34700z will not clear system and will not drain oil... Also can not get filter to clear for a filter change...

You confirm it by how it functions, if it sticks in a mechanical way there is no electrical testing that would be valid. I would just replace both solenoids.

To clean contaminated ISV of Robinair 34700Z, open front lower panel, then slowly disconnect 3 hoses from ISV (Liquid, Air purge and Vapor). Now unscrew ISV tank from machine and then fixed an adapter to Liquid port of the tank to allow all the contaminated refrigerant to go out from tank. after emptying the tank, if possible make vacuum for approx. 10 minute with an external vacuum pump. Replace everything its original location after completing vacuum. Now change spin-on filter (Located on the back side of the machine) and vacuum pump oil. Your machine is now ready to work.
Thanks and I hope this will help you to solve your problems.

your recycle solenoid is stuck open. the oil drain switch works by building pressure up to 16 psi then the recycel solenoid shuts off and the oil drain solenoid opens. if the recycle solenoid is stuck open you will get liquid 134 out when it is draining

For change vacuum pump oil follow the bellow step: Press main menu then keep pressing up or down arrow key till display show "CHANGE VACUUM OIL" then press "YES" key. Now vacuum pump will run for two minute & stop automatically. When pump stop you just open the oil drain cap and drain all used oil from pump (oil drain cap located outside of the machine near high & low side hose). After draining all used oil replace oil drain cap and fill 5 ounce new ROBINAIR vacuum pump oil then press "YES" key and keep filling oil up to middle of sight glass of vacuum pump. Press "STOP" key to complete the process.

NOTE: Do not over fill the pump & do not use any COMPRESSOR oil on the vacuum pump!
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YOU NEED TO REBUILD OR CHANGE OIL DRAIN SOLENOIS

Please check 1# OIL DRAIN solenoid, 2# OIL DRAIN switch, 3# OIL DRAIN CHECK valve. It sound like one of those are faulty.
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Check ISV tank liquid & vaipor hose.make sure it is not too much tight or lose. also check recovery,recycle & oil return solenoid are opening properly.

Pls Check oil drain solenoid it's may need to rebuild or replace.If solenoid is OK then you may need to change oil drain switch.

I don't think your machine have any problem! But if you are sure then you can rebuild oil drain solenoid.

You have to change/rebuild oil drain solenoid & check oil drain check valve.