How to Replace Starter Capacitor on AC Condenser

Here’s a short video mostly to let you hear what it sounds like when the capacitor is bad (and not when the relay is bad):

Another common problem is when your condenser unit’s relay goes bad and that is a different issue.  Before you tear into your condenser unit to replace the capacitor you want to cut the power to your condenser.  First of all I can’t accept any responsibility for anything irresponsible you do so make sure you know what you are doing and are comfortable with working around electricity before you go any further.  Follow the flexible conduit from the condenser unit to your building and look for the metal box it runs into:

Inside there should be a shut-off switch or a paddle you can pull out.  In my case there is a paddle:

You can pull that handle (circled in red) and the paddle will come straight out, disconnecting the power from the condenser.  One thing to note: you can flip the paddle over and then reinsert it and it will be off.  Don’t forget to pay attention to the orientation of it when trying to turn it back on because you can insert it and it still be off (for use when you want to shut it off for the winter but don’t want to take the paddle with you).

Now you can take off the panel that covers the area where we need to get to.  This will be easily found by following all the wires to the condenser.  I circled the bolts you’ll need to remove.  Take these out and then slide the panel straight down to remove it.

I forgot to take a picture of the overview of the parts inside (and I’m doing this tutorial in retrospect).  There’s not that much inside so you’ll be able to recognize the parts from my pictures.  Another common thing that goes bad on these condenser units is that the relay goes bad.  The relay is the switch that physically connects the power to the condenser unit.  If you watched the video and you are experiencing something similar then I’m going to assume that your issue is the capacitor and not the relay.  This is what the relay looks like though:

The part we are going to replace is the capacitor and it looks like a silver pop can clamped to the side of the condenser unit with a metal band.  Make sure not to short the leads of the capacitor.  If it’s bad it won’t have a charge but you don’t want to mess with large capacitors.  You could end up with a molten fireball if you shorted a fully-charged capacitor.

The starting capacitor

Now one thing you’ll definitely want to do is take a picture of your capacitor with the wiring in place so you know how to put it back together because I’m not going to go over those details.  That’s actually why I took this picture.  I also scratched into the capacitor’s can the colors of the wires so I could compare when I get the replacement and would know how to hook it back up.

Now it may not be possible to tell for sure whether this capacitor is bad based on looks but when these capacitors fail many times they will bulge up on the top.  You can see that my capacitor is bulging (verses inset like a pop can’s bottom). If you take it to a HVAC parts store they can test it for you and let you know whether it is bad too.  If you are in the Chicago area a good place to go is Sundberg Company Appliance Parts and that’s where I got my replacement.  If you don’t mind waiting for delivery (or maybe it’s going to be cool for the next few days) you can get them on amazon.com too for real cheap.

Back to the repair.  Once you’ve taken good notes as to how things are connected, pull off the connectors and then loosen the screws holding the band tight to the frame of the condenser.  Slip in your new capacitor and reconnect the wires, tighten the band screws, replace the panel and screw it back on, and then turn your power back on by reinserting the paddle in the disconnect box (pay attention that the right side of the paddle is up to turn it on) and then you can go inside and cool off. You just probably saved yourself over $150 in repair costs for not much work.

Other thoughts:

• I’ve heard of situations where the furnace and/or the air conditioner will not come on simply because the battery in the thermostat had run low enough that it didn’t have the juice to switch the relay in the furnace.  That’s something else to check out (and real simple at that).
• The relay is another common thing that goes bad on these condenser units.  Mine hasn’t gone bad but when it does I’ll document it on this blog.