4890 Rear Steer Problem

John Saeli · Jun 4, 2015

In front wheel steer, rear wheels swing fast to the right & loads the relief valve. In 4 wheel steer, switch to the left, in a hard right turn, the rear wheels will come back some. With the switch to the right, I can control the rear wheels with the toggle switch, and they will stay where I put them.
I checked voltages & grounds on the 1 - 10 wires, all good. I checked the rear harness, all OK.
Any ideas?

cnh · Jun 5, 2015

The first thing I always check is the filter screen in the rear steer valve. It has to be perfectly clean. From there I would closely inspect the potentiometers. Last time I checked these were still available, but terribly high priced, over $700.00 comes to mind. By loosening the front potentiometer on the bolts that secure it and turning it in its bore by hand, one should be able to get the rear wheels to react some. If I remember correctly the front potentiometer is used to center the rear wheels, but I may be mistaken as it has been a couple years since I played with these systems now.

John Saeli · Jun 5, 2015

I didn't do anything with the front, I focused on the rear. Thank you for the suggestions.

4435 · Jun 5, 2015

John: Can you, have you connected test lights and or a volt meter to the force motor or the wiring at the control panel to see if you are getting feed to the motor at the wrong time. I used a couple 12 volt marker bulbs and three wire set up with one wire being a common feed to the bulb ground side. Tom

Have extra pots if you need one.

John Saeli · Jun 5, 2015

I pulled the screen, it was clean, but it is cleaner now. Pulled the valve, blew out the orifices & re-installed. Still not working correctly. Did not do the voltage check you suggested yet, but suppose the force motor is getting signals when it is not supposed to? How would I fix that?

Eagle Doc · Jun 6, 2015

When the selector switch is in crab steer mode neither potentiometer is "active".
When the selector switch is in front steer only mode the rear potentiometer is active to keep the rear wheels straight.
When the selector switch is in coordinated mode both front and rear potentiometers are active.
I hope this helps.

John Saeli · Jun 6, 2015

Appreciate that explanation, but I still cannot figure out what is going on here.

Eagle Doc · Jun 6, 2015

This is just a guess, but it seems that the rear potentiometer is bad.

4435 · Jun 6, 2015

John; I concur with eagle doc. Although I am not certain it is the rear pot. Is the rear sensor assembly tight where the 1/4 set screw holds the lower body check the front also.
With the rear wheels moving in front only position and not stopping it could be also an open in the pot not feeding back to the brain telling the force motor what to do. Have you checked continuity when the wheels are at the right locked spot.
Probably not the problem but have you checked the hydraulic pressures at the rear steer valve. Tom

4890 Rear Steer Problem

John Saeli

Well-known Member

cnh

Member

John Saeli

Well-known Member

4435

Member

John Saeli

Well-known Member

Eagle Doc

Member

John Saeli

Well-known Member

Eagle Doc

Member

4435

Member

Similar threads