Rick & Jake,
Eureka! Mystery solved. Just kept rereading your messages and was hard to believe, as you said, wiring short or wiring voltage drop. Noticed on schematic online for FRS24ZSGB0 that they had diodes and you can replace them with a diode kit. If one of diodes fails shorted, when either of the Chilled Water Dispenser at Front Door or the Icemaker is activated/cycled, the other also activates cycles. Of course this was not our problem. But if the icemaker diode fails open, then the steering current can't get to the icemaker solenoid so it doesn't activate and there is a voltage drop of between 20-30V which is like what we had. Thought that was our issue!
However, when i looked at the back, there was no diode pack to be found in the area of the solenoid. When i found the schematic for how diodes worked (attached) i realized that the diagram was for a triple solenoid inlet valve which had the one isolation valve for water from the wall (Brown connector/Solenoid). What we had was different, we had a dual solenoid water valve on the left hand side of the bottom of the fridge back (yellow for dispenser, green for icemaker both getting water source from the fridge side water filter and tank) and ANOTHER dual solenoid water valve on the right hand side of the bottom of the fridge back that brings in water from the wall and sends it to the filter through two solenoids whose water output is "Y" together. These Isolation Solenoids are strangely Yellow and Green, just like the Dual Water inlet Valve we replaced AND when i traced the blue wire providing 120 VAC from the Dual Water Inlet Valve, i saw it fed power to the Green Isolation Solenoid (see second picture attached.
My AHA moment was that our model was made before 2004-2005 when they tried to save money by going to one isolation solenoid and less wiring by using steering diodes. In our 1998 model, they used two solenoids instead of two diodes and energized both a green isolation solenoid AND the green icemaker solenoid when the icemaker called for water. Also, when someone wants water from the front door, since that happens with a separate Yellow and Yellow pair of isolation and chilled water solenoids, no problem. Secret is that the Water from either Isolation solenoid, since "Y"d together, go to the same place. To check this out, i disconnected the yellow solenoid connector and put the green connector from the green isolation solenoid to the yellow isolation solenoid, cycled the icemaker and water filled the tray for 7 seconds as hoped. This means that the green isolation solenoid had failed partially and would not deliver water to the other green solenoid and then to the icemaker. Since Appliance Parts Pro did not have the 218698900 Isolation Water Valve assembly, we are picking up from local appliance parts distributor Monday.
We've also include a picture of our Frigidaire and as you can probably see, not bad shape for a 23 year old appliance, hence why we wanted to keep it. Without help from you and Rick, we never could have figured this out. We're recently retired so thought of buying another fridge at this point was not a welcome expenditure. So, thanks for your assistance in keeping both our fridge AND our marriage running.
Gary and Kathy