PWM soleniods: failure due to wear
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1. As seen in other pictures, the sealing areas of solenoids can just wear out.
2. Wear will result in:
- Increased armature stroke
- Longer solenoid response times
- Sealing problems
- Changes in solenoid performance
The graph shows how excessive wear changes the solenoid's ability to control output pressure. Poor material selection and improper machining were the cause.
3. F4E-III PWM EPC solenoid and VB
Yellow represents oil from solenoid; blue is output oil.Close-up of the spool shows the spring has ground itself into the spool which used to be flat. Wear can be seen on the end of the spool. A close-up of the spool edge shows how the once sharp corner is now beveled.
4. Normal function of F4EIII
Main line pressure is reduced through the solenoid modulator valve: around 60 psi. (not shown). With the solenoid off, pressure travels through the spool where it will effect the main pressure regulator valve. When the solenoid is cycled, the flow through the valve is limited, lowering the pressure output to the main regulator valve.
5. If the solenoid seat is worn out and leaks, pressure may never build high enough. If the spool is worn and leaking, pressure may remain too high!
6. Signs of wear: None! For possible spool wear consider:
- Condition of oil
- Condition of filter
- Vehicle mileage, driving conditions
- Life for PWM type solenoids (45 hz, =162,000 cycle/ hr X 2000 Hr ( 100, 000 miles @ 50 MPH) =324,000,000 cycle)
Click on an illustration to see an enlargement.
© Scott Kirkendall
Other related articles:
On-off solenoids: Failure due to contaminationOn-off solenoids: Failure due to wear
On-off solenoids: Failure due to abuse
On-off solenoids: Failure due to heat
On-off solenoids: Failure due to electrical causes
PWM solenoids: Failure due to contamination
PWM solenoids: Failure due to abuse
PWM solenoids: Failure due to heat
Proportional solenoids: Failure due to contamination
Proportional solenoids: Failure due to wear
Proportional solenoids: Failure due to abuse
Proportionalsolenoids: Failure due to heat
Replace and reuse rules
Failure review chart