Think this AC capacitor is bad? - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: June 22, 2016, 10:44:27 am
content: Hey all, so my AC was cold as sin up until two days ago, where it wasn't working at all, I checked and the thing starting up, which used to draw 18 amps briefly, draws 30, then gives up turning on the compressor and drops back to 1.7 - 2 amps for the main fan.The compressor was extremely hot too, it was probably doing this for at least 20 hours though.I have it a try with a smaller electrolytic cap rated at 150 microfarad but that blew it's vent (I wish I had been recording it was great), so clearly electrolytics aren't up to the task. The original measures 60 microfarad (on the tin and my meter, but I don't have an esr tester), but the spot where the vent is looks like it might be bulged, I don't know, it's extremely uniform and ungiving, so maybe that's what it normally looks like? I can't tell, so figured maybe someone here can chime in.The compressor did usually draw around the 18 amp range while starting but then dropped to 8 amps total, but it never had trouble starting except for when I had it on a power bar with a breaker, and it's so sudden I don't know if the motor would just get that stiff out of nowhere.I just don't know if the capacitor going bad would cause that massive draw, I suppose it could even though it's only a 60 microfarad cap. I would be so happy if this was the cause, it should be relatively cheap, and while I did get this free last year due to a leak problem I fixed, there are no other free ones locally, our windows only work with the stand up hose vent ac units, and all of those on kijiji are minimum 200 which I just can't afford at all, plus this place has radiators, so there's almost no air circulation.

author: Photon939
author_rank: Regular Contributor
timestamp: June 22, 2016, 01:12:19 pm
content: The capacitor is a usual failure point but it's strange that it still reads 60uF on your meter. Usually when they die they won't report normal capacitance values. Since run capacitors aren't electrolytic they don't usually have ESR problems. The high amp draw you are seeing is the LRA of the compressor motor (locked rotor amps)I would try another capacitor first but it's also possible the compressor may be seized. Does the AC unit have a start capacitor, PTC or relay? They may be hidden inside the compressor terminal cover.

author: SeanB
author_rank: Super Contributor
timestamp: June 22, 2016, 06:41:48 pm
content: Hot compressor, capacitor reads 60uF so what you have is a snapped motor shaft, which is locking the rotor and tripping the internal overload relay. If the capacitor was failed it would measure under 40uF ( around what will stop it starting when hot) and as it is not you have a failed compressor.Depending on the AC type you can either have the compressor replaced, or you need a new one. Repairable with the right equipment, but not something you can DIY without. You need a decent acetylene torch to unsolder the suction line and HP port, and need to recover the charge first before removal. Afterwards you need to at a minimum flush the system, and then pressure test the repaired unit for a few hours then pump down to a vacuum for a while to get residual moisture out. Then recharge with the correct mass of refrigerant.

author: XOIIO
author_rank: Super Contributor
timestamp: June 22, 2016, 07:18:43 pm
content: Quote from: SeanB on June 22, 2016, 06:41:48 pmWell, I'm likely never going to find a compressor that would fit in this, or if I could it would be expensive, which is the same issue as getting a new one, I'm completely broke.Of course it had to happen right in the middle of summer in this crappy stuffy place. Guess I'm going to spend the next couple months constantly feeling way too hot and/or sweating, because even with a good fan (using a 12v one from a server power supply that's fairly beefy but only helps if it's aimed right at my face) there's no real cool air to circulate around.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 22, 2016, 11:06:35 pm
content: Try a hard start kit. They're cheap so worth a try.

author: SeanB
author_rank: Super Contributor
timestamp: June 23, 2016, 07:39:56 pm
content: He did try a 160uF electrolytic, which is basically a hard start kit without the PTC, and it did not move. When cold disconnect the power and get to the compressor, and remove the plastic cover on the terminals ( normally held on with either a small metal clip or a small nut on top) and check the spade terminals are still nice and firm, and not burnt where they go on the terminals of the compressor. If they are fine then shot compressor, but if they are burnt it might be fixable with a new spade connector on the cable.

author: XOIIO
author_rank: Super Contributor
timestamp: June 23, 2016, 08:36:06 pm
content: Quote from: SeanB on June 23, 2016, 07:39:56 pmThe compressor does try to start, but it just doesn't keep going, it's like it can't get enough juice. I'll check the connections on the compressor side.

author: SeanB
author_rank: Super Contributor
timestamp: June 25, 2016, 07:15:04 am
content: It goes buzz then stops is not starting, but tripping on internal overload.