Intermittent AC Problem

[RDY4WAR]

I'm having a problem with my AC at my home. It'll work well and then suddenly stop blowing cold air. The condenser will still be on, fan blowing, but only room temperature air coming from the vents. It'll quickly shoot up to 80+ in the house. Then it'll start randomly blowing cold air again. When it does this, turning the AC off and back on at the thermostat doesn't fix it. Flipping the breaker off and back on doesn't fix it. It just has a mind of its own. It'll do this once or twice and then operate flawlessly for a few days. It's very unpredictable.

Any clue as to what might be causing this? I may just call a guy to come look at it, but my luck it won't be doing it when he's here.

 

[AandPDan]

Is the evaporator icing up? Might be low on charge.

 

[KJSmith]

Can you hear the compressor running when its not cooling? Is the condenser fan blowing hot air?

The two thoughts that come to mind, is the T stat randomly turning on heat or the compressor shutting down on thermal overload.

If the compressor is shutting down, they generally stay off for a while.

One easy thing for most people to check is see if the large line is sweating back all the way to the compressor.
The sweat line should stop right there ( the whole compressor should be dry).

That indicates a correct charge as a rule of thumb.

If that looks ok, then I would look at the capacitor.
If it looks swollen or oily that can be a issue.

A lot of electrical stuff comes from China. The capacitors are horrible.

This is all assuming you don't have tools and can just do visual checks.

 

[KJSmith]

Originally Posted by AandPDan
Is the evaporator icing up? Might be low on charge.


Also a good thought.

Most of the time when one ices up you don't get any air out of the vents.

 

[Cbst09]

This sounds like you may be low on refrigerant. Try turning your ac off with the "fan only" on for a few hours. This will defrost your evaporator coil. If this resolves the issue and your ac begins working again then your system is probably low on refrigerant. If low you can add refrigerant but the underlying issue will still need to be resolved at some point since you probably have a small leak somewhere (most likely the evaporator coil).

 

[RDY4WAR]

It's not icing up. That was the first thing I checked. My condenser, capacitor, accumulator, and fan are all in one big unit (Goodman). I can hear it kick on when I turn it on. It's not dirty inside and it has a new, clean filter. I'll have the refrigerant checked.

It also does this regardless of ambient temperature or how long it's been running that day. It's completely random. I usually keep the AC on 76 during the day and 72 at night. It did it to me tonight for about 2 hours and just started blowing cold again about 15 minutes ago. It was 74*F outside and 80*F in the house. Turning the AC off for over an hour before turning it back on didn't work. It seems to just start blowing cold when it wants to. The air coming out of the condenser and out of the vents are both room temperature. I haven't noticed any kind of clicking or engaging sound when it starts blowing cold again, nor when it decides to stop. Usually I don't know that's happened until I start feeling warm and go feel the vent.

 

[JMJNet]

I have case like yours, the capacitor still looks good (not bulging) but when I measure the capacitance was not up to spec (1 or 2 uF).
That cause it to still run but give intermittent issue.

Another issue can be the contact on the switch.

 

[greg_J35]

As a 30 year HVAC technician, I have seen what you are describing be corrected by replacing the compressor contactor and capacitor. I have also noticed that Goodman equipment begins to have component failures after about four years of operation.

 

[vwmaniaman]

How about expansion valve problem? If the lines back to the unit are dry and no cold air maybe valve sticking open.

 

[bubbatime]

I have a Goodman that is doing the exact same thing. Technician said it was low of Freon and charged it back up, in which case it started working fine again. He also said he changes more bad coils on these Goodman units than any other brand. My house is only 3 years old and needs the coil replaced already.

I think Goodman has a terrible reputation in the industry and doesn't last long.

 

[wag123]

Originally Posted by JMJNet
I have case like yours, the capacitor still looks good (not bulging) but when I measure the capacitance was not up to spec (1 or 2 uF).
That cause it to still run but give intermittent issue.
Another issue can be the contact on the switch.

Originally Posted by greenfordtruck
As a 30 year HVAC technician, I have seen what you are describing be corrected by replacing the compressor contactor and capacitor. I have also noticed that Goodman equipment begins to have component failures after about four years of operation.
I would go ahead and replace the capacitor. Capacitors tend to fail and they are cheap (under $20). The newer dual-sided capacitors only seem to last about 5 or 6 years. I keep a spare because of this.

 

[Mackelroy]

On the outside unit, theres the fan, but the compressor pump also has to be running, the capacitors can fail and the compressor will not run, maybe intermittently, if cap is weak.

 

[RDY4WAR]

Originally Posted by bubbatime
I have a Goodman that is doing the exact same thing. Technician said it was low of Freon and charged it back up, in which case it started working fine again. He also said he changes more bad coils on these Goodman units than any other brand. My house is only 3 years old and needs the coil replaced already.

I think Goodman has a terrible reputation in the industry and doesn't last long.


I've got somebody coming out to look at it on Monday. This unit is 5-1/2 years old and had to have the fan motor replaced about a year ago. I don't think I'll own another Goodman.

 

[Yah-Tah-Hey]

Originally Posted by AandPDan
Is the evaporator icing up? Might be low on charge.

Next time this occurs remove the air handling unit access panel and look at the evaporator. If its frosted over you have your answer-low refrigerant charge.

 

[zzyzzx]

Originally Posted by greenfordtruck
As a 30 year HVAC technician, I have seen what you are describing be corrected by replacing the compressor contactor and capacitor.


I prefer to diagnose over taking the shotgun approach.
For all I know, they got ants in their contactor, but that won't make a capacitor go bad.

 

[wag123]

In Texas we now have something called crazy ants. They are the worst kind of ants about getting into electrical devices, and they even eat insulation. They are giving the electric utilities fits. I have had them foul my contactor before. When my contactor is fouled by them neither the compressor or the condenser fan will run. For me, that has been the dead giveaway that the contactor needs attention. Otherwise, when one motor or the other won't run, I just change the capacitor, and that has always solved the problem.

 

[EA82]

Sounds like the compressor may be cutting out, there could be many reasons for this but one is that it goes out on high pressure switch or internal overload and once it cools off the compressor starts running again. Just my guess obviously , how old and what brand is the unit ? is the condenser coil dirty ?