Quote:
Originally Posted by NiftySVX
So, you're saying the duty solenoid is operated by the current to the solenoid, not the voltage, which was my original theory before examining this circuit with a volt meter. If this is the case, then why do I observe a large voltage change at the green/yellow wire coming out of the TCU and one coming across the green/red wire to the resistor? and what circuit is in place between the two that regulates it to a constant voltage? Is this the purpose of the dropping resistor?
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Yes the voltage is always switched between zero volts and 12 volts, its the length of time that it is switched to full voltage that controls the current that flows. A shorter time reduces the current.
There are two square wave signals of the same phase, that operate the A solenoid. The one from the TCU to the dropping resistor, green/yellow is a 0 to 12 volt duty cycle square wave, that tells the trans how much load is applied to the box by the throttle.
The other is the green/red that is a 0 to 5 volt duty cycle square wave, that is used by the TCU to reduce line pressure for shifting, oil temp, etc.
The dropping resistor is between the two signals to allow them to have opposite duty cycle on times, without one shorting the other.
Eg. when the throttle is on the floor, it's on time is 5% for full line pressure. If a gear change is to take place the TCU will send a cycle on time of, say, 50% to reduce the line pressure. If the resistor was not there the lower on time, would short out the higher on time.
To be able to use the resistor to do this, the throttle signal is a higher voltage, the resistor reduces this to lower 5 volt.
Harvey.