I just realized that my home heat pump compressor keeps running
and freezing the line by bypassing the thermostat. I believe the
thermostat itself is still in good working order because if I set it
to a temperature lower than the outside temperature, compressor and
condenser fan come on, and when it reaches the preset temperature, the
condenser fan stops spinning while the compressor keeps working and
freezing the line. Any idea of what is wrong?
Thanks in advance for any help/suggestion.
Maybe I didn't explain the problem clearly enough. I meant to say that
no matter what the temperature setting of the thermostat inside the
house is, the compressor will still run, while the condenser fan will
stop once the preset temperature inside the house is reached.
Basically the compressor does not respond to the thermostat setting,
while the condenser fan does, and as soon as the fan stops spinning, I
see ice forming around the line that goes inside the house to the
evaporator. This is what I meant by saying "bypassing the thermostat".
I agree with you about the nature of the problem, and I was hoping
that somebody else had experienced something similar and could be
more specific about what to look for.
Please excuse the alt.hvac resident idiot... he knows just enough about HVAC
to be dangerous to anyone that *will* listen to him. But rest assured, he'll
As you know, that makes up for everything he lacks to be an excellant HVAC
Now getting to your problem...
I want to clearify some things that people often get mixed up about.
The outside unit "condenser" contains the compressor and condenser fan.
The indoor unit "evaporator" is either installed with an air handler or
So in your case, is it the indoor or outdoor fan that stops running?
I would guess that you mean the indoor evaporator motor stops running. While
the complete outdoor unit continues to run, including the condenser fan.
Either way, this problem should be looked at by someone that has the proper
training and tools to repair your unit.
While they are there, have them service your unit to insure its running
efficiently. As there's no need to waste money on operational cost.
What occurs to me. When the outdoor unit shuts off, the condensor still
contains high pressure refrigerant, liquid at the bottom of the condensor.
So, it's possible if the condensor fan and compressor shut off, you can
still have refrigerant migration, due to the pressure difference.
Makes me wonder if you have a clogged filter dryer, in the outdoor cabinet.
Or near the discharge valve. Could be that the filter is acting as a
If the compressor continues to run, that's a puzzler. How would the
compressor continue to get powered, after the contactor opened? Sounds like
you have a wiring problem, or a switching and controls problem.
I'd be curious what brand unit you have.
Some of the old GE's & Tranes use separate poles on the contactors so
its possible for the compressor to run without the fan if the contractor
goes bad or sticks like pjm noted.
The freezing up on the line just doesn't make sense unless you're talking
about a very short time after the fan shuts off & then it goes away.
You could have two problems where the gas is low also.
Either way you should have called someone by now.
The compressor staying on is a simple problem to fix but you don't want to
make it into a bigger one.
I see your point & I don't ever remember running into a scenario like
this one but something doesn't sound right. I've seen it plenty of
times when the contactor sticks, the blower shuts off & the system will
freeze up. I would think that the condenser fan not working would create
high enough pressure to keep the suction line over the freezing
temperature if fully charged. With the indoor blower not working that
would help cool things down but I wouldn't think enough to freeze for any
extended period of time because I think the head pressure would start to
cancel it out as it builds. That's why I'm wondering if the gas could be
low also along with a stuck contactor.
That's really strange. On the central AC units I've serviced, the condensor
fan and the compressor are on the same relay, so they turn on and off at the
same time. If the condensor fan turns off, then the compressor would
overheat, in very short ammount of time. I had to replace an outdoor unit
one time, for a guy whose condensor fan would run only if he pushed it with
You're really showing your ignorance the last few days...
Compressors don't rely on the condenser fan for cooling purposes!
I suppose you never saw a Rheem unit were the compressor is to the
On Thu, 19 Jun 2008 10:57:40 -0700, alexpio wrote:
I'm just guessing but it sounds like you're confusing the condenser fan
with the inside evaporator fan. It would be very unlikely for the line to
freeze if your outside condenser fan wasn't running unless you were
running in heat mode & the indoor fan was running. You really need to call
a pro before something more serious happens to your system.
On Jun 19, 1:57 pm, firstname.lastname@example.org wrote:
OK, I fixed it. I want thank everybody for your help in solving the
problem. As .p.jm@see_my_sig_for_address.com suggested, it was a
welded contactor. I replaced it, and the ac is running beautifully!
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