John Deere 755c loader

[the loader guy]

Loader will not move forward or backwards. You reset the computer, the low light blinks once, the transformer light is off. When you pull the controller lever, the transformer light comes on immediately kicking the computer out. John Deere has been out and confirmed that all pump pressures are good, they are trying to get a test box but so far have been unsuccessful. Does anyone have any ideas? I have sent the computer out to another Deere dealer that has the test equipment about 2000 miles away from where the machine is located to have it checked for codes. I was told that the computer made a good strong connection and there was no stored codes.

 

[mg2361]

Welcome to HEF loader guy!

Do you have steering pedals? Your issue may be the pedal voltages are not correct. Is there dirt packed under them?

 

[the loader guy]

Deere did find the test equipment looks like the right steering pedal is out of spec he tried adjusting it it showed good the minute we reset the computer it show middle range did it 4 times it was middle range so he thinks it's the sensor what's your thoughts?

 

[mg2361]

Could be. I have replaced quite a few of those sensors.

 

[the loader guy]

John Deere came back out today replaced the foot pedal sensor didn't fix it. They did check the computer codes got 112 code if I remember correctly high voltage the alternator is putting out 28.6 volts so it's going in to shut down because it's out of spec they checked wires said they where good. With the red wire off the alternator he tried moving it still wouldn't move. The battery passed load check could there still be something wrong with the battery?

 

[mg2361]

28.6 is too high. That will shut the TCU down. I think he will need to clear the code, then try it with the alternator disconnected, or with a new alternator.

Yes, a bad battery could lead to overcharging. Also, what was the static voltage of the batteries both before and after the load test?

Did he use the pedal box to adjust the pedal sensor? Those sensors have a real tight tolerance and are finicky as heck to adjust. If he did not use the pedal box, then he might be fighting two issues at once.

 

[the loader guy]

The batteries did check out. I was told to leave the computer unplugged for a couple days so I did. I plugged it back in today left the alternator unplugged. It didn't move, then tapped on the computer box then it moved. It stopped a couple times I pushed both steer pedals down it would release the brakes and now it's driving fine without the alternator. What's your thoughts?, this thing is driving me crazy. I've got 15k into it so far with John deere they are mostly just throwing parts at it hope it sticks they wanted to put 20k computer in it without the voltage being correct.

 

[mg2361]

It stopped a couple times I pushed both steer pedals down it would release the brakes and now it's driving fine without the alternator.

I would try a new alternator and see if the issue returns. Way less expensive than a controller.

What's your thoughts?

Not being there to diagnose, I cannot commit to any particular solution. Tapping on the controller to make it go concerns me, and those TCU's have been problematic. However, I would not want to commit to a $17,000 controller (plus labor because it is a retrofit kit that requires special programming) without being sure. I would make sure the voltage issue is addressed first. I would have made sure those pedal adjustments were spot on, connections to the TCU in excellent shape.

You might consider looking for a working TCU from a scrap machine. Just have to make sure the serial number break is the same as yours. The controllers are either for serial number 6199 and down, or 6200 and up.

 

[the loader guy]

We put a new alternator in now reading 28.3 volts the grounds are good and positive cable is good still out of spec John Deere is talking about putting a resistor in what's your thoughts? Just seems odd to me didn't need one before. the alternator was bought from John Deere. Made in China

 

[mg2361]

If all the power input (engine running) to the controller measure 28.3 volts or less (measured by backprobing), and the ground measures 0.100 volts or less, then it is most likely an issue with the voltage stabilizer within the controller. They can try a resistor. It might work.

 

[the loader guy]

I found a 27.5 regulator Deere said it could not be over 27.5 it's now charging 27.3. so lesson learned to me make sure voltage is correct it also toasted my cooling fan computer thanks for your help I think my tcu over voltage is weak from being hit with over voltage so much thank you again for your help

 

[the loader guy]

Ok loader worked today but at the end of the day it stopped moving again it trips the computer if u go past the turtle on the v pattern if I stay turtle or less it will drive forward and backwards but if i go past turtle the red light comes on and it stops.i found if I hold the left pedal down after going it will go full tilt forward or reverse turning if I release the pedal it stops I can repeat it over and over whats your thoughts?

 

[mg2361]

The red transistor light or the red light in front of you above the windshield? I would be checking for codes again. On those machines, I always suspect pedal adjustments. They need to be perfect.

 

[the loader guy]

Deere came back out replaced the left pedal sensor now we got a 212 code short circuit park brake what do u think. it will drive on test box and TCU it just trips the transformer light

 

[mg2361]

It drives on the test box because the TCU is taken out of the equation. It quits with the TCU because of that park brake solenoid code. Park brake circuit needs to be checked out.

Check your messages.