Re: Why is it so hard to test a Condenser? (Was: Condensers for Johnson / OMC)

[vintin]

quote jnjvan:

If you really want to thoroughly test a condenser, you need to apply real world conditions. These include the voltage and current that they see in service, as well as heat and vibration. Merc-O Tronic testers, Stevens testers, and the old magic eye testers all are capable of testing at the correct voltages and (possibly) currents. The problem with bench testers is that they don’t include the heat and vibration part. I believe that heat is a primary contributor to parts like condensers and coils that test OK on the bench, and in a quick run in the barrel, but fail three miles from the launch ramp.

I work as an electrical engineer, designing electronic controls for commercial vehicles (i.e. trucks). The primary enemies of electronic components in harsh environments are heat, vibration, humidity, and deterioration due to aging. All of these are present in old outboards.

John Van

Hi John,

Once the condenser fails under real life conditions, are you suggesting that it may still test good on a bench tester?

My understanding is that once the dielectric is compromised, the cap is bad from then on and a bench tester would pick it up.

I don’t have a capacitor checker but I often test them for short or open with a volt meter and watch the resistance rise as they charge up, usually going to the infinite.

Any advice about bringing an old capacitor that has been sitting idle for decades back to spec by applying a very slowly increasing voltage giving the cap time to ‘reform’? I know it’s a technique used on long idled audio equipment and wonder how it might apply to the condensers we find in our old outboard motors. I’ve never found an open or shorted ignition cap in my limited experience with old outboard motors.

Thanks,

Dan