Compressor strangeness

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  #1  
Old 02-22-18, 03:05 PM
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Compressor strangeness

I have 2 AC units in my condo (indoors, in a closet), and one of them is flakey. The electronics work ok (there's an LED status display), but *sometimes* when the compressor kicks on, the compressor doesnt start. It works sometimes; it seems to work after it's been off a while, but when it's cycling on and off it will stop working. I see the status light come on, the relay sparks; but the compressor doesnt start.

Sometimes I get a double spark when it doesnt come on.

What could be the problem?
 
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  #2  
Old 02-22-18, 04:11 PM
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It's possible that it's something as simple as a bad capacitor. Most compressor/condenser units (the unit that is normally outdoors) use a capacitor for the compressor and one for the condenser fan. Sometimes they're separate capacitors, othertimes both capacitors are in one unit (dual capacitor). The larger value capacitor is normally the one used by the compressor.
 
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Old 02-22-18, 04:14 PM
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I've replaced both capacitors in the last 5 years; I have one for the fan and one for the condenser. But I've never had it work *sometimes* before. Do capacitor get flakey when they're bad or do they just not work?
 
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Old 02-22-18, 04:25 PM
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The capacitor can become weak. Since it seems to work ok when the compressor is off for a while but not start when hot.... the capacitor would be the first thing to change.
 
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Old 02-22-18, 04:27 PM
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Ah. I get it. It needs more time to charge when it's bad! Trying to learn!
 
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Old 02-22-18, 04:42 PM
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Originally Posted by CindyFixIt View Post
Ah. I get it. It needs more time to charge when it's bad! Trying to learn!
Actually, I believe it's more a function of the system pressure. When the A/C is running, the system builds pressure, which slowly dissipates when the system is off. When the system is off for a long time, the pressure drops to its minimum value which makes the compressor easier to start.
 
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Old 02-22-18, 04:44 PM
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Thanks Bob. I didn't fully clarify my reply.
 
  #8  
Old 02-23-18, 06:44 AM
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Hi guys!

I have a 35uf 440V and a 145-174uf 220/250V capacitor. Can you tell me what the function of each of them are? I guess one starts the fan and the other kicks the compressor?
 
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Old 02-23-18, 08:09 AM
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35uf 440V is the fan run capacitor.
145-174uf 220/250V is the compressor start capacitor.
 
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Old 02-23-18, 08:14 AM
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Might be a starting cap. and a run cap. with those numbers.
 
  #11  
Old 02-23-18, 08:15 AM
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Could also be a bad contactor, or bad wiring dropping voltage to the capacitors & the compressor. .
Call a contractor & have them troubleshoot all the circuits.
 
  #12  
Old 02-23-18, 01:56 PM
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Well it wasn't the start cap. The heat pump works, but the for A/C it just clicks on, then off. Can't call anyone until Monday! HELP!
 
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Old 02-23-18, 02:43 PM
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What does the fan do during this problem ?

The heat pump and the A/C are the same thing. Both use the same compressor, same starting components, same contactor. The only difference is the reversing valve is energized in the cooling mode.
 
  #14  
Old 02-23-18, 04:07 PM
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The fan works normally.

1) When the thermostat triggers, the fan comes on, and about 20 seconds later the compressor kicks. The fan stays on regardless of what the compressor does.

So the next time it came on it did the same thing; When the compressor tried to start, there's like a double click, a spark, and the compressor doesn't start.
 
  #15  
Old 02-23-18, 04:58 PM
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More Info:

So this time, I got a double click and the compressor came on:

1) compressor kicked, contactor relay engaged
2) A spark and the contactor disengaged
3) another click and the contactor engaged and the compressor came on
 
  #16  
Old 02-24-18, 09:21 AM
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It's strangely working all day today. Came on about 5 times. I fiddled with the contactor last night. Maybe that had something to do with it?

Could a thermostat cause a problem like this? I installed a Nest on my other thermostat and I was moving this one before installing a second Nest when this started to happen.
 
  #17  
Old 02-24-18, 11:48 AM
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The thermostat shouldn't cause this type of problem. The thermostat tells the condenser/compressor and blower units to turn on/off. Since the compressor fan is coming on consistently, even though the compressor is intermittent, it's not a thermostat issue.
 
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Old 02-24-18, 11:59 AM
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Normally one contactor controls fan and compressor at the same time.

That may be a higher end unit that uses a fan contactor and a compressor contactor. Can you post the model number of the condensor ?
 
  #19  
Old 02-24-18, 12:55 PM
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I don't see that the fan is on a contactor at all. The compressor contact definitely isn't engaged when the fan is on, and it's a single contact. Been working all day. Luckily its not too hot out.
 
  #20  
Old 02-25-18, 05:17 PM
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Many water source heat pumps have an ECM blower motor.
High voltage power to the blower motor is always present and a low voltage signal controls fan operation.

Most of these “Geos” have a trouble code output LED.
It is often possible to bring up past trouble codes.

Post the make and model number of your unit for better assistance.
 
