Dead compressor and fan...

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  #1  
Old 07-17-10, 11:01 PM
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Dead compressor and fan...

Have a 10 year old Goodman central A/C that was not cooling well. Tech found 3 issues:
1. said to stop using the permanent/clean-and-reuse filters and to use throw-aways instead.

2. he replaced the contactor.

3. he topped off the feon saying we might have a slow leak.

Ran fine for a week. Left for a week's vacation with thermostat set to 84. When we returned, we turned the thermostat down to 76 but the house did not cool off.

Our house has always been slow to cool down during high temp days (dehumidifies well, but slow to cool); so it was many hours before it occurred to me to that I had a problem.

I could hear the inside blower, but the air was not very cold. Outside, the fan was not turning at all. I reset the breakers making sure to wait about 10-15 minutes before moving the thermostat to the Cool position. I hear a click at the outside unit, but still no fan. I checked at the outside unit for 220 and 24 volts - not the problem, power was reaching the unit. Tried turning the fan with a stick... fan turns freely but does not spin up with power. Tested fan with stick with power off and it turned freely.

Called a different tech. He listened to my description of the problem and announced that it was a bad capacitor (he didn't even have to get out his volt-meter... he knew it was a bad capacitor). Well, he replaced the capacitor and that did not change my symptoms at all.

He said he didn't know what was wrong. Had power, new contactor, new capacitor... perhaps it was the cycle control box put on the system by PSE&G (this unit allows the power company to override my A/C's call for cooling... to help them balance loads). Said, if it was not a problem with the PSE&G box, then I needed a new compressor. Also said that they no longer made compressors with SEER ratings as low as mine (10 SEER), but that putting in a 13 SEER would probably work ok.... and we should replace the fan while they were at it. There is no humming sound as in either the compressor or fan trying to work (there does seem to be some minor humming coming from the contactor).

His boss called me the next day to say he and the tech talked about my situation and they feel I should be getting a whole new system (replace the inside and outside units so that they were matched and more efficient than my old system).

My questions:
1. Can I assume that I do need to replace the outside unit (compressor and fan) as a minimum?

2. Assuming I do need to replace the outside unit and am considering replacing the inside unit as well... The A/C system uses the furnace blower (a 1987 Lennox Pulse system). Is my choice of central A/C limited by this furnace (in terms of the amount of room in the furnace for A/C coils and blower efficiency)?

Thanks a bunch for your insight.
 
  #2  
Old 07-18-10, 10:31 AM
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You need to ask an AC tech to check fan motor and compressor to make sure if they are bad, also freon level again while he is there. Fan motor is cheap. they can fix that easy. but if the compressor is gone, you will need to think about if you just want to replace the compressor(or may be condensing unit), or replace the whole system. Get an estimates on both before making a decision.
 
  #3  
Old 07-18-10, 10:40 AM
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so neither the compressor or the fan outside turn on? what happens when you push in the contactor? It would be unusual for the fan motor and the compressor to go out at the same time. and even then something should make a sound. And its true they stopped making 10 seer compressors but that doesnt mean they are in short supply, in my area atleast. Something seems strange, it seems like your not getting power, even though that doesnt seem to be the case. can you confirm 240v to the both sides(top and bottom) of the contactor when its pulled in?
 
  #4  
Old 07-18-10, 02:09 PM
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I am seeing 119V on each leg to the contactor. When I push in the contactor, I see 119V from each leg (voltage to the contactor is coming in at the bottom and voltage out from the contactor is measured at the top). And, of course, there is only voltage coming out at the top leads when the contactor is depressed. Leads are Red and Black, contactor is a double pole. I am measuring 119V by placing my black tip on the green ground and my red tip on first the Red leg and then on the Black leg.

