Would you please let me know if you ever measured the frequency?

I am trying to replace a monovalve in my car with a more reliable ball valve. The problem is, the ball valve is quite slow. It takes 3-5 secs to open or close. If the pulsation rate of the normal monovalue is faster than about 0.2Hz then the ball valve would not be able to open or close fully before the next state change occurred.

It might be possible to use a small circuit to measure the duty cycle of the signal normally sent to the monovalve and output a signal with the same duty cycle but a much lower frequency. That would allow the ball valve to control total energy delivered to the heater core in approximately the same way.

This is all academic of course if the pulsation rate in the existing circuit is slow enough.