Found a manual for the system and it looks like good info:
I may not be spotting the exact correct model as your picture doesn't match what they show exactly but it seems the part/wires involved are the same on different models, so perhaps it is something you can use. Sometimes comparing what you see in the manual matches better than what I "think" from here!
So maybe see if this helps?
It sounds like two things are possible, so to start the chase, I go for the easier. First thought is that the solenoid to dump air may not be getting a good electrical signal to open. So it is corroded wire connections as the easier. Solenoid getting signal but defective? Or is it bad controls to send that signal from the control requiring control change? I would check wiring and solenoid as first option.
This manual shows the whole wiring layout but I have snipped a portion here to talk about:
Maybe take a look at the different manual parts to find the one which matches your system and to get an idea of the whole but this seems to be my plan.
Find a set of plugs as shown and tap into the green wire for the dump valve? I sometimes find pushing a pin through the insulation to get contact for the meter probe is one way to go if I need to have access but leave the rest of a plug connected? Depends what type plug you find? Depending on what you find, battery or ground when not trying to dump, I set the meter to look for change when I call for dumping.
Watch to keep clear when dumping!!!!
If I see a change from what first found, that says the signal is getting there and I go left to solenoid to confirm it is good or bad if getting signal all the way there!
If no signal at this first plug, perhaps look for a second plug or move to right in drawing until I find signal changes or confirm bad control head?
Far easier to write up the idea than to do the work, so I will wish you luck and let you tell us what you find?
