central a/c compressor not turning on

Question to the cooling gurus here:
The compressor for my central a/c system isn't turning on. The fan inside the compressor housing runs, there is 230V coming out of the contactor and going to the compressor, and there is 24V coming to the contactor from the thermostat.
Is this a symptom of a compressor gone bad, or could it be caused by low freon in the system?
Thanks
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Could be several things. One being burnt wire going to compressor, bad capacitor, compressor locked up. You are best to have someone to look at it. If it's more that 12 years old, you may want to consider getting a new one........
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It's no more than 7-8 years old, the wiring is in good condition. Would low freon in the system prevent this compressor to turn on? Does it have a pressure switch built in?
It's a Lennox Elite Series HS29-036-1P
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How do you know the wiring is good? Did you "open up" the compressor to see if all the wires were secure on the terminals? Seen many a wire that was "burned" off the terminal (mostly due to loose connection) and that will keep the compressor from coming on.
Yes, most models have a high and low pressure "limit" that will keep the compressor from coming on if the refrigerant level gets too high or low. Sometimes those limit switches can go bad, too (with the same results). If the capacitor is bad, it will do the same thing.. Most have dual capacitors and if it's bad, either the fan or compressor or neither will come on.
Ask your friends or neighbors who they would call if they had a problem with their unit. Call them early in the day and have them come out during regular business hours and the bill will be less painful.....
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Yes, I opened the housing and checked all terminals. No corrosion or loose wires. Unless you meant the motor winding was burnt - that I couldn't check obviously.
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I doubt t here is a pressure switch -- perhaps a high pressure cutoff. Since there is 220 VAC to the compressor, that's aparently not a concern. A pressure switch would more likely prevent the AC to the compressor.
What's the amperage? I'm thinking either locked compressor (entire compressor needs replacing) or bad run capacitor.
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I didn't measure the amperage. It's running now (cooled off in the evening), so it's not locked up.
What's the prodcedure for checking the capacitor?
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Switch off power, and then remove the cap. Use a VOm that has a scale for farads.
Since it seems to over heat, perhaps your system isn't releasing heat as efficiently as possible.
Heating up and dying is one of the variations of "locked up".
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Disconnect power. Disconnect wires from compressor. Test with VOM on "ohms" setting. A HVAC tech can check this.
Sounds like you're about at the limit of your training. How abotu call a HVAC repairman?
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actually, no
a capacitor with high leakage may check good this way and still be bad just replace the capacitor, it is easy, the capacitor is likely worn out, and they only cost about $8 at Johnstone bring the old one with you to match up, and make a drawing of what wires went where, colors, etc. before removing old one.
PS - a capacitor can shock the hell out of you, short terminals with a screwdriver after removal, and wear latex gloves during removal

no, "locked up" is locked up! a locked compressor won't be running ever again unless it is rebuilt
I vote that the capacitor is the likely culprit
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You dont have a vom with a scale reading in Farads, and doubtfull youve ever seen a cap as large as 1 farad.
Set to midrange ohms and watch for needle swing....after initial charge-up it will swing twice as far on reversal of the leads until you discharge the cap.

SVL
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I had a dog once........
;-]
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Stormin Mormon wrote:

So is being a 'devout' follower of brother Brigham Young.
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Don't think Brigham Young has any followers. At least I've not met any. Actually, I don't know anyone who worships Brigham, or the previous prophet, Joseph Smith Jun. Since you bring up the subject.
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Stormin Mormon wrote:

I said nothing about 'worship'? You did.
You're as blind as ole Brigy hisself. Smith was a con.
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Update after the service technicians checked out the system:
They measured the refrigerant pressures, voltage, amperage, temperature spread for ambient and cooled air - and couldn't determine anything wrong with the system. Then they asked if there were any powere failures or surges?
Yes, there was a surge before I noticed the a/c wasn't cooling, and apparently that caused the compressor thermal protection switch to open. As I mentioned earlier, the a/c ran fine last night - after being shut off for couple of hours. The compressor cooled off, the switch closed, and all is well again.
Thanks to all who responded.
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Hi reader, hope you are having a nice day
On 12-Jun-05 At About 18:06:27, reader wrote to All Subject: central a/c compressor not turning on
r> Question to the cooling gurus here:
r> The compressor for my central a/c system isn't turning on. The fan r> inside the compressor housing runs, there is 230V coming out of the r> contactor and going to the compressor, and there is 24V coming to the r> contactor from the thermostat.
r> Is this a symptom of a compressor gone bad, or could it be caused by r> low freon in the system?
It could be a bad compressor but it needs to be checked to verify this. you should call a local company to verify everything
-=> HvacTech2 <=-
.. "A friend of mine is in jail for counterfeiting pennies..."- s.w.
___ TagDude 0.92+[DM] +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ spam protection measure, Please remove the 33 to send e-mail
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Lennox HS29-036 is a 3-ton, 11 to 12 SEER AC. It could be a wire burnt off the compressor or a bad capacitor, If the compressor shell is hot, most likely the compressor overheated and the internal overload is open. If the compressor overheated, could be a stuck compressor, bad capacitor or low Freon (Freon cools the compressor motor). It could also be bad windings. Charging a system is beyond most homeowners, requires EPA certification to do it legally.
Stretch
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Here's an update:
I left the system off for a couple of hours, and turned it back on this evening. It's running now and cooling.
So, I would guess the heat during the day (over 90 deg F.) and low freon caused the compressor to overheat, and the overload switch opened. Do you guys agree?
I'll have it serviced tomorrow and checked for the leak location.
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