see what the fan/compressor capacitor capacitance values are.  Usually, a bad capacitor is going to read 0 micro Farads.
  • If the capacitor is wet on the outside it means that it is leaking electrolyte.  None of the capacitors use PCB's any more so that is not an issue (unless you have a really OLD unit).  The capacitors are now marked "No PCBs" so you can check for that labeling. While some of the capacitors now use vegetable oil there are others which are using a proprietary electrolyte such as the Dielektrol VI used in OP's capacitor.  So, it is best to handle with gloves and make sure you don't touch your eyes/nose/mouth/etc until you wash your hands/arms well.
  • When installing the new capacitor make sure you have adequate clearance at the terminal end from any metal components such an enclosure wall. The same clearance as the original capacitor should be fine especially if it is the OEM installed capacitor.

NOTE: This is not an exhaustive list of safe electrical work practices.  If you are familiar with electrical work then this is a relatively easy job.  If you are not familiar with electrical work or are uncertain about any aspects of this work you should contact a qualified HVAC professional to do this work.

Coincidentally, I just had to replace my AC run capacitor last week.  I got the part for $11.70 on Amazon.  Home Depot had the same part for $8.70 but the shipping time was longer.  The 45/5 capacitor for OP is $10.72.  If the weather isn't so hot maybe you want to wait a few extra days to save the money.  It is free shipping if you pick it up at the store.

I bought a Packard dual run capacitor; I checked on several HVAC forums and contractors were happy with that brand.  Besides the voltage and capacitance you might also want to check the diameter of the can so that the existing bracket will work.
« Last Edit: June 14, 2015, 10:39:04 AM by a1smith »