  #21  
Old 02-26-18, 01:12 PM
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It's a Trane GEVB03011J0210TLD01

There's no digital LED. There are 3 LED lights that show status, and everything works normally, except the contactor doesn't stay in contact *sometimes*. It worked all weekend and up until 10 minutes ago. What happens is that when the circuit board kicks the contactor, it sparks and doesn't stay in contact. Meanwhile the status LEDs show that it's in a normal compressor cycle; except the compressor isn't running. I can push in the spring on the contactor and the compressor runs. I cycled it again and it worked, this time with a double click, like it was trying again after it didn't start up the first time.

The issue is that it's not smart enough to know that the compressor isn't actually running. So the compressor cycle stays on forever with no cooling, requiring manual intervention.
 
  #22  
Old 02-28-18, 04:00 PM
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Ok, I've got it down to this:

The contactor doesn't engage maybe 1 out of 20 times. I can just push it in and it runs as usual. Everything else seems to run as expected.
 
  #23  
Old 03-02-18, 09:34 PM
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Does it continue to run after you remove your finger?

I see a high pressure switch , a low pressure switch, and a heat pump lockout relay in the diagram.
It looks like the contactor will lock out if either pressure switch trips.

 
  #24  
Old 03-03-18, 01:18 PM
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Sometimes it stays down, and sometimes not. When it doesn't, I noticed that I don't have the 26V to the contactor.

I was going to test the circuit board voltage and I accidentally touched the ground pin on the board and the compressor fired up. Every time it doesnt fire, I can just knock the ground wire with a wooden spoon and it fires up. Bad connection on the board?

Is that ground to the board or off the board?

 

Last edited by CindyFixIt; 03-03-18 at 01:50 PM.
  #25  
Old 03-03-18, 01:58 PM
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That's probably a ground to that board. Is there a part number on that board ?
 
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Old 03-03-18, 02:11 PM
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Axiom AF1706. Discontinued, of course.
 
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Old 03-03-18, 02:24 PM
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I'm on the road so my access is limited right now. That ground wire looks like it supplies the common 24vac to that board. You should be able to follow it to its connection point. It may go to a screw on the frame.

I would turn the power off to the unit.... pull the board off without unwiring it and check the solder on those pins.
 
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Old 03-03-18, 04:04 PM
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TB1-1: 24VAC.
TB1-2: ground (common)

Those two terminals are the power to that board are important.
 
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Old 03-04-18, 10:05 AM
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I would check for 24 volts on 1TB1-5 on that compressor lock out relay after lockout has occurred.
 
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Old 03-04-18, 10:59 AM
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What is 1TB1-5? I dont see that anywhere. Note that it's been working since I re-seated the connector. Do the contacts on these need to be cleaned?

I'm remembering why I stopped using photobucket.
 

Last edited by CindyFixIt; 03-04-18 at 11:26 AM.
  #31  
Old 03-04-18, 11:25 AM
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Can you see the picture that I posted?

How about the 1K5 HP Lockout relay?

I grew up calling these compressor lockout relays.

Looks like this one has a normally closed circuit to the contactor and a normally open circuit to the Fault line 1TB1-5.
 
  #32  
Old 03-04-18, 12:05 PM
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Not really. its too small on the screen and photobucket is asking for money. Not that I can read a schematic anyway.
 
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Old 03-04-18, 12:13 PM
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The pictures you SEE are compressed but the large file size is stored here. Either save the picture or right click on it and select "view picture" for a full size view.

Those connections visually look fine. I'd imagine the problem is defective solder on the back of them. That's what you need to check.
 
  #34  
Old 03-04-18, 12:43 PM
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right click view image redirects to photobucket. The src is on photobucket. Believe me I tried. I went into geriatric viewing mode and I can see it, but I still dont know where it is that I'm supposed to test.

It's come on about 12 times today every time.I put a new connector on with a bit of a snugger fit.
 

Last edited by CindyFixIt; 03-04-18 at 03:29 PM.
  #35  
Old 03-04-18, 04:00 PM
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Trane diagrams arenít very good anyway. It doesnít tell you what color wire connects to this control.

Climatemaster and Waterfurnace have better diagrams.
 
  #36  
Old 03-05-18, 07:52 AM
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It's also a questionable installation. I went to the local CAP shop with my compressor run capacitor and they told me that the unit wasn't even supposed to have a run cap! They said these units probably weren't designed to go into high rises.
 
  #37  
Old 03-05-18, 04:04 PM
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2 full days now without a hitch. It sure looks like it was the ground connection.
 
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Old 03-05-18, 04:36 PM
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That is great news 😃.

I saw 3 phase and single phase diagrams for that unit in the manual.
The single phase would require a run capacitor.
The single phase also had a PSC blower motor which also uses a run capacitor.

Trane Water source heat pumps are a little less service friendly.
I am impressed with your skills.

I have seen techs walk away from WSHP units.
We have customers two hours out of town that call us because no one wants to service their unit.
 
  #39  
Old 03-06-18, 05:16 AM
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It's funny. With all the multimeters, diagrams and tips I ended up finding the problem with a fat finger hitting a connector by accident. The old screwdriver in the radio trick.

I'm wondering about my CAP guy now; he said he worked at Trane for 20 years so i assumed he knew what he was talking about. He told me the wrong cap was in the unit; a Copeland 145-174 250V with a bleed resistor. Is that the correct one? The original one is metering to 140uf so I assume that is still good? Having a spare for $11 is never a bad thing!
 
  #40  
Old 03-08-18, 08:45 AM
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grounds

always double check your grounds, first thing i check when testing
 
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