CTL machine throws this code intermittently and ceases to allow movement of tracks. Sometimes letting the machine sit or repeating the start up routine gets the tracks moving again. 4754 code is for the right hydrostat, 4752 is for the left side. There are a handful of HEF threads on this issue but most end up as dead ends. This one goes pretty far to get to the bottom of things: HeavyEquipmentForums In the operation manual there is a list of codes and these two codes come with an asterisk explaining that Cold hydro fluid can trigger these codes. 1. Why, how? 2. Could water in the fluid trip the code in the same manner as cold fluid? The machine has milky fluid...
Here is the Bosch Rexroth A22vg pump that feeds the drive motors. I think it's used in a lot of compact machines with tracks or tires including Case, Bobcat, Cat. This tr270 uses electrohydraulic EH control to tell the Rexroth what to do. https://www.hydropart.ru/upload/files/adaba7851c04702afafc985560c3b447.pdf If I understand things, the joystick sends a signal to the GCU to request drive motion. The GCU sends a signal x to the solenoids on the Rexroth to stroke the swash plate piston. A sensor on the swash plate pivot sends a signal y back to the GCU to tell it how much swivel angle the plate is sitting at. The GCU then compares x to y and sets a code if the comparison is "implausible". The drives get shut down for safety's sake in case the machine might be moving on its own, as is described in the HEF thread linked above. 3. Am I missing any steps or components in the chain of command that could be points of failure?
I'm slowly working my way through the issue but if I were to jump to throwing a new sensor at it, I see a Case sensor is over $700 but a Bobcat sensor is less than $400. hmmm, they look pretty similar... New Holland #84356794 SENSOR SWASH PLATE ANGLE SENSOR. SCREWS ARE NSS PROCURE LOCALLY. www.messicks.com Swash Plate Sensor for Track Loaders, 46891390 Swash Plate Sensor for Track Loaders, 46891390 is part of the hydrostatic pump 7509445 for selectable joystick controls (SJC). Parts can vary depending on your serial number. Use the Serial Number Parts Finder above or check the Bobcat Online Parts Catalog to ensure the correct part for your... shop.bobcat.com
As I slowly work through this I am learning a lot and have answered for myself questions 1 and 2. Changing the fluid hasn't eliminated the codes. I think the joysticks might be ok since the code gets set in both ISO and H joystick scenarios. Looking at the pics of the swash angle sensors, the mounting tabs have slots that allow "clocking" of the sensor. I assume this allows the sensors to be calibrated or zeroed. The sensor in question on this machine is rotated much more in the slots than the other one not triggering codes. Since I still need to learn anything about Case diagnostic software and calibrating this system, 4. Is there any point in trying to eliminate the code by changing the sensor clocking?
This issue has been frustratingly intermittent. I lucked out yesterday as after an hour of normal operation, it threw the code and shut down. I found that I could trigger the shutdown in H mode by just pulling the Left joystick towards reverse. As soon as the track started to creep, shutdown city. Repeatable. Time to change the sensor clocking. Twisted it all the way clockwise. Machine worked for a couple of joystick pull before shutting down. Now I can't get it to reset itself at all. Twisted it all the way counterclockwise. Machine threw code at start up without pulling any joysticks at all, again impossible to reset. Twisted the sensor to the center of the adjustment arch seems to have made the machine happy, at least for the 90 minutes i worked it.
Today code came back within 2 minutes. Adjusting the sensor by feel failed. Removed sensor because some suggestions were to clean the sensor for whatever reason. Backprobed the sensor connector to set position by voltage. Supposed to be 2.5 volts at "neutral" when powered up. Did that but left the wires hooked up so I can watch the sensor output as I operate the machine. In the meantime I learned that a crappy nylon bushing might actually be the cause for all this