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#4812705 - 07/12/18 09:01 PM HVAC Compressor Quit
sleddriver Offline


Registered: 02/06/10
Posts: 4704
Loc: Central Texas
Not sure if it's Tango Uniform yet....

Earlier, I heard this loud BANGING noise outside. Discovered it's coming from the outdoor unit. Turns out a two-prong plug on the fan motor came loose, got caught in the fan blade, causing the racket. {This is not the wiring running from the motor to capacitor. Not sure what it is actually...)

Reconnected then zip-tied to pvc tube carrying 3 motor wires. Turned on A/C again, outdoor fan spinning. OK..so back to work.

After awhile I notice it's getting a bit warm in the office even with a desk fan blowing on me. I look at the weather station readout: 83F inside! Indoor fan is running. Outdoor fan is not.

Pull service panel off and feel HEAT coming out! Turn off 220Vac breaker in service panel. Top of compressor too hot to touch but not burning hot either. Bottom is hotter but not burn hot. I slowly pour half a gallon of tap water on top to cool it off. Top temp quickly drops; bottom not so much.

I remove 3 wires to compressor: C (common), R (run winding), S (start winding). I measure comp. terminal resistances as follows:

C > R: Open
C > S: Open
R > S: 3.5 Ohms.

A view of the schematic reveals a thermal cutout on both S & R windings. Given the above measurements, my thinking is both windings are OK however one or both thermal cut-outs are open.

Q: Do these thermal breakers 'reset' when cooled off or are they one-shot-only?

I have a fan blowing on the compressor to aid cooling and will recheck in a bit to see if I'm lucky today.
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4812721 - 07/12/18 09:09 PM Re: HVAC Compressor Quit [Re: sleddriver]
JLawrence08648 Offline


Registered: 01/20/17
Posts: 253
Loc: NJ
The most common thing to go is the capacitor. To test, override, go to where all the wires are, there's a block, there's a type of push button that is spring loaded, push out in with an insulated screw driver, if the compressor is good, it will kick in, now replace the capacitor.

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#4812730 - 07/12/18 09:21 PM Re: HVAC Compressor Quit [Re: sleddriver]
FSully1 Offline


Registered: 11/22/14
Posts: 46
Loc: Florida
Thermal overload will reset. It may take awhile, unless you dump water on the shell of the compressor. You can also fill a large ziploc with ice and place on top of compressor shell. Check run cap and start cap(if you unit uses.)

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#4812759 - 07/12/18 10:08 PM Re: HVAC Compressor Quit [Re: FSully1]
sleddriver Offline


Registered: 02/06/10
Posts: 4704
Loc: Central Texas
Indeed they will! That's a relief!

One winding meas. 2.5 Ohms, the other 0.8. I turned the breaker back on. Meas. 247Vac on the contactor. Waiting about 15 min. for the comp crankcase heater to warm up the refrigerant before calling for cooling.

Also discovered the C terminal wiring at the compressor connection to be badly corroded. This led to overheating which had melted the insulation where the quick-connect female was. I cut this back, then crimped on a new connector for now. Looks like the old one had been arcing. Obviously, quite a bit of inrush-current flows through terminal "C" + a running current of perhaps 12A or so.

It's currently 84F inside. Looks like I won't have to sleep w/o cooling tonight!
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4812763 - 07/12/18 10:14 PM Re: HVAC Compressor Quit [Re: sleddriver]
KJSmith Offline


Registered: 08/31/15
Posts: 267
Loc: TX
If I am in a hurry, I will put a bag of Ready Ice on top.
That will cool it down fairly quickly.

No need to wait on the CCH when its that hot.
The compressor was already way hotter than the heater can make it.

If the stake on is burnt/corroded, any HVAC supply house will have a terminal repair kit.
You will be able to figure out the install.

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#4812765 - 07/12/18 10:17 PM Re: HVAC Compressor Quit [Re: sleddriver]
KJSmith Offline


Registered: 08/31/15
Posts: 267
Loc: TX
Some fan motors are reversible.
Newer ones will have short loops with yellow and orange wires.

Make sure your fan is spinning the right direction.

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#4812769 - 07/12/18 10:21 PM Re: HVAC Compressor Quit [Re: sleddriver]
Donald Offline


Registered: 03/21/04
Posts: 20547
Loc: Upstate NY
When you get much below 1 ohm it's best to get a 4 wire ohm meter to measure with.

Not sure I would go dumping buckets of water on hot HVAC components. Fan yes.
_________________________
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)


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#4812792 - 07/12/18 10:54 PM Re: HVAC Compressor Quit [Re: sleddriver]
sleddriver Offline


Registered: 02/06/10
Posts: 4704
Loc: Central Texas
Well the plot thickens...still no cooling. Though a call for cooling has been made by the t-stat, and power is enabled to the outdoor unit, it doesn't turn on.

As the motor/comp capacitor is new as of Aug 2017 (quality USA made cap), I suspected the outdoor contactor. So I pushed in on the contact with a wooden dowel and both comp & fan came to life. I let it run about 5 min. Didn't notice the pressure line getting hot however. Perhaps 5 min. wasn't enough.

