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Message
re: Help me diagnose my A/C issue...condensing unit not turning on...
Posted on 5/5/16 at 12:50 pm to Chicken
Posted on 5/5/16 at 12:50 pm to Chicken
Had a very similar problem at my old house. I believe it only affected my heater though. Was a cheap relay that was out. Heater would turn on the first time no problems, but when the thermostat shut it off, it would not turn back on the heating coils the next time. Only turning on the fan.
0
Posted on 5/5/16 at 12:53 pm to Chicken
It sounds like it is freezing up and thawing itself out. This is caused from low coolant in the system.
The next time it does it, take the cover off of the inside unit and see if the coils are frozen.
The next time it does it, take the cover off of the inside unit and see if the coils are frozen.
Posted on 5/5/16 at 12:55 pm to Chicken
Could be blower motor. Just had to replace one.
Posted on 5/5/16 at 12:56 pm to Chicken
You have two motors outside, the compressor (inside the unit) and the fan (mounted to the lid, pulls air through the coils). I presume that neither one is running in your case.
Your symptoms suggest a bad tstat to me. A bad capacitor or a bad contactor would usually be more persistent and less likely to "go away" just by cycling the unit on & off although I wouldn't rule either out entirely.
Other scenario is a compressor with thermal protection that is operating. Once it overheats, the thermal overload opens and the compressor motor stops, the freon stops flowing and the house gets hot. Once it cools down, it can restart normally upon demand. Thermal protection is sometimes wired in the control circuit meaning it will stop both the fan & compressor but normally it opens the compressor motor leads and leaves the fan running.
Could also be a high head pressure switch in your refrigerant circuit. Dirty coils in your outside unit can cause this.
Your symptoms suggest a bad tstat to me. A bad capacitor or a bad contactor would usually be more persistent and less likely to "go away" just by cycling the unit on & off although I wouldn't rule either out entirely.
Other scenario is a compressor with thermal protection that is operating. Once it overheats, the thermal overload opens and the compressor motor stops, the freon stops flowing and the house gets hot. Once it cools down, it can restart normally upon demand. Thermal protection is sometimes wired in the control circuit meaning it will stop both the fan & compressor but normally it opens the compressor motor leads and leaves the fan running.
Could also be a high head pressure switch in your refrigerant circuit. Dirty coils in your outside unit can cause this.
Posted on 5/5/16 at 12:57 pm to Chicken
Check the drip pan 
Posted on 5/5/16 at 1:05 pm to LSUsmartass
quote:
Check the drip pan
This. The drip pan under the inside (attic?) air handler has a drain and a high level switch that turns off the outside unit if the water level gets too high. This will happen if the drain from the drip pan gets restricted. (Ask me how I know this.) If so, unplug the drain (I blew mine out with compressed air).
Posted on 5/5/16 at 1:07 pm to meauxjeaux2
quote:
bad Capacitor or Contactor
this.
Capacitor is like $5. Try changing that first.
Posted on 5/5/16 at 1:10 pm to reverendotis
quote:
A bad capacitor or a bad contactor would usually be more persistent and less likely to "go away" just by cycling the unit on & off although I wouldn't rule either out entirely
My thought precisely except I would likely rule out the capacitor, those almost always fail completely and permanently. Contactors can be a little flaky, particularly if there is something like an ant issue or carbon build up although even those usually get progressively worse over time.
The fact that the blower inside starts to run continuously and even keeps blowing after the thermostat is turned to off makes me think it is the control circuitry, either the thermostat or the control board on the unit itself.
Posted on 5/5/16 at 1:11 pm to lsuhunt555
Capacitor. Change yourself and profit. Easy.
Pull breaker first please.
Pull breaker first please.
Posted on 5/5/16 at 1:13 pm to meauxjeaux2
Yeah but this is chicken. He doesn't know the difference between a screwdriver and a pair of pliers.
Posted on 5/5/16 at 1:13 pm to mdomingue
quote:
I would likely rule out the capacitor, those almost always fail completely and permanently
Not a all true. When a capacitor is failing it won't deliver enough voltage to start up the condensing unit fan, but if you nudge it with your finger it'll perform fine. It'll function intermittently like that unil it finally fails.
