capacitor

[54regcab]

Another handy tool is an ESR tester. It sends a high frequency signal through the capcitor and measures internal AC resistance. Test can be done in circuit, no disconnecting required. Since the signal is high frequency very little passes through the motor windings. As capacitors dry out thier ESR increases. As ESR goes up capacitors run hotter. Eventually the capacitor overheats an the top bubbles up.

http://en.wikipedia.org/wiki/ESR_meter

[timebuilder]

There is a low price kit for "blue ESR capacitor tester meter" on eBay.

I believe this is the same technology used in battery conductance testers, which gives a better picture of battery condition than a simple load test.

[54regcab]

There is a low price kit for "blue ESR capacitor tester meter" on eBay.

I believe this is the same technology used in battery conductance testers, which gives a better picture of battery condition than a simple load test.

The ebay kit is the one I have if it's the one I think you are talking about. Translucent plastic.

[timebuilder]

How do you like it?

[54regcab]

Works well, but I would choose removable leads if I was to design one of my own. The only caps it has a problem detecting bad are those that break down under load.