I turned off the outdoor unit at the breaker box and checked the cont. coil resistance @ 15 Ohms. So it's not open, nor shorted. Next, I checked for around 24Vac on the wires going to the coil. Nothing there.

I spied a small controller board inside and checked Vac to ground. I found 30Vac on some a maybe 21Vac on others. Didn't have anything with me to write them down. So the controler board is getting power but it's not powering on the contactor.

To further diagnose, I'll need to de-wire both it and the contactor. There are several small box relays on board, perhaps one of these is TU or its driver ckt is.

This would have to go off-line around 5:30p CDT!
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4812800 - 07/12/18 11:08 PM Re: HVAC Compressor Quit [Re: sleddriver]
KJSmith Offline


Registered: 08/31/15
Posts: 267
Loc: TX
Typically you may have a time delay (small black thin square, can have 2 or 3 wires to it.
A low pressure switch connected to the bigger line, usually two light blue wires.
A high pressure switch... this can be a manual reset, connected to the smaller line, typically two red wires, reset button should be on top.

The pressure switches are inside around the compressor the timer in the electrical section.

All the above are low voltage ( 24 vac).

What brand unit?
Picture?


Edited by KJSmith (07/12/18 11:14 PM)

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#4812803 - 07/12/18 11:11 PM Re: HVAC Compressor Quit [Re: sleddriver]
CDX825 Online   content


Registered: 10/04/09
Posts: 163
Loc: Litchfield, Ohio
If your getting 24 volts to the unit but its not engaging the contactor it could be a pressure switch open if it has one.
_________________________
1984 Ford F250 6.9 Diesel C6 2WD Rotella T 15W40 NTZ Bypass Filter

1992 Ford F150 5.8 4x4 Rotella T5 10W30


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#4812810 - 07/12/18 11:31 PM Re: HVAC Compressor Quit [Re: sleddriver]
sleddriver Offline


Registered: 02/06/10
Posts: 4704
Loc: Central Texas
Unit is a Goodman 3T, made in about 1990. R-22.

I do have gauges I can hook up. I'd be very surprised if there was no R22. How could it all just leak out? I didn't hear any PSSST when putting the fan cover/lid back on and sinking the screws.

Came indoors. Upflow unit is in a small closet above return plenum so access is easy (no climbing around in a hot, humid attic...). I found the xnsfrmr inside the cabinet. Sec V = 30Vac. Pink wire. Runs to terminal block, which supplies low V outside and to t-stat (which is on & functional).

Here's a photo of the outdoor unit's electrical box:




This looks like a pressure cut-out SW (hi? low? both?). It's installed on the liquid line:
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

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#4812815 - 07/13/18 12:03 AM Re: HVAC Compressor Quit [Re: sleddriver]
CDX825 Online   content


Registered: 10/04/09
Posts: 163
Loc: Litchfield, Ohio
Could have been off on high pressure too. Something had to be going on for the compressor thermal switch to open. High head pressure I'm guessing.

Your very bottom picture shows the high side pressure switch. The small green can with the yellow wires coming out attached to the 3/8" copper line. Check it for continuity. I cant tell by the picture if it has a reset on it. Some do and some don't.
_________________________
1984 Ford F250 6.9 Diesel C6 2WD Rotella T 15W40 NTZ Bypass Filter

1992 Ford F150 5.8 4x4 Rotella T5 10W30


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#4812824 - 07/13/18 12:28 AM Re: HVAC Compressor Quit [Re: sleddriver]
sleddriver Offline


Registered: 02/06/10
Posts: 4704
Loc: Central Texas
Out came the gauges and there's no pressure.....as I was cussing my fate, I happened to look up and see this:



which resulted in this:


I'm such an idiot! Out of all of the top lid screws to pick, I happened to pick one too long and drove it right into a too-close-copper line....son of a [censored]! What are the odds of that??

I can solder the hole closed (acid flux & lead solder? I have that + MAPP torch) but will have to pay someone to draw it down then refill. Time to start shopping around for a good deal. Don't have a clue who to call either as no one else has worked on this system in roughly 15-18? yrs.

I'm going to put a piece of aluminum tape on that and call it a night....
_________________________
1998 Volvo V70 T5 226,808 mi. Original Owner.
M1 10W-30 HM
"It's never a mistake to buy tools, defined broadly. They're not a cost, they're an investment." - J.B. Peterson

Top
#4812911 - 07/13/18 06:40 AM Re: HVAC Compressor Quit [Re: sleddriver]
KJSmith Offline


Registered: 08/31/15
Posts: 267
Loc: TX
Soft solder will not hold.
Needs.


If you have it repaired, go back with MO99 or NU22 as a refrigerant.

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#4812921 - 07/13/18 06:58 AM Re: HVAC Compressor Quit [Re: sleddriver]
rshaw125 Offline


Registered: 08/18/04
Posts: 3276
Loc: Raleigh ,NC CSA
Should not cost too much. Plenty of R22 out there or use one of the many drop in replacements.
_________________________
2012 Porsche Carrera S
2016 Ford Edge 2.0
2002 Taurus Vulcan SOLD
2006 Explorer SOLD

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