Air Conditioner cycles off after 3 to 5 minutes---need troubleshooting help

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I have a 20-year old Frigidaire through the wall air conditioner.
When first turned on it does a great cooling job. A digital thermometer right at the outlet is showing 40F.
After three to five minutes, the compressor turns off and the cooling stops.
After maybe 5 minutes the compressor comes back on and cools for another 3 to 5 minutes.
I took the unit outdoors and cleaned the fins with a garden hose and a fin-cleaning aerosol spray. It is difficult to view the fins visually, but I'm fairly sure they are clean. The cleaning did not seem to change the cycling time at all.
I'm in a small town and it is a heat wave. It is difficult to get a repair person in the best of times---and I'd rather save the money and repair it myself if it is something I can handle.
How do I troubleshoot from this point?
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I have a 20-year old Frigidaire through the wall air conditioner.
When first turned on it does a great cooling job. A digital thermometer right at the outlet is showing 40F.
After three to five minutes, the compressor turns off and the cooling stops.
After maybe 5 minutes the compressor comes back on and cools for another 3 to 5 minutes.
I took the unit outdoors and cleaned the fins with a garden hose and a fin-cleaning aerosol spray. It is difficult to view the fins visually, but I'm fairly sure they are clean. The cleaning did not seem to change the cycling time at all.
I'm in a small town and it is a heat wave. It is difficult to get a repair person in the best of times---and I'd rather save the money and repair it myself if it is something I can handle.
How do I troubleshoot from this point?
+++++++++++++++++++++++++++++++
I'd call a HVAC company and get on the waiting list. This heat wave is brutal.
20 years old?
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I have a 20-year old Frigidaire through the wall air conditioner.
When first turned on it does a great cooling job. A digital thermometer right at the outlet is showing 40F.
After three to five minutes, the compressor turns off and the cooling stops.
After maybe 5 minutes the compressor comes back on and cools for another 3 to 5 minutes.
I took the unit outdoors and cleaned the fins with a garden hose and a fin-cleaning aerosol spray. It is difficult to view the fins visually, but I'm fairly sure they are clean. The cleaning did not seem to change the cycling time at all.
I'm in a small town and it is a heat wave. It is difficult to get a repair person in the best of times---and I'd rather save the money and repair it myself if it is something I can handle.
How do I troubleshoot from this point?
************************************************
At 20 years, I'd be out looking at new, more efficient units that are the same size or smaller to fit in that hole.
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I'd do the fin cleaning routine, again. That's my best diagnosis, from here.
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Bad thermostat ( short cycling) Low on refrigerant (cycling on a low pressure switch) Dirty or bad condenser motor (cycling on a high pressure switch)
All 3 are easy to troubleshoot if you have any knowledge of basic electricity. Just find the appropriate terminals and wire the control out.
In this heat wave and your 3 to 5 minute cycle I am betting on the thermostat.

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scribbled

out.
Obviously he doesn't know any of that stuff....so, I myself would chuck the old POS in the trash (SEER 4 maybe?) and go to Conns, Fry's or similar and buy myself a brand new one, with remote controls with SEER rating in the 13s for around $230.
HTH
bill
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Bob wrote:

Sometimes the overload relay on the compressor will become overly sensitive due to corrosion and or erosion of the contacts which will create a resistance which in turn will create heat which will case the overload relay to click open. When the AC starts and stops, do you hear a "click"? If so, that would be the overload on the compressor. It should be easy to replace. You have to check the supply voltage because that's another thing that, if low, can trip the overload.
TDD
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Bob wrote:

