Just installed the Yolink device and hub that @Greg Pack linked in this thread, to email me when a customers automatic goes out of service. Works perfectly!
I've personally never used 3/8" check valves, but I can't see them making any noticeable flow difference. Especially being mounted right above the boom.
Glad you got your issue resolved and back to working properly. Also, thanks for reporting back to everyone, (especially those who commented with advice on what to check) on what you did to fix your problem.
Randy, you would be correct. Old Magic Wand self serve bench. I would definately buy the valve you referenced instead of the Asco one. Only reason he would need the valve at all, is if he is using hot water for soap and wax. If it is cold water in the gravity feed reservoir tank for soap and...
Are you running hot water for soap and wax that pulls from the stainless steel holding tank? If the answer is no, you don't even need that 1/2" Asco Valve.
Brass 2-Way N.O. Solenoid, 1/2” NPT, 125PSI, 24VAC|ASCO|8210G034 (kleen-ritecorp.com)
You've got to have a mercury relay or some type of contactor under the dome on top. Can you take the blue dome off and take a picture? When you jumped terminals 1 & 2, you bypassed the timer.