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-   -   Sometimes my cenral AC run and sometimes not running (http://www.diychatroom.com/f17/sometimes-my-cenral-ac-run-sometimes-not-running-185204/)

tuanngnt 08-13-2013 01:38 AM

Sometimes my cenral AC run and sometimes not running
 
Hi,

I need some help on my central AC compressor. I notice that sometimes it runs and sometimes it did not run. When it did not run, I went to my house Main Switch Panel and I reset it by turn the switch Off and ON; then the compressor worked again. I noticed that whenever I adjust the temperator from the thermostat or turn AC on and off on the thermostat, the compressor has a problem to start to run. Is this related to capacitor problem? Please help.

ON the title, I mean the compressor sometimes run and sometimes not running; but the fan still working. Is the capacitor is bad?

tuanngnt 08-13-2013 04:05 AM

What I find out is the compressor stop running.

tuanngnt 08-13-2013 06:11 AM

I changed the capacitor; but no good at all.

biggles 08-13-2013 07:42 AM

that turning on an off real quick could be one problem...he pressures need to equalize for a restart so always shut the stat off when resetting and then work he stat after couple of minutes.if the condenser fan is running but not the compressor could be a internal safety cause the main contactor is in running the fan outside..internal heat overload...

gregzoll 08-13-2013 07:55 AM

There is not a timer somewhere inside the cabinet, or furnace, which could be failing. That would be the first thing I would be looking for, along with a bad contactor on the outside unit, that is failing.

tuanngnt 08-13-2013 07:55 AM

Quote:

Originally Posted by biggles (Post 1228677)
that turning on an off real quick could be one problem...he pressures need to equalize for a restart so always shut the stat off when resetting and then work he stat after couple of minutes.if the condenser fan is running but not the compressor could be a internal safety cause the main contactor is in running the fan outside..internal heat overload...


Hi,

Please help me out. Here is what I found out more: When I turn on the AC on the thermostat, the thermostat indicated cool and I went outside to see the compressor and fan both running. I went inside and feel the cool air. This whole process run about 10 minutes; then suddenly the thermostat indicated every thing stop; then on the outside, the compressor and fan stop running too. The stopping period last about 5 minutes; then the thermostat indicated running again. I went outside and see the fan running but NOT the compressor; I hear the repeated noise from compressor trying to start. I went inside and notice that NO cool air at all. What is going on? Please let me know.

yuri 08-13-2013 08:00 AM

your thermostat is faulty and short cycling. the compressor needs to be off for 5-10 minutes for the Freon pressures to equalize. if they don't then the compressor stalls and cannot start against the high pressure. long story short go to Home Depot and buy a Honeywell Focus Pro thermostat and it will have a 5-10 minute built in time delay ( read the programming and activate it) which should keep the compressor off long enough and it should not recycle/start itself that often either. make sure there is no heat source near the thermostat causing it to restart itself like bright Sunlight or TV or other heat producing items.

gregzoll 08-13-2013 08:01 AM

Pull the thermostat and tie the Y1 & R wires together, to see if it continues to run. If it does, then bad thermostat.

yuri 08-13-2013 08:05 AM

y1 and C will blow the transformer or fuse or board plus you need a G circuit.

tuanngnt 08-13-2013 08:06 AM

Quote:

Originally Posted by gregzoll (Post 1228691)
Pull the thermostat and tie the Y1 & C wires together, to see if it continues to run. If it does, then bad thermostat.

Ok, I will do that. By the way, I noticed that after the compressor could not run any more, I leave the system off for about few hours; then turn the AC on again from the thermostat; then the compressor run again and cool air come out again; but it will stop running for about 10 minutes; so the whole process start to happen again.

It sounded to me the compressor is overheat or something. I wish not because I am unemployed right now. If it is thermostat, then I happy for it.

tuanngnt 08-13-2013 08:09 AM

Quote:

Originally Posted by yuri (Post 1228693)
y1 and C will blow the transformer or fuse or board plus you need a G circuit.

So don't wire this right?

yuri 08-13-2013 08:10 AM

if you tie those wires together damage will occur. would need to use R to Y but that still is incorrect as the furnace fan won't run on some units. he is trying to be helpful but yes that is wrong. replace the thermostat, costs under $75. don't buy any other cheaper ones as they are mostly Chineez offshore poor quality.

tuanngnt 08-13-2013 08:15 AM

Quote:

Originally Posted by yuri (Post 1228697)
if you tie those wires together damage will occur. would need to use R to Y but that still is incorrect as the furnace fan won't run on some units.

My house is split system AC unit and I noticed this happening downstair. I also went up upstair to use other thermostat to turn on the AC and still did not see the compressor running at all; so no cold air coming out. If I wait for a few hours; then I noticed that I can start the system with compressor running again for about 10 minutes.

I still have a spare Honeywell thermostat that I knew it is working. I will give it a try on that thermostat.

Is this really thermostat? If it is, then why my upstair thermostat did the samething...that mean when I turn the AC from that thermostat, the compressor did not run at all; so no cold air at all; but the compressor fan is still running and blower fan is running.

yuri 08-13-2013 08:21 AM

you may have a larger problem like low voltage to the units or your house. both units should not have the same problem. that is VERY hard on the compressors and can damage them. may want to get a Pro to check them. you would need to check the voltage to them AND while it is trying to start. could be the compressor(s) are getting old (if they are old units) and seizing up and may need a hard start kit or you got other problems like a bad thermostatic expansion valve, burned contacts in the contactor, or damaged wiring at the compressor etc. sounds like a voltage problem too me. best to get a Pro to check them before some very expensive damage occurs.

tuanngnt 08-13-2013 08:27 AM

Quote:

Originally Posted by yuri (Post 1228700)
you may have a larger problem like low voltage to the units or your house. both units should not have the same problem. that is VERY hard on the compressors and can damage them. may want to get a Pro to check them or electrician. you would need to check the voltage to them AND while it is trying to start. could be the compressor is getting old and seizing up and may need a hard start kit or you got other problems like a bad thermostatic expansion valve. sounds like a voltage problem too me.

This compressor is 9 years old. Last year I changed the evaporator coil; then
my system is running well since September 2012. I have used it with the new evaporator coil for many months; then Kaboom I noticed the problem happening yesterday.


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