I'm with Ed. You should be able to get a new unit that will pay for itself fairly quickly in energy savings compared to a 20 year old unit.
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Youve done all you can as a homeowner . Its time to call for a professional diagnosis..but i wouldnt dump alot of money into it. 20 years is over the average life expectancy...and especially if you live in a southern state.
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Tomorrow is my day to work on this again.
As to the 20 years.....this unit has actually been used very little, and has been well protected during the off season.
Here's why I'm reluctant to just dump this air conditioner and buy something else (aside from being short on cash): when the air conditioner is turned on, it is quiet and smooth and cools the output air to 40 F immediately. To me that seems like all the internal parts are doing their jobs well and something external (like a control or heat exchanger) is causing the cycling. If it is low on refrigerant would it cool to 40 so quickly? Same with dirty or bad condenser motor?
I could see the thermostat being the problem or the fins are still not clean enough.
Is my logic correct? Is getting to 40 quickly really telling me that certain parts are OK?
Incidently, the parts drawings for this unit are still on the web at: http://www.partselect.com/AdvancedModelSearch.aspx?ModelNum=AK16E6RRBA&mfgModelNum=&fkMfgID=4
It was 102 here today and forecast hotter tomorrow.
B.
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Looking at the wiring parts list that you provided, i see no mention of hi or low pressure refrigerant cutoffs. If the motor continues to run and it is the compressor kicking off, the problem is going to be the thermostat or as pointed out by another user, an external overload under the compressor cap. If the entire unit is kicking out, that is, the fan and the compressor, you could have a faulty thermostat or selector switch. Without being there, this is the best I can do for you. 40 seems a bit cool but is possible. You stated that you removed the unit and cleaned the coils. I assume you cleaned both the evaporator and condenser coils. Also make sure the filter is clean. As stated in my previous post, my bet is on the thermostat.
Tomorrow is my day to work on this again.
As to the 20 years.....this unit has actually been used very little, and has been well protected during the off season.
Here's why I'm reluctant to just dump this air conditioner and buy something else (aside from being short on cash): when the air conditioner is turned on, it is quiet and smooth and cools the output air to 40 F immediately. To me that seems like all the internal parts are doing their jobs well and something external (like a control or heat exchanger) is causing the cycling. If it is low on refrigerant would it cool to 40 so quickly? Same with dirty or bad condenser motor?
I could see the thermostat being the problem or the fins are still not clean enough.
Is my logic correct? Is getting to 40 quickly really telling me that certain parts are OK?
Incidently, the parts drawings for this unit are still on the web at: http://www.partselect.com/AdvancedModelSearch.aspx?ModelNum=AK16E6RRBA&mfgModelNum=&fkMfgID=4
It was 102 here today and forecast hotter tomorrow.
B.
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......and here's what I found today........
I by-passed the thermostat and the cycling seems to have stopped.
I did look at the coils again, both by checking airflow and shining a flashlight through the fins, and I'm pretty sure the coils are plenty clean.
Next challenge:
I looked at Frigidare replacement parts and the thermostat is in the $110 range----ouch!!!!! The Frigidare part # is G158995.
Looking further on-line I found a universal replacement thermostat for about $35 at http://www.appliancepartsworldwide.com/Store_Part.aspx?Id=1018989
Does anyone have any comments on using a universal part to save some cash?
My air conditioner is 220 volt. Looking at the wiring diagram it looks like the control circuits are also 220 volts, In the various online parts catalogs I don't see any callouts for voltages for thermostats. Am I missing something here?
B
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Not only is the voltage important, so is the amp rating. The specs for the part you propose are: Universal type window unit thermostat kit.
Range: Cold Off (52F) Warm On (93F) Diff: 6F Capillary: 18" End 1" Aircoil SPST, F.L.A. 20A, L.R.A. 80A
I would go for it

--------------------**********************-------------------------------------------------------------------------------------
......and here's what I found today........
I by-passed the thermostat and the cycling seems to have stopped.
I did look at the coils again, both by checking airflow and shining a flashlight through the fins, and I'm pretty sure the coils are plenty clean.
Next challenge:
I looked at Frigidare replacement parts and the thermostat is in the $110 range----ouch!!!!! The Frigidare part # is G158995.
Looking further on-line I found a universal replacement thermostat for about $35 at http://www.appliancepartsworldwide.com/Store_Part.aspx?Id 18989
Does anyone have any comments on using a universal part to save some cash?
My air conditioner is 220 volt. Looking at the wiring diagram it looks like the control circuits are also 220 volts, In the various online parts catalogs I don't see any callouts for voltages for thermostats. Am I missing something here?
B
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Hey Big Bob (from Bob);
I love the education I'm getting. Where did you come up with the specs for the Universal type window unit thermostat kit?
SPST= single pole, single throw. What is F.L.A. and L.R.A.?
Is it Universal enough that the mounting holes are going to match, or is that too much to ask?
Stormin Mormon: The tube spacing looks OK, but before I spend buy any new parts, I am going to try moving the tube somewhat and see what happens.
Bob
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SPST= single pole, single throw. What is F.L.A. CY: Full Load Amps
and L.R.A.? CY: Locked Rotor Amps.
Stormin Mormon: The tube spacing looks OK, but before I spend buy any new parts, I am going to try moving the tube somewhat and see what happens.
CY: Sounds like a plan. No sense in replacing a good part.
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On Jun 29, 4:26am, "Stormin Mormon"