When I set the thermostat to Cool, I can measure 23.5V on those leads from the thermostat. Setting the thermostat to Cool also causes the contactor to depress, making the Click sound. No other sounds are noticeable, not from the fan or the compressor. The contactor stays depressed, with no sounds (although I can detect some minor vibration in the contactor) until I turn the thermostat from Cool to Off. I measured where the leads came in from the house first, and then on either side of the contactor. (The red lead from the thermostat is the one that goes into the Cycle Control box that PSE&G has mounted. My assumption is that, by measuring the voltage where the lead comes out of that box and connects to the contactor, I have confirmed that the 23.5V coming from the thermostat is actually making its way to the contactor (i.e., the PSE&G box is not in a Cycle Off state).

Regarding the "ask an AC tech to check fan motor and compressor": I asked if there was any way for him to do so and he said something along the lines of removing the rusting bolts holding the fan in place, disassembling the fan, and checking the windings was not recommended because of the potential of damage and time required on one hand, with the symptoms of "not a vibration, squeak, or hum" to indicate they were even getting power (so why bother). He did not check the freon level (my observation of his thinking seemed, again, to be why bother). Would low/no freon cause these symptoms?

I tried to push for measure, measure, measure to determine what is broken, but he could not get his head past... there's power, the contactor works, the capacitor is new, but there is no apparent effort on any part of the fan or compressor to function... no noise at all. He opened the top grate holding the fan, spun the blades, talked about issues with removing various fan parts; he removed the insulation cover from the compressor, noticed that some of the cover inside was chewed up, perhaps by a mouse, knocked on the compressor, commented again on the lack of sound; and then put it all back to together again.

This unit also has a small starter assist capacitor thingy connected to the big capacitor. I don't know how to 'test' this device with yellow and red leads. I did not see the tech test it with a meter either.

My 'suspicion' is that, while we were away on vacation, something went wrong, but because the system was still calling for cooling, it eventually burned out both the compressor and the fan. But then, I am ignorant and untrained.
 

Last edited by TinkerTrouble; 07-18-10 at 03:00 PM.
  #5  
Old 07-18-10, 07:33 PM
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A bit strange. Hard to guess what might have caused both the fan motor and the compressor to shoot craps together.
The only thing in common, at least that I can think of, is the contactor.

Here is a way to check. Turn off power. Disconnect capacitors. Measure ohms on the load side of the contactor. You should measure low resistance. If not, both motor windings must be open. You can disconnect the fan, and measure the fan motor and the compressor windings separately.

While you were gone, were there major lighting strikes? It's conceivable that could have caused both motors to be fried.
 
  #6  
Old 07-18-10, 07:43 PM
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Not sure what kind of AC tech you got. his attitude is questionable. If one does not hook up both gauge and multimeter do the checking, get another guy. Both fan and compressor can be checked with a multimeter. Fan is cheap, I can understand if the AC tech is a lazy person, but the compressor is expensive, you need to check at least 1. Ground(short), 2.Open winding, 3.Locked rotor, before you condemn it and spend that $1500+ dollars to replace it. In fact the fan can be easily checked same way. If you opened the unit already. it only take 15 minutes to check both. The fan and compressor are kind of independent to each other. As mentioned by ender2272, it is unusual that both of them go out at the same time. So, you need to check both of them out. The start capacitor is for your compressor, you need to make sure that capacitor is still good- use a good multimeter to check its capacitance. Also, make sure freon is at good level, most compressor won't start if it is too low.
 
  #7  
Old 07-20-10, 08:48 AM
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OK... I turned off the power, disconnected the capacitors and put my multimeter to the wires for the compressor and the fan motor. My meter is a small digital multimeter from Radio Shack, so it does not measure capacitance. For the following tests, I set the meter for Ohms in AUTO mode. AUTO selected the 400 range for all of these results. Would you please help me interpret these results?

Compressor:
Black - Yellow - 1.9 ohms
Black - Red - .9 ohms
Red - Yellow - 2.7 ohms

Fan Motor:
Black - Brown - 55.1 ohms
Black - Purple - 50.8 ohms
Brown - Purple - 105.7 oms

I admit to being unsure of what I am doing, so feel free to ask for clarifications.

