Electronic – Switch from electolytic to ceramic capacitors in car ECU


I'm looking into replacing the capacitors in the vehicles ECU. I know the ratings and voltages for the three. My question though is which would be better to go with, electrolytic or ceramic. I'm not worried about price of the caps just would like to know which would be the most reliable and will last.

The capacitors are:

  • 22µF 50V
  • 47µF 50V
  • 100µF 25V

Also if it helps it's for a 1996 Mitsubishi Galant VR-4 RHD.

I've read through Can I replace all electrolytic capacitors with ceramic ones? but didn't really answer my question unfortunately.

Thanks for any help.

Best Answer

Capacitor selection involves a lot more engineering than just voltage and capacitance. Your plan could make the circuit worse instead of better.

High value ceramic caps are fragile, and have a dangerous failure mode in automotive applications: When they crack, they tend to become a low-value resistor. An automotive power system can supply high currents into this low resistance, dissipating enough power to start a fire. You can get special "automotive" capacitors, but inside they are just two capacitors (of twice the capacitance) in series, so that both have to fail before the fire starts. I expect you will find better cost and availability to just put two in series in your circuit.

High value ceramic caps are fragile. Some manufacturers only recommend placement with reflow, not with a iron that heats each end individually. Don't expect great reliability if you hand-solder the caps in there.

I would think high-temperature electrolytic capacitors should last the life of the vehicle. Replace, if you have to, with good-quality ones. But the designers of the ECU were designing it to last and you can assume they chose the capacitors wisely.