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unusual AC failure mode (home, not car) #4542571
10/13/17 07:16 PM
10/13/17 07:16 PM
Joined: May 2003
Posts: 6,614
southeast US
friendly_jacek Offline OP
friendly_jacek  Offline OP
Joined: May 2003
Posts: 6,614
southeast US
I'm a bit stumped. You turn central AC on and it works OK the whole cycle, but when it cycles off and back on again, only warm humid air comes from registers forever. Condenser fan works but compressor is not running. Then I turn the system off again, restart and it works great but only for one cycle. It has been doing it for a second day and it's too dark to troubleshoot after work. Could low refrigerant do it?. I had a slow leak many years ago and fixed it, but don't remember doing the same thing, just weak cooling then. This is old unit with no fancy controls, but there is a control board that shows OK light on. Contactor and caps look OK and were replaced in the last 1-2 years. Starting relay replaced this spring. I guess it could be that.

Thanks!

PS: there is no need for AC this time of year, but this year is clearly not normal.

Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542591
10/13/17 07:28 PM
10/13/17 07:28 PM
Joined: Oct 2009
Posts: 3,510
Wet side WA
JohnnyJohnson Offline
JohnnyJohnson  Offline
Joined: Oct 2009
Posts: 3,510
Wet side WA
Is it a heat pump or just an AC?


2004 Corolla 126649
Out: VML 5w-30 TG4967 OCI 5007 Miles
In: EDGE EP 5W-30 Bosch 3311 122537 7-18-18
2006 Duramax 74478
Out: T6 5W-40 M1-303
In: T6 5W-40 XG9100 73705 4-22-18
Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542598
10/13/17 07:34 PM
10/13/17 07:34 PM
Joined: Dec 2003
Posts: 9,920
Florida, Cape Coral
Eddie Offline
Eddie  Offline
Joined: Dec 2003
Posts: 9,920
Florida, Cape Coral
Low on Freon would be my guess. When the system turns off after the first cycle the pressure side is to0 low and the sensor stops the compressor. When you restart it later the pressures have equalized somewhat and this allows another cycle. Ed


CX5 Touring 2.5L :-)
Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542743
10/13/17 10:23 PM
10/13/17 10:23 PM
Joined: May 2003
Posts: 6,614
southeast US
friendly_jacek Offline OP
friendly_jacek  Offline OP
Joined: May 2003
Posts: 6,614
southeast US
It's heat pump alright. I'll check state of charge tomorrow.

Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542750
10/13/17 10:46 PM
10/13/17 10:46 PM
Joined: Aug 2008
Posts: 21,228
ON, Canada eh?
StevieC Offline
StevieC  Offline
Joined: Aug 2008
Posts: 21,228
ON, Canada eh?
Could it be a faulty reverse valve or the thermostat not holding it in the right mode?


'18 Dodge Grand Caravan GT - AMSOIL SS 5w20
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF
Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542943
10/14/17 07:25 AM
10/14/17 07:25 AM
Joined: Oct 2005
Posts: 7,094
Colorado
Kuato Offline
Kuato  Offline
Joined: Oct 2005
Posts: 7,094
Colorado
Could be lots of things...this happened to me and it was a bad compressor - it would work fine, but got hot and for the second compressor cycle it would not turn.

Time for an HVAC guy to take a look; I hope you don't need a whole new heat pump!


Thick vs Thin test: 15k / 43k miles complete
Re: unusual AC failure mode (home, not car) [Re: friendly_jacek] #4542977
10/14/17 07:56 AM
10/14/17 07:56 AM
Joined: Apr 2015
Posts: 69
Saint John,IN
Highboy Offline
Highboy  Offline
Joined: Apr 2015
Posts: 69
Saint John,IN
Could be a bad start/run capacitor. Easy to change. You can get a new one on Amazon or eBay for 10 or 15 bucks. Lots of YouTube videos on how to do it.


2006 Scion tC PP/Denso
2008 Scion tC MaxLife/Fu
2008 Toyota Highlander Pennzoil Ultra/ Oem filter
2012 Hyundai Sonata Castrol Magnatec 5w30 /Oem filter
Re: unusual AC failure mode (home, not car) [Re: Highboy] #4543167
10/14/17 11:50 AM
10/14/17 11:50 AM
Joined: May 2003
Posts: 6,614
southeast US
friendly_jacek Offline OP
friendly_jacek  Offline OP
Joined: May 2003
Posts: 6,614
southeast US
Originally Posted By: Highboy
Could be a bad start/run capacitor. Easy to change. You can get a new one on Amazon or eBay for 10 or 15 bucks. Lots of YouTube videos on how to do it.


Thanks, but I replaced caps on this unit a few times and it's not that. Looks like it's low on refrigerant, but I'm not 100% sure as the temps are jumping around and I misplaced good thermometer. I went ahead and ordered R290 and will see what happens.

Thanks all for replying.

Re: unusual AC failure mode (home, not car) [Re: Highboy] #4544054
10/15/17 11:48 AM
10/15/17 11:48 AM
Joined: May 2003
Posts: 6,614
southeast US
friendly_jacek Offline OP
friendly_jacek  Offline OP
Joined: May 2003
Posts: 6,614
southeast US
Originally Posted By: Highboy
Could be a bad start/run capacitor. Easy to change. You can get a new one on Amazon or eBay for 10 or 15 bucks. Lots of YouTube videos on how to do it.


Actually, you were righ and I was wrong. It was a start cap that was partially failing (weak). This is what happened. I found my good thermometer and realized it was only slightly low on freon. I guess the stop leak I used 7 years ago worked. Then I swapped start relay and no change. Then I swapped start cap and it fixed it. It looked fine and it was only 6 months in service. Cheap Chinese junk I guess. My unit keeps pressure up when thermostat calls for end of cooling. Then compressor could not start against that pressure with weak cap. Turning the system off equalize pressure and helps start compressor. I learned something new. I like fixing AC and this is why I keep those 21 year old units (2 of them almost identical).


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