I tried to test the capacitor, but the numbers started out being all over the place. I set a tripod to record my efforts, but now the meter does not move past the OL that it starts with, i.e, I get no reading now. I think I need to see if a local shop will test it/them (the small one too) for me.

Thanks for your insight.
 
  #8  
Old 07-20-10, 03:04 PM
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You know how sometimes you overlook the obvious? It occurred to me while eating lunch that I forgot to 'meter' the obvious... only because its a test I understand!

I tested from various compressor and fan leads to ground using the continuity tester setting:

Compressor:
All 3 leads (Black, Red, Yellow) showed continuity to ground. My interpretation is that means the compressor is shorted out. I did not have time to look at where the leads attach to the compressor... there might be a dead steel mouse draped across the 3 connection points (dreaming of a cheap fix).

Fan:
Continuity testing showed no short for the Brown or Purple leads. In my rush, it missed the Black lead, will check it later.

So, unless one of you have a different perspective, I believe I have a shorted out compressor. Yes?

The local plumbing supply house would not talk to me or sell to me (not a licensed tech) so I took my capacitor to an electric pump outfit. They confirmed the 40/5 capacitor as good. The small power booster starter thingy was a different story... he had no idea what it was, but it did not seem to be a capacitor from the wild readings on his capacitor tester.
 
  #9  
Old 07-20-10, 04:40 PM
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I 'm so embarrassed. Evidently I was not careful enough when doing my continuity testing. I went back to check out the 'missing' black fan lead and learned the following:

1. None of the compressor wires were shorted to ground (which means I can stop wondering why the circuit breaker never flipped off).

2. All the compressor wires are shorted to each other as tested by the continuity tester. Perhaps one of you might have known that from looking at the readings shown earlier, but not me.

Evidently the 'missing' fan black was laying against the housing and connected in such a manner that I was really measuring against the compressor black when I thought I was measuring against Ground.

Same conclusion though... bad compressor.
 
  #10  
Old 07-20-10, 05:14 PM
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Originally Posted by TinkerTrouble View Post
2. All the compressor wires are shorted to each other as tested by the continuity tester.
Not so fast. The individual motor windings are just a few ohms. You can't use a continuity tester - only an ohmmeter.

Look at the motor winding diagram to make sense out of what your are measuring.

Do you have a brother in law that knows this stuff?
 
  #11  
Old 07-21-10, 10:35 AM
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Not so fast. The individual motor windings are just a few ohms. You can't use a continuity tester - only an ohmmeter.

Look at the motor winding diagram to make sense out of what your are measuring.

Do you have a brother in law that knows this stuff?
Sorry, no brother-in-law that knows this stuff. Could not find a motor winding diagram online, either. I did measure with an ohmmeter before using the continuity tester and recorded the following:
For the following tests, I set the meter for Ohms in AUTO mode. AUTO selected the 400 range for all of these results. Would you please help me interpret these results?

Compressor:
Black - Yellow - 1.9 ohms
Black - Red - .9 ohms
Red - Yellow - 2.7 ohms

Fan Motor:
Black - Brown - 55.1 ohms
Black - Purple - 50.8 ohms
Brown - Purple - 105.7 oms
The compressor results are consistent with your statement that the ohms will be small. Do the large ohm readings for the Fan motor seem problematic to you? Should I tell the next tech to remember to bring a motor winding diagram in order to verify the readings because this problem seems so strange (I don't recall seeing a tech whip out any paperwork while troubleshooting in the past)? Thanks again for your insight.
 
