NH 2120 HSS No Forward or Reverse, How do I check/adjust the pressure relief valve?

[grcutter]

Thanks for posting the control box test. I ended up purchasing the service manual as I can see that I may eventually need a lot more of it's pages.

Here is the latest with my problem: The slipping into neutral is occurring randomly (or at least I have not been able to detect what triggers it).
While it is in this state, going to higher rpm does not help or do anything but dropping down to really low rpm, like 1000, and it will slip back into motion.
Once it is back in motion (either forward or reverse) I can rev up the rpms and start to use the tractor normally again until the next time that it goes back into neutral.

A local guy suggested that this may be fluid related and that at high rpm there may be less fluid available for the HSS or there could be an air leak.

Would either of these explanations make sense?

 

[chander]

It possibly sounds like the pressure relief valve is opening. By lowering the RPM's that decreases the hydraulic pressure and allows the relief valve to close.

You performed the flow test at 7l per minute. With that test, that proves there is enough fluid to the clutches.

I would check the pressure relief valve pressure next. If the pressure looks normal, I would use the tractor with the gauge attached and monitor the pressure.

Could you attach you volt meter to the forward coil and use the tractor? With the meter attached, when the problem happens, look at the voltage. Could there be an intermittent problem with the control box?

 

[Mpf33]

It possibly sounds like the pressure relief valve is opening. By lowering the RPM's that decreases the hydraulic pressure and allows the relief valve to close.

You performed the flow test at 7l per minute. With that test, that proves there is enough fluid to the clutches.

I would check the pressure relief valve pressure next. If the pressure looks normal, I would use the tractor with the gauge attached and monitor the pressure.

Could you attach you volt meter to the forward coil and use the tractor? With the meter attached, when the problem happens, look at the voltage. Could there be an intermittent problem with the control box?

So I’m literally have the same exact situation on mine, 1999 Ford 2120. I have been trying every combination of odd “inputs” to see what could be triggering it. I did notice today that if I put the lodes bucket down against the ground and lifted up the front tires a bit, it would engage. So I think the last comment could have some merit that there is some imbalance in the hydraulic system and maybe the relief valve is staying open? The only way to tell would be to put an external relief valve with a hose back to tank and monitor that. I feel like if it was purely electrical it would be consistent and would all of a sudden work again, since there are no broken wires, shorts, etc. (Though it’s possible in the control module). A stuck relief valve would make sense because if there is voltage to the coils, and nothing happens, either the entire spool isn’t moving, or there is literally no pressure.

 

[grcutter]

Hi Mpf33,
Have you resolved this problem from September 2022 or is it still ongoing?
In the end, my problem ended up being an intermittent Forward/Neutral/Reverse switch and a bad Amperage Controller box.
Here is a link to some information about the Amperage Controller box (if you have one):

Ford/New Holland 2120 w/EHSS. Does anyone know what the Amperage Controller box does?

I have a 2001 Ford/New Holland 2120 with EHSS that is giving me intermittent neutral problems. I have traced all the wiring and came across a mysterious small black plastic box that is in between the shuttle shifting switch and the EHSS controller box. I can not find this box on any schematic...

www.tractorbynet.com

There is also a common issue with the main diode inside the EHSS controller box itself.
Here is the link to the diode issue: 2120 HSS command will not engage forward or reverse