Old dual temp bunker one end rises up in temp other ok need help!!

I have a dual tip bunker running on a rack. I had a problem with one of the ends at 6 foot section flooding back due to a bad check valve I replace the check valve always well for 3 to 4 days then noticed it was going into alarm for up to three hours the temperature would go from -9.5f to 34f Then it would randomly come back down on its own or just as it was going into a defrost this led me to think that maybe the TXV power element was bad. I poured a little bit of hot water on the bulb. In the case started running again before I did this my suction temperature was 32f suction was 20psi. I figured the TX V had to be replaced as it was an old model and I could not get parts for it at my local supplier so I replaced it with a sporlan valve, manufacture said it was 330btu per foot of coil, so I built a txv for this. I adjusted my superheat about 7-5f The case ran great for 3 days then went back into alarm . So I wondered if my solenoid coil was dropping out I replaced my coil the next day the same problem happened as I was in the store I put my coil magnet on the solenoid nothing happened so I put some hot water on the TXv bulb once more case started to flow. Running out of stuff to replace in this case I remove the guts out of the solenoid valve and replace the ball valve as it was an old-style Canabalt that I have seen snap partially shut a times so I have eliminated/rebuild all things in this case including the fan snap disk yet this case still does the same thing does anyone have any other suggestions TXV bulb us mounted on 7/8 pipe at 2o clock ish bright tight and clean, rinks great when it runs, coil is always Clear,

Added note: liquid header going into the case goes up one size then tees off to each case and draws it has under the gas header in the case, the circuit is centered on the rack so liquid press is ok at 175 psi when this happens, and same pressure when it's running fine, no other cases are doing this.

Did the TEV also get warm even you poured water over bulb indicating moisture?

I made sure to only put water on the bulb to try and isolate the problem. I wondered if there might be moisture in the txv as well, what's odd is the case is doing the same thing it has been sin July 2015( we just took this store over last summer) it appears to be getting worst. Which made me think that the peer element was the main problem, now having swapped out the txv power element, txv cartridge and body for new ones I figured I'd cover all my bases, the filter drier has also been removed for tested purpossss as a means to eleminate possibilities. Do you think what moisture in the valve would leave or melt at random times and allow normal operation up to 3 days? Thanks

Yes, it could be a bit random. Have seen that once before.

Hi Moe
What model of TEV have you fitted . Is it an MOP type as may be getting charge reversal taking place. ?Have you electric or hot gas defrost ?

It's a sporlan sbqe body, with z charge for 404 element and a aaa cartridge. And it's hot gas defrost.

Hi Moe
I think you may have a charge reversal situation but it is not clear from the photos where the hot gas defrost is injected into the coil. With an MOP type of TEV the charge in the bulb is very small and can under certain conditions leave the bulb and enter the valves power assembly. At this time its under what is called charge reversal. The bulb is the control point for the valve ,but if the charge migrates into the valve power head the valve will not open, ie it will be forced closed. This situation occurs when the bulb becomes hotter than the valves power assembly. If the defrost hot gas comes into the evaporator and heats up the pipe where the bulb is strapped, the charge in the bulb will be forced out by this heat and will go to the colder valve body /power element. After the defrost terminates the solenoid opens to let refrigerant into the TEV and evaporator, but the pressure from the bulb cannot overcome the gas pressure in the evaporator as the charge is in the valve head. The charge will slowly migrate back to the bulb when the defrost heat has gone away. In this case the bulb must be moved to a point on the suction pipe away beyond the point where the hot gas comes into the suction line ,so that the bulb is not heated during the defrost cycle. If you cannot move the bulb upstream of the hot gas injection point you can change the valve to a non MOP type such s a Danfoss N Range valve as they are none MOP and should not have this reversal problem . If you can take more pics of the evaporator showing the hot gas entry point that will help to confirm if this is the problem best regards

i see what you are saying And understand it. And we have so many of these valves our there running fine... To answer you ? with all the racks we operate the hot gas in this situation is injected at the suction line just above the epr on the rack it self so we dump hot gas in the suction and it back feeds the suction line in reverse flow and exits the coil at just before the txv. After that we go pass a check valve that is set to block flow during refrigeration(so we don't dump in metered gas in the Evap coil) and the hot gas bypasses the cases had valve and it returns to the liquid header for that cases, from there we go back to the rack, were it enters a defrost hot gas dump line to be sent to the roof and be condensed. After we end the defrost the hot gas sol. Valve closes, the suction epr is opened after the drop time expires and we return to refrigeration. Hope this show more light. Martin

Update: I starve the cool with the txv, I opened it some and left it while j did work came back to it kept opening till I got my case temp of -10f, I left the gauges and temlbprob jn te truck lol, she's never ran so good!