  #12  
Old 07-21-10, 11:36 AM
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Looked at your test numbers. the compressor seems OK, no shorts(per your ground tests), no open winding between terminals since you got ohms, no hums (often locked motor do that). UNless there are some kind of mechanical failure, I can't think of any other reasons. Your fan test looks a little strange, the ohms are on the high side. those numbers are not normal. At this point, If I were you. I'll do the following. Get a new fan motor, and a good starter kit for your compressor. make sure you have power to the fan(120v)and compressor(240v) terminals, and test them again. (on your compressor terminals, is the yellow your START, red your RUN , and black your COMMON ? can't tell with just colors)
 
  #13  
Old 07-21-10, 12:42 PM
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Originally Posted by clocert View Post
Get a new fan motor, and a good starter kit for your compressor. make sure you have power to the fan(120v)and compressor(240v) terminals,
Normally, the fan motor and compressor both run at the same voltage (240V).
 
  #14  
Old 07-21-10, 01:49 PM
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You are correct. should be 240 for the fan, Thanks.
 
  #15  
Old 07-21-10, 04:21 PM
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i see you measured each side of the contactors voltage to ground and got 120 on each leg, but what you should have done was go across both sides at the same time and see if you get 240. i bet you wont
 
  #16  
Old 07-21-10, 06:33 PM
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Originally Posted by ender2272 View Post
i see you measured each side of the contactors voltage to ground and got 120 on each leg, but what you should have done was go across both sides at the same time and see if you get 240. i bet you wont
I bet he does...............
 
  #17  
Old 07-22-10, 10:19 AM
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Well, busy morning at the ol' AC...

I took off the fan/grill assembly and cleaned everything up. Took new measurements at the wire posts for the compressor by removing the wires and testing from the connection posts to a clean spot on the housing and then again on the large tube (same readings from both 'ground' points to each wire post).

Meter set on ohm / AUTO. Meter selected range of 40 M ohm and measured 30 M ohms on each post. Measurements between posts were the same as shown above (in the .9 - 2.7 ohm range).

I was not willing to dismantle the fan motor housing to get to where the wires connect so I tested from the wire ends to a clean spot on the motor housing... the meter showed no reading at all (resistance reading). I repeated the wire-to-wire readings and they were the same as before (much higher resistance readings than for the compressor).

First Question: Do 30M ohm readings on the compressor seen ok or do they indicate a short?

After reassembling the unit, I traced the main wire feed from the circuit panel out to the disconnect box mounted on the side of the house, next to the AC unit. The wire is a direct run. I colored the white wire with a Red marker inside the circuit panel. Using my meter, in Voltmeter setting, I verified 119V each leg (Red and Black) and 240V across them at the panel.

I went out to the disconnect box and measured the same numbers (and I colored the white wire with a Red marker).

I went to the contactor and measured 119V on each leg and 0 (zero) Volts across them!

I turned off the circuit breaker and went back to the disconnect box... a continuity test across the 2 fuses showed that one was bad (no continuity). How both legs showed 119V at the contactor is beyond me...

I purchased a new 20 amp, HRCI-R, Type D, Time Delay fuse.

2nd Question: These fuses have a 'channel' around one end. Does this mean that they need to be put in with respect to a certain polarity (e.g., the channel end goes to the load side/ or to the panel side)? They were installed differently in that the channel end for one wire leg faced the load/AC equipment, but on the other leg, it faced the panel.

clocert: The leads for the compressor: Red and Black provide the 240V and the Yellow goes to the capacitor (I don't know how to respond to labels like Start, Run, and Common in this case.)

Question 3: Given the above, would you recommend I insert the new fuse (polarity?) and give her a try or replace the fan motor and compressor start thingy first?

BTW: You guys are GREAT! Beer 4U2 I just had another company out and the bottom line is "they don't have R22 parts so I need a whole new system" ($4550 for a seer 13 American Standard). The last tech still hasn't gotten back to me with an estimate/recommendation (not that he ever figured out what the real problem is).
 
  #18  
Old 07-22-10, 11:15 AM
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From your new test numbers I believe you have a grounded compressor, your meter should not deflect at all. Once you have a reading, it is a bad compressor (and that is why you have a blown fuses result). Your fan is a different story. go to youtube, search for 'how to check fan motor', a video from 21footxpress will help you a lot.
 
