What are ECU capacitors & why it is important to replace them.

by Phearable Staff
Leaking Capacitors

What is a capacitor?

A capacitor is a passive two-terminal electrical component used to store electrical energy temporarily in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e. an insulator that can store energy by becoming polarized). The conductors can be thin films, foils or sintered beads of metal or conductive electrolyte, etc. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, air, vacuum, paper, mica, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of an electrostatic field between its plates.

When there is a potential difference across the conductors (e.g., when a capacitor is attached across a battery), an electric field develops across the dielectric, causing positive charge + Q to collect on one plate and negative charge −Q to collect on the other plate. If a battery has been attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor. However, if a time-varying voltage is applied across the leads of the capacitor, a displacement current can flow.

An ideal capacitor is characterized by a single constant value, its capacitance. Capacitance is defined as the ratio of the electric charge Q on each conductor to the potential difference V between them. The SI unit of capacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10−12 F) to about 1 mF (10−3 F).

The larger the surface area of the "plates" (conductors) and the narrower the gap between them, the greater the capacitance is. In practice, the dielectric between the plates passes a small amount of leakage current and also has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance.

Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage and power flow.

How long do capacitors last?

Aluminum electrolytic capacitors have a limited life span. Their life span is rated in hours + temperature.
For example, the factory C14 capacitor which is found in most obd1 honda engine computers is rated at 1,000 Hours @ 221 Degrees F.

Operating conditions directly affect the life of an aluminum electrolytic capacitor. The ambient temperature has the largest effect on life. The relationship between life and temperature follows a chemical reaction formula called Arrhenius' Law of Chemical Activity. Simply put, the law says that life of a capacitor doubles for every 10 degree Celsius decrease in temperature (within limits).

Voltage derating also increases the life of a capacitor, but to a far lesser extent, as compared to temperature deratings. Internal heating, caused by the applied ripple current, reduces the projected life of an aluminum electrolytic capacitor.

The changes in performance over time described as follows:
1. Eventually, the capacitance begins to drop off.
2. The tangent of the loss angle begins to increase.
3. Generally, when voltages are applied, the leakage current begins to drop.
4. Finally, at the end of the life span, the capacitor enters an open-circuit mode as the dielectric dries up.
5. Capacitor failure can ultimately lead to engine computer failure.

Should I replace the capacitors in my engine computer?

All Obd1 Honda engine computers are now over 20 years old. If the capacitors in your engine computer are original it wouldn't be a bad idea to replace the capacitors before you experience capacitor failure which can cause leakage & possible circuit board damage.

All Obd1 p28, p06, p05, p75, pr4 Chipped Engine Computers & Hondata S300 ECUS sold by Phearable.net since 1/1/2014 have had all of the primary capacitors replace. Prior to 1/1/2014 we replaced the primary ecu capacitor located at c14. If you mailed your ecu in for ecu chipping services, capacitor replacement is an option we offer as an addon.

Where can I buy replacement ecu capacitors or have my ecu's capacitors replaced?:
We offer an Obd1 ECU Capacitor Replacement Kit on our website and installation services.
To mail your ecu in for capacitor replacement services simply select the installation service option check box, click add to cart and complete your order via our shopping cart. Once you have completed the order you will be emailed with instructions on mailing in your engine computer.