Outside central AC unit's fan won't run- unit seems ~dead now


  #1  
Old 07-13-04, 12:17 PM
kae
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Question Outside central AC unit's fan won't run- unit seems ~dead now

I have a very old outside central AC unit (got the house 3.5 years ago and the home
inspector said it was old then) that worked fine until yesterday afternoon. I was
getting chilly so I set the tstat a bit higher, and the AC turned off. Later it started
getting too humid so I set the temp a bit lower again. A few hours or so later I
noticed the house was still too warm. I checked the outside unit and the fan wasn't
turning, and I heard a buzzing noise coming from the unit. I turned the AC off from
the tstat and back on, and the fan started running perhaps 5 or so minutes later.
(There has always been at least a few-minute delay for it to kick on.) But then it
stopped running again very shortly thereafter (few mins), and the buzzing noise was
back. I checked the AC's circuit breaker on the house panel and it was not tripped. I
flicked it off and back on again just to reset things. Now the fan won't turn on at all,
and I haven't heard any buzzing/humming noise. BTW, when I set the tstat to auto
(and "cool") and turn the temp down, the furnace blower (to which the AC is
attached) comes on just fine. So it seems like the problem is with the outdoor unit.

After reading nearly all the posts on this forum and talking to a few friends, it
sounds like it could be the capacitor or a bad relay. I will go home tonight and check
to see if the fan spins freely with and without power, and check to see if there's
some kind of reset switch once I get the cover of the unit off. (I'll be sure to turn off
the circuit to the AC.) It was dark outside when all I started looking into this
yesterday evening, so I'll to check more things tonight.

Does anyone have any idea what the problem might be? I would think that the
buzzing noise + fan not running would narrow the list of problems down a bit.
Do you have a list of things I can check? (I have a cheapo multimeter that I'm not
too handy with, but I have lots of EE-type friends who are.)

I'll call a repairman if I need to . But since I was able to fix my refrigerator a year
ago (by reading troubleshooting guides online!) when 2 older repairmen failed to
find the problem (and Sears was going to make me wait 8 days just for a first visit
and hopefully a diagnosis while my food spoiled in late June in hot humid MD), I
figured I'd take a stab at fixing the AC myself.

Thanks, Kim
 
  #2  
Old 07-13-04, 03:30 PM
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is the buzzing the compressor running, or an electrical sound. if neither the fan nor the compressor is running, either the contactor or the dual cap is bad. if the compressor is running (little line will be VERY hot) and no fan, either the motor or cap is bad. hope this helps

be sure the breakers are on. fuses good
 
  #3  
Old 07-14-04, 06:47 AM
kae
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The buzzing noise is an electrical buzz, coming from inside the electrical panel
of the outdoor unit, from the little black box to which all the colored wires
are attached. The compressor is not making any noise, and neither is the fan
(and it's not spinning). The fan itself does spin freely with the power off and on.
The electrical buzz starts exactly when the 2-min "startup" delay ends, and stops
as soon as I turn off the cooling. (I don't suppose it helped my situation that when
I took off the panel to the electrical box inside the outdoor unit that at least a
dozen wasps flew out.! Seems they took up residence in there. I sprayed them
and used a stick to clean out the nests,. They're all dead now.)

I found a label on the unit- it says the brand is "Cumberland." Also one of the
"things" (don't know what bit of hardware it is) inside it has a date stamp of
May 1974. I know it's time to replace the central air system, but I'd be nice to
make it last the rest of this season.

Any advice on what I should do next? Are contactors or dual caps easy to replace?

Thanks!

Kim
 
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Old 07-14-04, 07:26 AM
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Wink

What is sounds like to me. All is ok there in the line of power and tstat. I think the points are gone on the contactor and you just need a now one of them mark down how it is wired and the color. Take it with you and get a new one. That buzz is it pulls in but the points are gone.We try to tell people to spray around the AC unit outdoors now and then. For bugs ,, ANTS will also do this to you.
Any advice on what I should do next? Are contactors or dual caps easy to replace?
YES

ED
 
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Old 07-16-04, 09:06 AM
kae
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Thanks for all the advice so far!

I was going to try and replace the relay to see if that fixes the thing,
but I haven't been able to find any parts stores that have even heard
of this model or model number.


The outside of the unit says "Cumberland" but the engraved metal plate
attached to the outside of the thing and schematic diagram inside the
cover panel both say "The Trane Company". The model number on the
metal plate is 0AUA-252B, the serial number is 4L-0822, and I believe it
was manufactured in 1974. I've done a rather exhaustive Google search
for info about Cumberland, Trane, this model, etc, and called several air
co parts stores (including one that carries specifically Trane) with *zero*
luck. Does anyone have any suggestions of who I should call to get a new
relay for this model? (I was hoping to get this current central air unit
running for a little while longer- until I can spec out a new one and hire
someone to install it.)

