AboutHoward Livingston Expertise Can answer questions on electrical control circuits, power supply,airflow & distribution, electrical components,refrigerant problems,gas, electric & propane furnaces.No boiler or refrigerator or oil fired furnaces experience.Just HVAC questions please.
Experience 35 years experience in residential & light commercial repair & installation.
Question QUESTION: Hi - have a 10 year old unit that was working fine up to yesterday, when that satisfying sound of the compressor springing to life stopped happening and just the fan turns on outside. Using thermostat turns on outside fan, but no compressor, so controls seem ok. Took cover off case, and proper voltage at all connections to contactor, wiring is intact both low and high voltage - the wire from the capacitor to the contactor is a little toasty on the clip end at the contactor but believed servicable, and the contactor is relatively new (3 yrs). Manually tripping the contactor starts the fan, no compressor. Is there a reset button on these compressors inside the lower part of the case? Only 1 capacitor in wiring box on top side of unit - is that for fan or compressor? Is there a capacitor down on the compressor and could it be causing this if it failed? If so how do you test. So Howard, what's your guess - locked up compressor, freon low or ?? Any homeowner tricks to zero in further?
Thanks in advance.
don
ANSWER: Hi Don, nice to have good info like yours. Need to test the run capacitor for the compressor first.May be a dual for the fan & compressor, maybe not. Then look on the conmpressor for burned wires. If all test OK need to see if it will start when it is cold.Could be a locked rotor but may blow the breaker if so.Could be a stuck rotor from worn bearings & a start capacitor could get it running.Test the caps with an ohm meter set on high. Disconnect wires to test. When terminals are touched the meter will go to high , then drop back to zero. Do these & let me know more if needed.
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QUESTION: Well thanks very much - What a great service - this kind of help is unknown in this day and age. So I would beg your input one more time - I have done more research - as follows. I found a UTube video on how to check whether the compressor is OK electrically or not. Sadly, I opened the cover on my single phase compressor and found the common wire completely burned off and not connected, the start wire just about melted through at the terminal (but maybe caused by heat from the common wire), and the run wire intact. Checking with an ohm meter across the terminals showed infinite resistance (zero on the scale) between common and start, common and run, and start to run. According to the video, the sum of the C-S plus C-R should equal the value of the S-R resistance, which they of course do because they are all zero - but it seems to me this is not a good thing to find. Capacitor is a dual 5/40 MFD 440 volt unit, and i think checks out OK sort of. My digital volt/ohm meter doesn't read MFDs, but the ohm reading does change as you scratch around from common to fan and common to Herm. The meter starts at 1.0 and reads erratically when in contact with the various terminals - maybe not getting a good reading because of corrosion.
My next logical step would be to splice in new connectors for the common and start compressor terminals and give it a try - but am writing to you before I do because I'm guessing it will lock up and trip the breaker and cause a lot of smoke.
Tell me there is hope - please!!
Also - if it is the compressor, would it be better to have someone just come out and replace it, or replace the whole condensing unit. I found a tag saying it was manufactured in February, 1994. The case, contactor and fan appear to be in good condition, so why throw out the whole thing??
But of course, I still have my 1968 Maytag washer and dryer after replacing just about every part in there at one time or another.
Thanks again -
don
Answer Well hello again Don. I have been in this business since 1973 & it has always been fun(well most of the time) because I am helping people. I do this for free for the same reason !
Ok, here we go again. This is a common problem,burned wires. Is there still a metal stud left on the compressor ?? Can you get a wire terminal on the stud. There are special terminals for compressors that will slide on that stud, so hope the stud is still there. I would recommend using the special terminals. They are all metal, the wire crimps on the slides on the stud.
Need to run an ohm test on the compressor from each terminal to a GOOD ground on the compressor, set an analog meter at high ohms. The slighest movement will indicate a ground. Best to use an analog meter.A ground will condemn it. The video test is a good one to, but was your meter set to a lower scale to read a low resistance ?? The CS +CR = SR are pretty low values but is an accurate way to see if the windings are OK. If you can get an OK on these readings(ground & windings) then mess with the wires to try a run test.The capacitor test is hard to interpret with a digital meter, use an analog to see the swing of the needle to test the cap.Get a good contact thru the rust.
Its all ways cheaper to replace the compressor but that depends on the CONDITION of the unit more than the age. Afetr all, there ain't too much in these things for parts ! Right ?? You have 3.5 ton pot & they are selling for about $400 cost for a piston type + lots of markup & labor. A new unit would be about $800 cost +++++++ Move carefully on the tests, you can still have a good pot. Your welcome.
