PWM soleniod failures
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1. Normal PWM operation shows a square wave, duty cycle.
2. Peak and hold signals.
The graphic shows the normal operation of this PWM circuit. With solenoid off, full pressure is allowed to enter the KS and FC. When the solenoid is pulsed, pressure to the KS and FC gets lower. Reduce pressure during the shift for a smoother feel.
3. Actually there is not as much movement to the spool. Rather, it oscillates back and forth, allowing small amounts of pressure into the KS and FC circuits.
4. Failures are around 24 %, not that contamination is less of an issue in PWM solenoids. It just leads to other types of failures.
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!
Heat failures are 22 %. PWM solenoids generate more heat than On/ off solenoids. Most of the failures are due to wear. Wear is greatly effected by the level of contamination. 6 % are abused, and 4 % fail due to bad coils.
© 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
PWM solenoids: Failure due to wear
Proportional solenoids: Failure due to contamination
Proportional solenoids: Failure due to wear
Proportional solenoids: Failure due to abuse
Proportional solenoids: Failure due to heat
Replace and reuse rules
Failure review chart