I didn't realize I was going to learn so much from this repair task.
I put locked rotor amps in Google and found this response on a forum: (Now I wonder how electric motors in space dissipate heat---like on the Intl. Space Station where I assume electric motors position antennas and solar panels).
Re: locked rotor amps (LRA)
--------------------------------------------------------------------------------
Just a note on electric motors If a motor is running completely unloaded it will turn at nearly synchronous speed. This speed depends upon the way in which the motor is constructed. A two pole motor running with a supply frequency of 60 hz would in theory turn at 3600 rpm. And a 4 pole motor would run at 1800 rpm. A 50 hz supply would reduce these speeds in proportion to the supply frequency. In these hypothetical conditions the motor would absorb no current from the supply. However as we dont yet live in a perfect world, the motor is not 100% efficient. The windings have resistance, the bearings have friction and there are windage losses due to the rotor velocity. These inefficiencies tend to slow the motor slightly. As this happens power is taken from the supply to overcome these losses until the motor speed stabilises at what is termed is free running speed. As energy is a constant this power is ultimately converted in to heat which in this free running state is dispersed into the atmosphere. For this to happen there must be a temperature difference and therefore the internals of the motor heat up to a temperature at which this heat can be conducted from the motor.
An increasing load applied to the output shaft of the motor results in further slowing of the motor, more current is absorbed to overcome the applied load plus the increased internal inefficiencies of the motor which result in higher internal temperatures. This effect will continue until the load is sufficient to stall the output shaft. The current drawn from the supply at this condition is termed the motor Locked rotor amps.
However our compressor motors are not designed to operate at this stalled condition. We require them to turn our compressors at a speed to meet with our cooling requirements. Motors are therefore usually designed to operate with a slip of approx. 4 % of full load speed. (Slip is the percentage of synchronous speed the motor is running at). This condition is termed the Full load speed and the Rated full load power of the motor. The power absorbed at this condition is termed the Full load amps or fla This is usually in the region of one sixth of the locked rotor amps. The motor being designed to dissipate the internal heat at this condition without causing damage to the insulation of the motor windings. Allowance being made for short time overload and for starting.
Remember its the temperature limitations of the motor windings that determine the maximum power of the motor. Thats why we fit klixons and other temperature sensors as the fuses wont necessarily protect against overload
So if you switch on a motor direct on line (DOL) it will initially take up to 6 / 7 times the flc of the motor as this is in effect a stalled condition, admittedly normally for only for a very short time.
This starting current in most applications can be reduced by various means depending upon the torque / speed characteristics of the compressor or whatever the motor is connected to.
Some small motors are designed to operate at a stalled condition indefinitely, think of car door window winder motors and some control motors.
Hope this helps
[The site is: http://www.refrigeration-engineer.com/forums/showthread.php?t=4695 ]
I don't follow the reference to car window motors. Isn't the power removed at the end of travel?
A little later today I'm going to stop worrying about car windows and the space station.
I will remove the jumper wire I placed on the air conditioner thermostat and reposition the sensor tube. The rubber block appears to be in its proper place, but maybe repositioning will stop the cycling. If it doesn't, I will order the Universal replacement thermostat.
Bob
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Bob wrote:

Did you install a jumper wire in place of the thermostat? If the AC ran OK with the jumper in place, then it's the thermostat. The way thermostats are mounted on window AC units is important because it also detects icing of the evaporator and shuts off the compressor. The rubber or foam block that the sensing bulb is mounted on is necessary for proper operation.
TDD
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Sorry it took so long to get back to you. Sounds like Stormin answered a few of your questions. What I did was go to the item you provided a link for and then put that part number in Google followed by the work specs. A page from another site popped up with the specs. As far as the mounting holes, well in the past when I used universal replacements, at times I had to drill a new hole or 2 in the faceplate to get it to mount. I would rather drill a few holes than spend and extra 70 bucks for an OEM stat.
wrote:

Hey Big Bob (from Bob);
I love the education I'm getting. Where did you come up with the specs for the Universal type window unit thermostat kit?
SPST= single pole, single throw. What is F.L.A. and L.R.A.?
Is it Universal enough that the mounting holes are going to match, or is that too much to ask?
Stormin Mormon: The tube spacing looks OK, but before I spend buy any new parts, I am going to try moving the tube somewhat and see what happens.
Bob
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I removed the jumper from the thermostat and repositioned the tube at some distance from the cold coils and fins.
The air condiioner ran about three minutes and cycled off. I guess I've pretty well proven that the thermostat is bad.
I just ordered the universal replacement by phoning the 800 number in the website I mentioned several posts back. They said they'd get it out yet today by UPS ground. I ought to see it by Thursday or Friday. (Is Friday, July 3, a UPS holiday?)
With any luck my next posting on this site will say I didn't have to drill any holes and everything is fixed.
Meanwhile, thanks to everyone here for all the help. Assuming that this fixes the problem, I'm glad I didn't try to get some one to make a service call, or, worse yet, toss my unit in the dump and buy a new one.
Bob

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I sense, strongly, that you're going to fix it.
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