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any hvac/heat pump experts here? #4596716
12/07/17 01:46 AM
12/07/17 01:46 AM
Joined: Apr 2003
Posts: 350
austin, texas
mikeinaustin Offline OP
mikeinaustin  Offline OP
Joined: Apr 2003
Posts: 350
austin, texas
i have a 7 year old carrier heat pump. tonight was the first night cold enough to turn heater on (about 40 outside). by chance, i happened to be near the outdoor unit when it came on. it turned on and fan spun for about 10 seconds then shut off for 5 seconds then back on, etc. i then turned thermostat way down and attempted to get it to output cold air instead of heat. this worked fine, the unit outside turned on and stayed on, no problems at all. i then retested heat mode and it once again started short cycling.

any ideas?

Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4596797
12/07/17 07:53 AM
12/07/17 07:53 AM
Joined: Nov 2011
Posts: 4,857
MTL, CANADA
Rolla07 Offline
Rolla07  Offline
Joined: Nov 2011
Posts: 4,857
MTL, CANADA
I would try resetting the breaker and see if it somehow resets itself. As long as you set a temp indoors that is high enough (higher than indoor ambient air, it should work. Im not a hvac tech though.


2007 Corolla Red Pearl 155k miles
PP 0w20 & ST 4967

Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4596804
12/07/17 08:03 AM
12/07/17 08:03 AM
Joined: May 2007
Posts: 7,509
Indianapolis, IN
dnewton3 Offline
dnewton3  Offline
Joined: May 2007
Posts: 7,509
Indianapolis, IN
It's hard to diagnose from several states away.

Which of the two motors was coming on and going off? Fan or compressor? Or both?

If the compressor is coming on and staying on, and only the fan is cycling, it could be a motor problem (thermal overload tripping in the motor itself).
It could be a system problem (pressure switch not sensing, or low refrigerant for the HP cycle).
It could be a host of other small things.

I realize that's not what you want to hear; makes it hard to DIY this problem. But it's not easy to troubleshoot without being there to poke and observe.


The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money
Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4596827
12/07/17 08:32 AM
12/07/17 08:32 AM
Joined: Mar 2004
Posts: 20,760
Upstate NY
Donald Offline
Donald  Offline
Joined: Mar 2004
Posts: 20,760
Upstate NY
The electric booster coils are in the air handler inside the house. You need an HVAC guy with a schematic. The heat pumps are sophisticated units. There is also some defrost that happens. Maybe that's happening.


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4596879
12/07/17 09:35 AM
12/07/17 09:35 AM
Joined: Sep 2015
Posts: 1,531
USA
mk378 Online content
mk378  Online Content
Joined: Sep 2015
Posts: 1,531
USA
In a defrost cycle, the compressor runs with the reversing valve in the cooling mode (to pump heat outside and thaw the outdoor coil) with the outside fan stopped. Also the electric heaters inside are turned on so cold air doesn't come from the vents in the house. This should only happen for a few minutes at a time then it will switch back to pumping heat inside.

Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4596934
12/07/17 10:12 AM
12/07/17 10:12 AM
Joined: Oct 2007
Posts: 577
TN
TTK Offline
TTK  Offline
Joined: Oct 2007
Posts: 577
TN
What he described is not the defrost cycle. A defrost cycle does not turn on and off like that. When it turns on it continues for the prescribed time( usually a few minutes) then reverses back to heating. May be a reversing valve issue.

Last edited by TTK; 12/07/17 10:14 AM.

2010 Volvo V70-3.2
Current Fill:Castrol Magnatec 5w-30
2018 Subaru Forester, 0w-20 Subaru oil
2001 Chevrolet Prism:Castrol Magnatec 5w-30

Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4597176
12/07/17 03:02 PM
12/07/17 03:02 PM
Joined: Apr 2003
Posts: 350
austin, texas
mikeinaustin Offline OP
mikeinaustin  Offline OP
Joined: Apr 2003
Posts: 350
austin, texas
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work. cooling would have started to short cycled too as more refrigerant was lost over time.

Re: any hvac/heat pump experts here? [Re: mikeinaustin] #4597453
12/07/17 08:27 PM
12/07/17 08:27 PM
Joined: Feb 2013
Posts: 10,719
Phoenix, AZ
Nick1994 Offline
Nick1994  Offline
Joined: Feb 2013
Posts: 10,719
Phoenix, AZ
Originally Posted By: mikeinaustin
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work. cooling would have started to short cycled too as more refrigerant was lost over time.
Where did the refrigerant go?

I too have a Carrier heat pump. 6 years old and A/C wasn’t cooling that well this summer. Turns out the evaporator is leaking. 10 year warranty on parts so I’m working on that.


2015 Hyundai Sonata 2.4L 84k Mobil 1 AFE 0w30 & OEM
2000 Toyota Camry 2.2L 230k Valvoline 5w30 & Fram Ultra
1996 Jeep Cherokee 4.0L 147k Mobil 1 HM 10w40 & Fram Ultra
Re: any hvac/heat pump experts here? [Re: dnewton3] #4597591
12/07/17 10:52 PM
12/07/17 10:52 PM
Joined: May 2007
Posts: 7,509
Indianapolis, IN
dnewton3 Offline
dnewton3  Offline
Joined: May 2007
Posts: 7,509
Indianapolis, IN
Originally Posted By: dnewton3
... or low refrigerant for the HP cycle).


Originally Posted By: mikeinaustin
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work.


Well maybe I was a bit more accurate in diagnosis than I first imagined!

Glad it's working now.


Last edited by dnewton3; 12/07/17 10:53 PM.

The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money

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