Thanks,
Kim
 
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Old 07-16-04, 11:04 AM
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If it is indeed the contactor just take it with you to the parts store and they can match it up with one that will work.

For the kicks of it are you sure you have 220V out there at the unit? There may be fuses in the disconnect hanging on the wall by the outdoor unit. Also look for any reset switches that may be hooked on one of the copper lines near the compressor.
 
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Old 07-16-04, 01:57 PM
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Like Matt said Take it with you it dont have to look the same just work the same and wire the same. I sold Trane then and dont know of any Cumberland at all. Trane was GE



ED
 
  #8  
Old 07-17-04, 09:48 AM
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contactor replacement

A contactor replacement for a 1974 condensing unit is really an optomistic view point... I think you have a head pressure controller that cuts in the fan and its not working because the compressor isnt either. If you have a meter, set it to the highest AC setting and place one probe on the power line feeding into the contactor. Observe where it bridges the gap, when it pulls in, place the other probe on the other side of the gap...if the contactor is good , it will read 5V or less, this test measures the contactors ability to pass the voltage over the gap to the other side where the load is... Do the same test to the other contacts.(usually two sets...not always though) Another way to check is to kill the power, remove the plastic cover on the compressor where the wires feed into it, and place one probe on the C and one on the S. The other test is to place the leads on C& R for line voltage... The C& S voltage may be a bit higher...thats OK...it should be. If you have no line voltage on C&R or C&S the contactor is bad...
 
  #9  
Old 07-19-04, 08:08 AM
kae
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Thanks for all the testing info- I'm sure it will come in handy for the future. But for
now, I need a whole new condensor unit. The first guy I had stop by for an estimate
wanted to make sure my unit was dead first (good sign!) and said the compressor
was shorted out and cooked. I knew the two wires connected to the compressor
looked black and fried, but I didn't realize there were supposed to be another
wire connecting the other two "prongs." !! (BTW there was no plastic cover over
where the wires are connected to the compressor.)

Now I could use a bit of advice to find the right contractor. I've had 2 come by my
house so far, one more is coming tomorrow, and I may get one more estimate.
All 4 have been recommend by friends.

First, I have a new (3 years old) oil furnace installed by the previous owners just
before I moved into the house, but I don't if they changed the evaporator coil.
Should I get a new evap coil no matter what? Also, all the duct work is in place,
and the coolant feeder lines are copper, in fine shape, and do not need to be
replaced.

The first guy would like to sell me a 12 SEER Carrier (or another brand if I so
desire) and said he'll check to see if they recommend a new evap coil. He said
Tranes are good, but they cost a lot more and you are mostly paying for the name.
(He also said one of his customers has had nothing but problems with her Trane,
and that each brand can have its problems.) Both the Carrier and Trane have a
10 year warranty on the compressor and 5 on the other parts. The second guy
basically only wants to sell me a Trane, or a Jantrol. He doesn't/won't sell Carriers,
and touts the fact that Trane makes their own compressors. So what? That could
be good or bad or irrelevant.

The first guy gave me a flat installation fee and said it would take him (alone
I'm pretty sure) about 2 hours to install the thing. If he has to do the evap coil
I'm guessing it might take a bit longer, but that replacement is pretty straighforward,
right? The second guy said it would take him and a helper 4 hours to install.
He definitely will change the evap coil to a high-eff one, and said he can get
12 SEER out of an 11.5 SEER Trane because of the high-eff coil. He would not
give me any ballpark figure for installation at the time (the exact numbers for
both guys should be given to me today). Also, 2 different friends said it took
one guy one hour when they had their outdoor condensor unit installed. Oh, and
the second guy never looked at the old unit to make sure it could not be repaired...

So my basic questions are, 1) should I get a new evap coil? 2) approx how long does
installation of the outdoor compressor take? 3) how long does installation of the
evap coil take? 4) are Carrier and Jantrol good-quality units or would you
recommend some other brand?

Thanks!!!
Kim
 
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Old 07-19-04, 08:53 AM
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Being that the unit is "very old" you should have them do a heat gain/loss calculation on the home to confirm you still need the same size. I doubt very much that they changed the indoor coil when they put in the new furnace so get a new coil to match the new outdoor unit.

Not knowing what part of the country you're in I can't say on seer you should get. If you're in a cold climate the 12 will be ok but if you're in a warm or hot climate you should go higher.

