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Discussion Starter #1 (Edited)
My GOODMAN GSZ140421KA HVAC UNIT (MFG. OCT 2015) stopped blowing cold on Thursday.

I called the largest HVAC outfit in my hometown for a troublecall. Its 90 degrees out.

Tech arrives next day. Tells me to turn off the unit (from my phone, I have a nest controller) He hears the compressor "humming" trying to kick on, then quits. repeats a couple times. Using a clamp, he tests the line and its "drawing 10 amps" during the 'humming' periods. He installs a (presumbably used) run/start capacitor from his truck into the unit. No change. He also notes some brown heat marks on the defrost board.

Written Diagnosis: Failed compressor & degraded defrost board. $2200 to replace.

???

I request and pay for a second opinion from the second largest outfit in town.

It's saturday now. Same process, only now this new tech's (presumably used) capacitor starts the compressor (!) but the shroud fan still won't turn. I suggest we bump the fan blade with a stick? He agrees. The fan comes up to speed. Unit blows cold. House now back down to high 70's. Nice! (NOTE: This time my unit was cold from being left off a full day)

His Diagnosis: Bad Fan- orders $110 fan to arrive tuesday. Says the cap is fine.

Something still doesn't seem right to me. He insists the used cap he leaves in the unit is fine (even though it needs to be bumped to start the fan - not kidding)

Frustrated that I got what seems like two bad diagnosis/techs, I read up on hvac (I was a navy radar tech, never an HVAC tech) and refresh my memory on how to test fan motors and capacitors.

I ohm out the fan. Heres the readings:
Black to Purple: 29.1
Black to Brown: 66.7
Purple to Brown: 94.1
So, 1 to 2 ohm off.
My understanding (based on some youtube videos) is if Bk2Pu+Bk2Br=Pu2Br or very close, then the fan is good.
None of the 3 terminals show shorted to capacitor exterior btw.
Also, FAN spins freely when not energized. I feel, hear, see no signs of bad/degraded bearings. I think the reason the fan didn't work for the first tech was it was overheated and was in overtemp shutdown mode.

Capacitance Readings on the 5/45uF 440V dual capacitor.
Common to Fan:0 uF (instead of 5uF +/-5%)
Common to Herm: 28 uF (Instead of 45uF +/- 5%)

MY diagnosis: Bad capacitor (no doubt), fan is fine (?)

Two questions:
1) IS MY FAN BAD ALSO, BASED ON THE SYMPTOMS AND READINGS GIVEN?
2) I ordered a new cap off Amazon. Fan and Cap dont arrive till tuesday (its sunday). CAN I SAFELY RUN THE AC WITH A CAPACITOR THAT READS 0uF/28UF VS 5uF/45uF if I just bump start the fan, and let it to cool all day. ( Ill shut it off at night) Will this damage my unit in any way?

Thank you!
 

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Sounds like a dead capacitor. This should have been easily verified via the techs there. They didn’t test the capacitor?
 

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You need the full 45uF to start the compressor. Now it is drawing a lot more amps at start and that is very hard on the windings.

I would not do it or you may damage the windings and short it out and wreck the compressor.

You may also overheat the compressor to the point it cuts out on the internal temp overload and that can take 12 hours to reset and is a bad place to get to.
 

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Discussion Starter #4
Sounds like a dead capacitor. This should have been easily verified via the techs there. They didn’t test the capacitor?
Nope. He's tunnel visioned into thinking only the fan is bad. Today I texted him the capacitance readings of the cap. No reply from him. i think he knows he messed up and has gone sinker. I just want to know if I will damage my unit using this degraded capacitor till tuesday, and if the winding readings i took confirm my fan is fine.
 

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Discussion Starter #5
You need the full 45uF to start the compressor. Now it is drawing a lot more amps at start and that is very hard on the windings.

I would not do it or you may damage the windings and short it out and wreck the compressor.

You may also overheat the compressor to the point it cuts out on the internal temp overload and that can take 12 hours to reset and is a bad place to get to.
Ok. Im going to turn off my unit then until the new cap arrives. Whats your opinion of the fan based on my findings. Good? Degraded? Bad?
 

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Discussion Starter #8 (Edited)
Managed to find a tech who'd meet me on the side of the road to sell me a 45/5 Cap out of his truck on a Sunday. :vs_OMG: Very lucky and grateful.

Checked capacitance levels (45.32uF/4.945uF) and Installed it. As expected, system booted right up.

Now the wait to see if the system has been blowing good capacitors in hours/days, or if two separate techs from two mainstream companies troubleshot off of two broken capacitors.

My other theory is first guy used a good capacitor but forgot to check/confirm the system was in overtemp lockout mode - and just assumed that since it didnt boot up, must have been a blown compressor. To think I was this close to telling them to go ahead and do it.

Side question: Is it normal, professional to rule a compressor bad without testing it with a megger? Is that super specialized equipment/procedure or something?
 

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Is it normal, professional to rule a compressor bad without testing it with a megger?

Sorry to be a cynic, but it's SOP for some companies to convince you that you need whatever makes them the most money, sometimes by whatever means they think they can get away with, even using a bad or incorrect cap to 'prove' it to you. Good for you (and your bank account) that you were willing to check it for yourself.
 

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I called the largest HVAC outfit in my hometown for a troublecall. Its 90 degrees out.

I request and pay for a second opinion from the second largest outfit in town.

The diagnosis was improving as the company size diminished, you might be on to something. Good job, hope the new cap solves the problem.
 

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If it had overheated there is a high temp limit switch buried in the windings which would be open. You can determine that by checking for continuity between the windings and don't need a megger.

Plus the top of the compressor is usually so hot you cannot touch it for long. Cannot hold your hand on it.

IMO your problem is likely just a bad capacitor. Buy a spare one as they are all made cheap in Asia and not like the old days when they lasted 4ever.
 

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Owner operators are more likely to know the trade better. Apparently those big companies don't vet their hires too well.

I agree, the fan motor has probably not been damaged and neither has the compressor. The formvar or equal insulation on motor windings can stand 105° C. (221° F.) with no ill effects. That's spit fryin' hot!

Good for you for being smart enough to see the light through all the smoke screen they laid down. I suppose it helps to use radar. :vs_closedeyes::detective::1eye:

ps. Thanks for your service as a navy radar tech. and all else.
 

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Side question: Is it normal, professional to rule a compressor bad without testing it with a megger? Is that super specialized equipment/procedure or something?

I was an infantryman in the Marine Corps, all I was taught was how to throw grenades, shoot people and dig foxholes and of course shine boots.



If you can find a good tech who is not trying to maximize profits every time they show up. Treat them well, offer to wash and wax their truck, buy them dinner, send them Xmas and birthday cards ask to see pictures of their grand kids.


I may be cynical, I was not born this way, I would suggest you Google air conditioning service rip off scam videos! The largest AC company in SW Florida was recently shut down and charged with fraud!
 
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