  #19  
Old 07-22-10, 03:18 PM
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So I called an AC Service whose number I got from the Goodman web site to request the cost of a new compressor installation. They said they can't just order the part and come out to replace it. I have to have them come out for a service call first ($178) and then the tech will confirm the parts needed. Well, I said, let's say as a money conscious consumer I would like to get 3 estimates for the replacement of the compressor, can you tell me what that would cost. Answer: No. Only after the service call.

Well, assuming other companies are the same (and not telling me that I need a whole new system like the guy that came this morning), that means I need to pay at least $150 for each estimate to replace the compressor. Ouch!

End of rant!

I figure, if it's broke, then let's play with it a little more. So I put a fuse in (facing the way the old one was... channel end towards the load), disconnected the compressor, and turned on the system. After the 5+ minute delay the fan spun up very nicely. Great, I feel confident that the fan is good enough. The power mystery, while not understood by me (since when does 119V + 119V = 0V and if the fuse is shot on one leg, why don't I see 119V + 0V = 0V?), is solved.

Then I re-connected the compressor and called for cooling again. It's cooling now which kind of surprises me. I would think that a short in the compressor would blow the fuse fairly quickly even though it is a time-delay fuse. It's been running and cooling for about 1/2 an hour now. The large tube has some condensation on it and feels fairly cold, and the small tube feels nicely warmed (been like this for the past 20 minutes).

Is it possible that the compressor is ok, or am I damaging some other part of the system by letting this unit cool down our home for the first time in 11 days?
 
  #20  
Old 07-22-10, 03:44 PM
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Glad to hear that your system is running again, but with that small electricity leakage (high ohms to ground), I am not sure how long it can run, but hey, one day is one day, one week is one week. post back and let us know....
 
  #21  
Old 07-22-10, 05:06 PM
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Why 120+120 /= 240v

The reason you got 120v to ground from each leg but not 240 across them is because your contactor probably has a solid conductor from one line terminal to the load terminal, while the other is interrupted and operated by the 24v coil in the contactor.

That means that even when the thermostat is off (contactor not pulled in), there is voltage potential on -both- sides of the system because it comes in line2, out load2, and through all the components to load1. So from load2 to ground and load1 to ground, you're measuring the same source voltage. Then you go from one to the other and it's like putting both leads on the same side of a battery, or an inch apart on a live wire- no difference in voltage=no voltage reading.

Make sense?
 
  #22  
Old 07-22-10, 08:10 PM
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I guess it's all relative... 30 milli-ohms (the M means milli?) seems small, but when it should not be there... well, 30 M ohms could be pretty big.

Jones1: The contactor is a double-pole so I would not expect to see the potential there. I don't see how voltage potential can get from L1 to L2 or L2 to L1; at least not until 24V pulls the contacts in to open the possibilities of all the stuff on the Terminal/load side. There is no neutral in play to possibly pick up voltage potential through a neutral or ground bar...
 
  #23  
Old 07-22-10, 08:53 PM
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I think M is one million. the bigger the better. I believe the leakage is very small. you may be OK for a while. put a bigger fuse in there (I did not tell you to do that) will last you even longer.
 

Last edited by clocert; 07-22-10 at 09:14 PM.
  #24  
Old 07-22-10, 09:18 PM
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Originally Posted by TinkerTrouble View Post
Jones1: The contactor is a double-pole so I would not expect to see the potential there. I don't see how voltage potential can get from L1 to L2 or L2 to L1; at least not until 24V pulls the contacts in to open the possibilities of all the stuff on the Terminal/load side. There is no neutral in play to possibly pick up voltage potential through a neutral or ground bar...
You know, I thought that you had said it was double pole, but when you described what you found and I couldn't find where you'd said it, I thought I was mistaken. I can't imagine then how you got 120 on both sides of the contactor's incoming end...unless it was closed at the time of course. Otherwise...geez. I'll have to ask the guys at work in the morning or it'll keep bugging me.
 
 

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