Failed air conditioner run capacitor

DANGER: If you make a mistake while working on your air conditioner, you will die. DANGER: Hazardous voltage. Contact will cause electric shock, burn, or death. Most household air conditioner circuits can deliver over 40 amperes at 240 volts AC. DISCLAIMER These photos and descriptions are provided for information only. Do not attempt. This Web page is NOT created by, sponsored by, endorsed by, affiliated with, or otherwise connected to Trane Inc., Ingersoll-Rand Inc., General Electric Inc., Genteq, or Regal-Beloit Inc. The creator of this Web page, other than owning a Trane air conditioner, has NO CONNECTION with Trane Inc., Ingersoll-Rand Inc., General Electric Inc., Genteq, or Regal-Beloit Inc. The run capacitor shown here is for one specific model of Trane air conditioner. The parts for other models and makes will vary.

Note: If linking from another site, please don't link directly to the photos below. Link to this page with descriptions and disclaimer. The URL for this page is http://www.birdbird.org/electronics/run-cap/ac-run-cap.html.

The photos I took were shot with a Nikon Coolpix L20 digital camera. They have been reduced from the original dimensions. The thumbnails are 11 KB to 14 KB and the large photos are 175 KB to 250 KB.

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The house I used to live in had a Trane XE 1000 air conditioner. It was installed in about 1995, before I bought the house, and was probably 2.5 or 3 tons. When it was about 10 years old, it failed to turn on one day; the compressor sounded like it wanted to start, but the condenser fan wouldn't start at all. I traced the problem to a bad run capacitor. I bought a replacement from a local appliance parts store and it fixed the problem; the air conditioner continued to run fine for the approximately 4 years I still lived in that house.

While cleaning up recently, I found the original bad run capacitor, and figured I would put up a few pictures of it before throwing it away.

This is what a good capacitor should look like; this image is from the Genteq capacitor catalog. (Genteq bought GE's capacitor business.) Note how the lid of the capacitor sits below the top rim of the capacitor.

This illustration from the Genteq catalog shows what the capacitor is designed to do if there is a fault in the capacitor that raises the internal pressure. The top bows out and cuts off the connection between the terminals and the rest of the capacitor, stopping the current flow. I am pretty sure this is what happened to mine; the top is bowed out in the pictures below, and it measures open circuit between any pair of terminals and any terminal and the case.

	General view of the failed capacitor. It is rated 7.5 uF and 45 uF at 440 V AC.
	Closeup of the top part of the failed capacitor. Note how it is bowed upwards.
	Looking down at the top of the failed capacitor.