Coil Capacitor Testing - Tech Tip
Posted: Sat Jul 31, 2021 1:55 am
Capacitor testing with the ECCT sometime produces a confusing result:
The correct capacitor Value is displayed BUT the Poor LED is illuminated?
So is the capacitor good or does it need to be replaced?
The capacitor is Good and does Not need to be replaced. Here's why.
Good capacitors have very low leakage current which translates to High Leakage Resistance, typically greater than 50,000,000 Ohms. So the Leakage Resistance test threshold was set much lower, to 5,000,000 Ohms
Many old coils may have degraded wire insulation, slightly conductive potting and/or conductive black paint on top of the coil which can cause higher leakage current that translates to Lower Leakage Resistance that is below the 5,000,000 Ohm Leakage Resistance test limit causing the Poor LED to be illuminated. That’s unfortunate because Leakage Current does not significantly affect coil performance unless it is very severe, well less than 1,000,000 Ohms. In hindsight, the capacitor Leakage Resistance test limit should have been set much lower to avoid confusion.
The bottom line is: Judge capacitors based on their Value, not Leakage Resistance. If the Capacitor Value tests greater than 0.33uF and less than 0.68uF it need not be replaced.
This capacitor is Good and does Not need to be replaced even though the Leakage Resistance Fails the 5,000,000 test limit.
The correct capacitor Value is displayed BUT the Poor LED is illuminated?
So is the capacitor good or does it need to be replaced?
- Cap Test Poor Leakage.JPG (37.51 KiB) Viewed 2268 times
Good capacitors have very low leakage current which translates to High Leakage Resistance, typically greater than 50,000,000 Ohms. So the Leakage Resistance test threshold was set much lower, to 5,000,000 Ohms
Many old coils may have degraded wire insulation, slightly conductive potting and/or conductive black paint on top of the coil which can cause higher leakage current that translates to Lower Leakage Resistance that is below the 5,000,000 Ohm Leakage Resistance test limit causing the Poor LED to be illuminated. That’s unfortunate because Leakage Current does not significantly affect coil performance unless it is very severe, well less than 1,000,000 Ohms. In hindsight, the capacitor Leakage Resistance test limit should have been set much lower to avoid confusion.
The bottom line is: Judge capacitors based on their Value, not Leakage Resistance. If the Capacitor Value tests greater than 0.33uF and less than 0.68uF it need not be replaced.