On your questions:
1.Yes
2.If it's straight foward 2-4 hours
3.Really depends but shouldn't be more than 1-2 hrs.
4.Carrier=good, Janitrol=Not so good, Trane=Good, American Standard=Good, Rheem=Good, There are many more good and low end units but the install is #1.
 
  #11  
Old 07-19-04, 02:06 PM
kae
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I'm in MD just east of Washington, DC, where it can get VERY humid in the summer.
Consumer Reports says 12-14 SEERs are best, because the higher the SEER the more
that can go wrong with the unit. And unless one stays in the house a long time the
extra cost for the higher-eff unit is not recovered. So the 12 SEER sounded ok to me
(esp since I may not be in the house that many years).

I have a ~1600 sq foot house with 2 stories (only 2 big bedrooms and one bathroom
upstairs) that's poorly insulated (built 1957 when energy was cheap). So now I'm
stuck between choosing a 2.5-ton unit or a 3-ton one. Any advice? Trane's web
site will offer model numbers but won't give a size. BTW, neither contractor has
even suggested doing the heat gain/loss analysis. I guess your advice then would
be to ask one of them for that analysis? There's another contractor coming tomorrow
at noon. I can ask this one if he doesn't bring it up.

Do you think a brand new, efficient, 2.5-ton unit would do as well or better than
a 30 year-old 3-ton air co? (The price diff quoted to me for a 3-ton Carrier
as opposed to a 2.5 ton was ~$100. So I'm thinking it's probably worth the extra
cost.)

Is there *anywhere* online I can look up the prices for air conditioners? I cannot
find even one web site that will tell me prices so I can compare one unit to another,
or one brand to another, and so I can find out what the contractor's markup is.

Thanks again,
Kim
 
  #12  
Old 07-20-04, 08:11 AM
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You can go to www.hvaccomputer.com and do a calculation on your own. Looking at prices online wont tell you anything because contractors get different pricing than public. Sometimes they end up paying more or less. If you were to find one and bought it online you would never find anyone to install it with a warranty.

If your house is pretty much the same as when the original a/c was installed and it worked fine just go back with the same size if you don't do the calculation.
 
  #13  
Old 07-22-04, 04:09 PM
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Wink The duct work???

Everyone forgets about the duct work.... If you need 3.5 tons and have a duct system that will only support 2 tons...your screwed! I think the cooling/heat load calculation is a good starting point... It gives you a good idea what you can work with... Then size the duct work to see what it will support along with the blower. Carrier is good, Trane is too, Also York, Stay away from Janitrol or Goodman, Rudd make a nice unit too, Keep away from Bristol compressors,...have the safetys put on if they don't come with it... ie HP,LP,freeze stat.
What do you think of a surgeon that say's, "I can do that breast augmentation in 1/3 the time, I'll through them right in"?
The gas recovery itself will be an hour, picking up the stock another hour at least...What is your concern in regards to how long it takes? Get the bottom line and get a list of what you'll get for it. I'd rather the guy that takes 2 days rather than 2 hours...you don't want this to come back and haunt you...
 
  #14  
Old 07-04-08, 06:09 PM
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Angry my ac unit outside stopped working

My ac unit outside stopped working, I tried to turn on the fan from inside the house, and it wont work either. I opened the unit outside and I pushed the button on the contactor and I will start it seems that it might be something related to the thermostat but I am not sure.
 
  #15  
Old 07-05-08, 11:09 AM
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condensing unit won't start...

First with a meter set to AC check to see if you have 24Volts to the contactor. If you do, replace the contactor. Next, check to see if anything could interupt the circuit to the contactor..ie does the thermostat 2 wire from the house to the condensing unit go straight to the contactor or does it go to something before that. A digital photo of the wire schematic should reveal that. Keep in mind, there may be a 5 min time delay from the thermostat if its digital. Does the inside fan come on using the auto and on positions?
 
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Old 07-05-08, 11:17 AM
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in MD just east of Washington, DC

Me, too.
If you want to check the cap I posted previously on two ways to do this.
 
  #17  
Old 07-05-08, 11:39 AM
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after re-reading all the reply's

I just have this gut feeling there is nothing wrong with the unit except a few burnt wires and maybe a bad contactor or cap. stop telling them to replace it. If they condem it, have them show you why it requires replacement. If the wire is burnt... replace it. If the compressor is bad, this is easily shown with a ohm meter. If you want to do this yourself let me know and we can do the test easily...
P.S. the minimum SEER you can get now is 13. I don't know where these 12s are comming from. Maybe some old stock from years past. That cut off date for 13 SEER was JAN 2007 I believe.
 
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Old 07-05-08, 02:30 PM
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The 12 SEER mentioned was because this thread was dredged up from about 4 years ago!

OP - 07-13-04 02:17 PM
 
 

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