Posted on 5/5/16 at 1:17 pm to The First Cut
quote:
Not a all true. When a capacitor is failing it won't deliver enough voltage to start up the condensing unit fan, but if you nudge it with your finger it'll perform fine. It'll function intermittently like that unil it finally fails.
not what he was saying and you evidently don't know what the purpose of a capacitor is.
Also many Condensing units have dual run capacitors. One side for the fan and one for the compressor.
Posted on 5/5/16 at 1:22 pm to The First Cut
this is note from maintenance visit:
Residential Service customer made service call because upstairs ac
was not working. Upon arrival applied demand for ac on upstairs Tstat.
System was operating as intended. While inspecting outdoor unit the 24
volts at contactor was lost. Made sure all electrical connections were
good at outdoor unit. Then went to indoor unit and made sure all
electrical connections were good. Also removed Tstat from wall to
ensure all low volt wires were in proper place. Did not find any electrical
faults. Reinstalled Tstat on wall applied cooling demand gave unit 30
minutes of run time and did not lose 24 volts again. If we are called
again by homeowner within 30 day for same issue no service fee will be
applied.
Residential Service customer made service call because upstairs ac
was not working. Upon arrival applied demand for ac on upstairs Tstat.
System was operating as intended. While inspecting outdoor unit the 24
volts at contactor was lost. Made sure all electrical connections were
good at outdoor unit. Then went to indoor unit and made sure all
electrical connections were good. Also removed Tstat from wall to
ensure all low volt wires were in proper place. Did not find any electrical
faults. Reinstalled Tstat on wall applied cooling demand gave unit 30
minutes of run time and did not lose 24 volts again. If we are called
again by homeowner within 30 day for same issue no service fee will be
applied.
Posted on 5/5/16 at 1:25 pm to The First Cut
quote:
Not a all true. When a capacitor is failing it won't deliver enough voltage to start up the condensing unit fan, but if you nudge it with your finger it'll perform fine. It'll function intermittently like that unil it finally fails.
Nudging it with your finger is actually performing the function of the start capacitor. The purpose of the start capacitor on a single phase motor is to increase the torque on startup so it gets to speed quickly. AC motors have very little torque at low speeds and single phase motors will usually not start without a start capacitor.
This post was edited on 5/5/16 at 1:41 pm
Posted on 5/5/16 at 1:31 pm to Chicken
Bad capacitor! Easy fix
Posted on 5/5/16 at 1:34 pm to Chicken
well that would have been nice to begin with.
The contactor is losing voltage to the switch side or is not able to make contact at times because of heave carbon buildup on the contacts.
If no carbon buildup then suspect the signal wire which comes from the thermostat. But before the signal is sent out to the condensing unit it must first go through the relay inside the Evaporative unit inside the home.
The contactor is losing voltage to the switch side or is not able to make contact at times because of heave carbon buildup on the contacts.
If no carbon buildup then suspect the signal wire which comes from the thermostat. But before the signal is sent out to the condensing unit it must first go through the relay inside the Evaporative unit inside the home.
Posted on 5/5/16 at 1:39 pm to meauxjeaux2
well, the odd thing is that when I turn the system completely off at the thermostat, the inside fan (blower?) will continue to run for hours.
Posted on 5/5/16 at 1:41 pm to Chicken
quote:definitely starting to sound like a control board now. Or relay. How old is the system? What brand?
well, the odd thing is that when I turn the system completely off at the thermostat, the inside fan (blower?) will continue to run for hours.
Heat pump?
Posted on 5/5/16 at 1:42 pm to Chicken
quote:
If we are called
again by homeowner within 30 day for same issue no service fee will be
applied.
What are you waiting for? Call them back out.
Posted on 5/5/16 at 1:44 pm to Chicken
quote:
Other scenario is a compressor with thermal protection that is operating. Once it overheats, the thermal overload opens and the compressor motor stops, the freon stops flowing and the house gets hot. Once it cools down, it can restart normally upon demand. Thermal protection is sometimes wired in the control circuit meaning it will stop both the fan & compressor but normally it opens the compressor motor leads and leaves the fan running.
This sounds like a problem I just had with mine, and above was the problem. It is basically a switch that prevents the compressor from further damage once it overheats. My ac repairman removed it completely. He said, it is not necessary, just don't turn it off and then immediately back on as the safety net is now removed.
However, the cooling down part takes multiple hours usually not minutes
This post was edited on 5/5/16 at 1:46 pm
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